diff --git a/staff/agustin-birman/api/logic/activity/deleteActivity.spec.js b/staff/agustin-birman/api/logic/activity/deleteActivity.spec.js
index 19a3952ed..77c0f0ea0 100644
--- a/staff/agustin-birman/api/logic/activity/deleteActivity.spec.js
+++ b/staff/agustin-birman/api/logic/activity/deleteActivity.spec.js
@@ -7,7 +7,7 @@ import { expect } from 'chai'
 import { User, Activity } from '../../data/index.js'
 
 import deleteActivity from './deleteActivity.js'
-import { ContentError, NotFoundError } from 'com/errors.js'
+import { ContentError, MatchError, NotFoundError } from 'com/errors.js'
 
 const { MONGODB_URL_TEST } = process.env
 
@@ -31,14 +31,42 @@ describe('deleteActivity', () => {
             })
     })
 
+    it('fails on non-matching user', () => {
+        let errorThrown
+
+        return bcrypt.hash('12345678', 8)
+            .then(hash => Promise.all([User.create({
+                name: 'Mocha',
+                surname: 'Chai',
+                email: 'Mocha@Chai.com',
+                username: 'MochaChai',
+                password: hash,
+                userType: 'teacher'
+            }), User.create({
+                name: 'Test',
+                surname: 'User',
+                email: 'test@user.com',
+                username: 'testuser',
+                password: hash,
+                userType: 'teacher'
+            })]))
+            .then(([user1, user2]) => Activity.create({ teacher: user1.id, title: 'title', description: 'description' })
+                .then(activity => ({ user1, user2, activity })))
+            .then(({ user2, activity }) => deleteActivity(user2.id, activity.id)
+                .catch(error => errorThrown = error)
+                .finally(() => {
+                    expect(errorThrown).to.be.an.instanceOf(MatchError)
+                    expect(errorThrown.message).to.equal('you are not the owner of the activity')
+                }))
+    })
+
     it('fails on non-existing user', () => {
         let errorThrown
 
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => deleteActivity(new ObjectId().toString(), activity.id)
+                .then(activity => deleteActivity(new ObjectId().toString(), activity.id))
                 .catch(error => errorThrown = error)
                 .finally(() => {
                     expect(errorThrown).to.be.an.instanceOf(NotFoundError)
@@ -64,8 +92,7 @@ describe('deleteActivity', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => deleteActivity(user.id, new ObjectId().toString())
+                .then(() => deleteActivity(user.id, new ObjectId().toString()))
                 .catch(error => errorThrown = error)
                 .finally(() => {
                     expect(errorThrown).to.be.an.instanceOf(NotFoundError)
diff --git a/staff/agustin-birman/api/logic/activity/editActivity.spec.js b/staff/agustin-birman/api/logic/activity/editActivity.spec.js
index c0ba316bb..6a7ad2656 100644
--- a/staff/agustin-birman/api/logic/activity/editActivity.spec.js
+++ b/staff/agustin-birman/api/logic/activity/editActivity.spec.js
@@ -21,10 +21,8 @@ describe('editActivity', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => editActivity(user.id, activity.id, 'title2', 'description2')
-                .then(() => activity))
-            .then(activity => Activity.findById(activity.id))
+                .then(activity => editActivity(user.id, activity.id, 'title2', 'description2')
+                    .then(() => Activity.findById(activity.id))))
             .then(activityEditted => {
                 expect(activityEditted.title).to.equal('title2')
                 expect(activityEditted.description).to.equal('description2')
@@ -53,8 +51,7 @@ describe('editActivity', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(() => user))
-            .then(user => editActivity(user.id, new ObjectId().toString(), 'title2', 'description2'))
+                .then(() => editActivity(user.id, new ObjectId().toString(), 'title2', 'description2')))
             .catch(error => errorThrown = error)
             .finally(() => {
                 expect(errorThrown).to.be.an.instanceOf(NotFoundError)
@@ -88,32 +85,26 @@ describe('editActivity', () => {
 
     it('fails on invalid title', () => {
         let errorThrown
-
-        return bcrypt.hash('12345678', 8)
-            .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
-            .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => editActivity(user.id, activity.id, 12345, 'description2'))
-            .catch(error => errorThrown = error)
-            .finally(() => {
-                expect(errorThrown).to.be.an.instanceOf(ContentError)
-                expect(errorThrown.message).to.equal('title is not valid')
-            })
+        try {
+            editActivity(new ObjectId().toString(), new ObjectId().toString(), 123, 'description2')
+        } catch (error) {
+            errorThrown = error
+        } finally {
+            expect(errorThrown).to.be.instanceOf(ContentError)
+            expect(errorThrown.message).to.equal('title is not valid')
+        }
     })
 
     it('fails on invalid description', () => {
         let errorThrown
-
-        return bcrypt.hash('12345678', 8)
-            .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
-            .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => editActivity(user.id, activity.id, 'title', 12345))
-            .catch(error => errorThrown = error)
-            .finally(() => {
-                expect(errorThrown).to.be.an.instanceOf(ContentError)
-                expect(errorThrown.message).to.equal('description is not valid')
-            })
+        try {
+            editActivity(new ObjectId().toString(), new ObjectId().toString(), 'title', 123)
+        } catch (error) {
+            errorThrown = error
+        } finally {
+            expect(errorThrown).to.be.instanceOf(ContentError)
+            expect(errorThrown.message).to.equal('description is not valid')
+        }
     })
 
     after(() => Promise.all([User.deleteMany(), Activity.deleteMany()]).then(() => mongoose.disconnect()))
diff --git a/staff/agustin-birman/api/logic/activity/getActivities.spec.js b/staff/agustin-birman/api/logic/activity/getActivities.spec.js
index e945f29e8..9d75f916a 100644
--- a/staff/agustin-birman/api/logic/activity/getActivities.spec.js
+++ b/staff/agustin-birman/api/logic/activity/getActivities.spec.js
@@ -23,8 +23,7 @@ describe('getActivities', () => {
             .then(user =>
                 Activity.create({ teacher: user.id, title: 'title', description: 'description' })
                     .then(() => Activity.create({ teacher: user.id, title: 'title2', description: 'description2' }))
-                    .then(() => user))
-            .then(user => getActivities(user.id))
+                    .then(() => getActivities(user.id)))
             .then(activities => {
                 expect(activities).to.be.an('array')
                 expect(activities).to.have.lengthOf(2)
diff --git a/staff/agustin-birman/api/logic/activity/getActivity.js b/staff/agustin-birman/api/logic/activity/getActivity.js
index 15a64c1b1..eaa55035f 100644
--- a/staff/agustin-birman/api/logic/activity/getActivity.js
+++ b/staff/agustin-birman/api/logic/activity/getActivity.js
@@ -17,6 +17,7 @@ const getActivity = (userId, activityId) => {
                 .then(activity => {
                     if (!activity)
                         throw new NotFoundError('activity not found')
+
                     const activityObj = activity.toObject()
                     activityObj.id = activityObj._id
                     delete activityObj._id
diff --git a/staff/agustin-birman/api/logic/activity/getActivity.spec.js b/staff/agustin-birman/api/logic/activity/getActivity.spec.js
index b44ce15bd..5e516227d 100644
--- a/staff/agustin-birman/api/logic/activity/getActivity.spec.js
+++ b/staff/agustin-birman/api/logic/activity/getActivity.spec.js
@@ -21,13 +21,12 @@ describe('getActivity', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => getActivity(user.id, activity.id))
-            .then(activity => {
-                expect(activity.teacher).to.equal(activity.teacher)
-                expect(activity.title).to.equal('title')
-                expect(activity.description).to.equal('description')
-            })
+                .then(activity => getActivity(user.id, activity.id)
+                    .then(activityInfo => {
+                        expect(activityInfo.teacher.toString()).to.equal(activity.teacher.toString())
+                        expect(activityInfo.title).to.equal('title')
+                        expect(activityInfo.description).to.equal('description')
+                    })))
     })
 
     it('fails on non-existing user', () => {
@@ -50,8 +49,7 @@ describe('getActivity', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(() => user))
-            .then(user => getActivity(user.id, new ObjectId().toString()))
+                .then(() => getActivity(user.id, new ObjectId().toString())))
             .catch(error => errorThrown = error)
             .finally(() => {
                 expect(errorThrown).to.be.an.instanceOf(NotFoundError)
diff --git a/staff/agustin-birman/api/logic/answer/deleteAnswers.js b/staff/agustin-birman/api/logic/answer/deleteAnswers.js
index e0744bbfe..0ab040cc5 100644
--- a/staff/agustin-birman/api/logic/answer/deleteAnswers.js
+++ b/staff/agustin-birman/api/logic/answer/deleteAnswers.js
@@ -20,14 +20,16 @@ const deleteAnswers = (userId, activityId) => {
 
                     return Exercise.find({ activity: activityId })
                         .catch(error => { throw new SystemError(error.message) })
-                        .then(exercise => {
-                            if (!exercise)
+                        .then(exercises => {
+                            if (!exercises || exercises.length === 0)
                                 throw new NotFoundError('exercise not found')
 
-                            return Answer.find({ exercise: exercise._id })
+                            const exerciseIds = exercises.map(exercise => exercise._id)
+
+                            return Answer.find({ exercise: exerciseIds })
                                 .catch(error => { throw new SystemError(error.message) })
                                 .then(answers => {
-                                    if (!answers)
+                                    if (!answers || answers.length === 0)
                                         throw new NotFoundError('answer not found')
 
                                     return Answer.deleteMany(answers._id)
diff --git a/staff/agustin-birman/api/logic/answer/deleteAnswers.spec.js b/staff/agustin-birman/api/logic/answer/deleteAnswers.spec.js
index 783d167f5..55fda0888 100644
--- a/staff/agustin-birman/api/logic/answer/deleteAnswers.spec.js
+++ b/staff/agustin-birman/api/logic/answer/deleteAnswers.spec.js
@@ -9,6 +9,7 @@ const { MONGODB_URL_TEST } = process.env
 
 const { ObjectId } = Types
 
+debugger
 
 describe('deleteAnswers', () => {
     before(() => mongoose.connect(MONGODB_URL_TEST))
@@ -40,7 +41,6 @@ describe('deleteAnswers', () => {
                                 .then(answer2 => deleteAnswers(user.id, activity.id)
                                     .then(() => Answer.find({ activity: activity.id })
                                         .then(answers => expect(answers).to.be.an('array').that.is.empty))))))))
-
     })
 
     it('fails non-existing user', () => {
@@ -77,6 +77,33 @@ describe('deleteAnswers', () => {
                                 }))))))
     })
 
+    it('fails non-existing exercise', () => {
+        let errorThrown
+        return bcrypt.hash('12345678', 8)
+            .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
+            .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
+                .then(activity => deleteAnswers(user.id, activity.id))
+                .catch(error => errorThrown = error)
+                .finally(() => {
+                    expect(errorThrown).to.be.an.instanceOf(NotFoundError)
+                    expect(errorThrown.message).to.equal('exercise not found')
+                }))
+    })
+
+    it('fails non-existing answer', () => {
+        let errorThrown
+        return bcrypt.hash('12345678', 8)
+            .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
+            .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(() => deleteAnswers(user.id, activity.id))
+                    .catch(error => errorThrown = error)
+                    .finally(() => {
+                        expect(errorThrown).to.be.an.instanceOf(NotFoundError)
+                        expect(errorThrown.message).to.equal('answer not found')
+                    })))
+    })
+
     it('fails on invalid userId', () => {
         let errorThrown
         try {
@@ -89,7 +116,7 @@ describe('deleteAnswers', () => {
         }
     })
 
-    it('fails on invalid userId', () => {
+    it('fails on invalid activityId', () => {
         let errorThrown
         try {
             deleteAnswers(new ObjectId().toString(), 123)
diff --git a/staff/agustin-birman/api/logic/answer/submitAnswer.spec.js b/staff/agustin-birman/api/logic/answer/submitAnswer.spec.js
index 335bfa7ef..a2a472f1e 100644
--- a/staff/agustin-birman/api/logic/answer/submitAnswer.spec.js
+++ b/staff/agustin-birman/api/logic/answer/submitAnswer.spec.js
@@ -7,7 +7,7 @@ import submitAnswer from './submitAnswer.js'
 import { User, Activity, Exercise, Answer } from '../../data/index.js'
 
 import { expect } from 'chai'
-import { ContentError, NotFoundError } from 'com/errors.js'
+import { ContentError, DuplicityError, NotFoundError } from 'com/errors.js'
 
 const { MONGODB_URL_TEST } = process.env
 
@@ -23,10 +23,8 @@ describe('submitAnswer', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                .then(exercise => ({ user, activity, exercise })))
-            .then(({ user, activity, exercise }) => submitAnswer(user.id, activity.id, exercise.id, 'hat'))
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(exercise => submitAnswer(user.id, activity.id, exercise.id, 'hat'))))
             .then(answer => Answer.findById(answer.id))
             .then(answer => {
                 expect(answer.answer).to.equal('hat')
@@ -39,10 +37,8 @@ describe('submitAnswer', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                .then(exercise => ({ exercise, activity })))
-            .then(({ activity, exercise }) => submitAnswer(new ObjectId().toString(), activity.id, exercise.id, 'hat'))
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(exercise => submitAnswer(new ObjectId().toString(), activity.id, exercise.id, 'hat'))))
             .catch(error => errorThrown = error)
             .finally(() => {
                 expect(errorThrown).to.be.an.instanceOf(NotFoundError)
@@ -56,10 +52,8 @@ describe('submitAnswer', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                .then(exercise => ({ user, exercise })))
-            .then(({ user, exercise }) => submitAnswer(user.id, new ObjectId().toString(), exercise.id, 'hat'))
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(exercise => submitAnswer(user.id, new ObjectId().toString(), exercise.id, 'hat'))))
             .catch(error => errorThrown = error)
             .finally(() => {
                 expect(errorThrown).to.be.an.instanceOf(NotFoundError)
@@ -73,10 +67,8 @@ describe('submitAnswer', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                .then(() => ({ user, activity })))
-            .then(({ user, activity }) => submitAnswer(user.id, activity.id, new ObjectId().toString(), 'hat'))
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(() => submitAnswer(user.id, activity.id, new ObjectId().toString(), 'hat'))))
             .catch(error => errorThrown = error)
             .finally(() => {
                 expect(errorThrown).to.be.an.instanceOf(NotFoundError)
@@ -84,27 +76,37 @@ describe('submitAnswer', () => {
             })
     })
 
-    it('fails on invalid answer', () => {
+    it('fails on existing answer', () => {
         let errorThrown
-
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                .then(exercise => ({ user, activity, exercise })))
-            .then(({ user, activity, exercise }) => submitAnswer(user.id, activity.id, exercise.id, 123))
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(exercise => Answer.create({ student: user.id, exercise: exercise.id, activity: activity.id, answer: 'hat' })
+                        .then(() => submitAnswer(user.id, activity.id, exercise.id, 'hat')))))
             .catch(error => errorThrown = error)
             .finally(() => {
-                expect(errorThrown).to.be.an.instanceOf(ContentError)
-                expect(errorThrown.message).to.equal('answer is not valid')
+                expect(errorThrown).to.be.an.instanceOf(DuplicityError)
+                expect(errorThrown.message).to.equal('Answer already exists for this exercise')
             })
     })
 
+    it('fails on invalid answer', () => {
+        let errorThrown
+        try {
+            submitAnswer(new ObjectId().toString(), new ObjectId().toString(), new ObjectId().toString(), 123)
+        } catch (error) {
+            errorThrown = error
+        } finally {
+            expect(errorThrown).to.be.instanceOf(ContentError)
+            expect(errorThrown.message).to.equal('answer is not valid')
+        }
+    })
+
     it('fails on invalid userId', () => {
         let errorThrown
         try {
-            submitAnswer(123, new ObjectId().toString(), new ObjectId().toString(), 123)
+            submitAnswer(123, new ObjectId().toString(), new ObjectId().toString(), '123')
         } catch (error) {
             errorThrown = error
         } finally {
diff --git a/staff/agustin-birman/api/logic/exercise/createCompleteSentenceExercise.js b/staff/agustin-birman/api/logic/exercise/createCompleteSentenceExercise.js
index afd697418..67e273527 100644
--- a/staff/agustin-birman/api/logic/exercise/createCompleteSentenceExercise.js
+++ b/staff/agustin-birman/api/logic/exercise/createCompleteSentenceExercise.js
@@ -7,7 +7,7 @@ const ANSWER_REGEX = /\(([^)]+)\)/;
 const createCompleteSentenceExercise = (userId, activityId, sentence) => {
     validate.id(userId, 'userId')
     validate.id(activityId, 'activityId')
-    validate.text(sentence, 'sentence', 200)
+    validate.textCompleteSentence(sentence, 'sentence', 200)
 
     return User.findById(userId).lean()
         .catch(error => { throw new SystemError(error.message) })
diff --git a/staff/agustin-birman/api/logic/exercise/createCompleteSentenceExercise.spec.js b/staff/agustin-birman/api/logic/exercise/createCompleteSentenceExercise.spec.js
index e8c04e384..b1a99a2b2 100644
--- a/staff/agustin-birman/api/logic/exercise/createCompleteSentenceExercise.spec.js
+++ b/staff/agustin-birman/api/logic/exercise/createCompleteSentenceExercise.spec.js
@@ -24,8 +24,7 @@ describe('createCompleteSentenceExercise', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => createCompleteSentenceExercise(user.id, activity.id, 'alan (hat) es gegessen'))
+                .then(activity => createCompleteSentenceExercise(user.id, activity.id, 'alan (hat) es gegessen')))
             .then(() => Exercise.findOne())
             .then(exercise => {
                 expect(exercise.sentence).to.equal('alan (hat) es gegessen')
@@ -40,8 +39,7 @@ describe('createCompleteSentenceExercise', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => createCompleteSentenceExercise(new ObjectId().toString(), activity.id, 'alan (hat) es gegessen'))
+                .then(activity => createCompleteSentenceExercise(new ObjectId().toString(), activity.id, 'alan (hat) es gegessen')))
             .catch(error => errorThrown = error)
             .finally(() => {
                 expect(errorThrown).to.be.an.instanceOf(NotFoundError)
@@ -55,8 +53,7 @@ describe('createCompleteSentenceExercise', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => createCompleteSentenceExercise(user.id, new ObjectId().toString(), 'alan (hat) es gegessen'))
+                .then(() => createCompleteSentenceExercise(user.id, new ObjectId().toString(), 'alan (hat) es gegessen')))
             .catch(error => errorThrown = error)
             .finally(() => {
                 expect(errorThrown).to.be.an.instanceOf(NotFoundError)
@@ -90,17 +87,14 @@ describe('createCompleteSentenceExercise', () => {
 
     it('fails on invalid sentence', () => {
         let errorThrown
-
-        return bcrypt.hash('12345678', 8)
-            .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
-            .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => createCompleteSentenceExercise(user.id, activity.id, 123))
-            .catch(error => errorThrown = error)
-            .finally(() => {
-                expect(errorThrown).to.be.an.instanceOf(ContentError)
-                expect(errorThrown.message).to.equal('sentence is not valid')
-            })
+        try {
+            createCompleteSentenceExercise(new ObjectId().toString(), new ObjectId().toString(), 123)
+        } catch (error) {
+            errorThrown = error
+        } finally {
+            expect(errorThrown).to.be.instanceOf(ContentError)
+            expect(errorThrown.message).to.equal('sentence is not valid')
+        }
     })
 
     after(() => Promise.all([User.deleteMany(), Activity.deleteMany(), Exercise.deleteMany()]).then(() => mongoose.disconnect()))
diff --git a/staff/agustin-birman/api/logic/exercise/deleteExercise.spec.js b/staff/agustin-birman/api/logic/exercise/deleteExercise.spec.js
index a8efea1f1..efade8b2e 100644
--- a/staff/agustin-birman/api/logic/exercise/deleteExercise.spec.js
+++ b/staff/agustin-birman/api/logic/exercise/deleteExercise.spec.js
@@ -5,7 +5,7 @@ import { expect } from 'chai'
 
 import { User, Activity, Exercise } from '../../data/index.js'
 import deleteExercise from './deleteExercise.js'
-import { ContentError, NotFoundError } from 'com/errors.js'
+import { ContentError, MatchError, NotFoundError } from 'com/errors.js'
 
 const { MONGODB_URL_TEST } = process.env
 
@@ -21,25 +21,34 @@ describe('deleteExercise', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                .then(exercise => ({ user, exercise })))
-            .then(({ user, exercise }) => deleteExercise(user.id, exercise.id)
-                .then(() => Exercise.findById(exercise.id)))
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(exercise => deleteExercise(user.id, exercise.id)
+                        .then(() => Exercise.findById(exercise.id)))))
             .then(exercise => {
                 expect(exercise).to.be.null
             })
     })
 
+    it('fails on non-existing activity', () => {
+        return bcrypt.hash('12345678', 8)
+            .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
+            .then(user => Exercise.create({ teacher: user.id, activity: new ObjectId(), sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                .then(exercise => deleteExercise(user.id, exercise.id)
+                    .catch(error => {
+                        expect(error).to.be.instanceOf(NotFoundError)
+                        expect(error.message).to.equal('activity not found')
+                    })
+                ))
+    })
+
     it('fails on non-existing user', () => {
         let errorThrown
 
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 }))
-            .then(exercise => deleteExercise(new ObjectId().toString(), exercise.id)
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(exercise => deleteExercise(new ObjectId().toString(), exercise.id)))
                 .catch(error => errorThrown = error)
                 .finally(() => {
                     expect(errorThrown).to.be.an.instanceOf(NotFoundError)
@@ -53,10 +62,8 @@ describe('deleteExercise', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                .then(() => user))
-            .then(user => deleteExercise(user.id, new ObjectId().toString())
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(() => deleteExercise(user.id, new ObjectId().toString())))
                 .catch(error => errorThrown = error)
                 .finally(() => {
                     expect(errorThrown).to.be.an.instanceOf(NotFoundError)
@@ -64,6 +71,35 @@ describe('deleteExercise', () => {
                 }))
     })
 
+    it('fails on different user', () => {
+        let errorThrown
+
+        bcrypt.hash('1234', 8)
+            .then(hash => Promise.all([User.create({
+                name: 'Mocha',
+                surname: 'Chai',
+                email: 'Mocha@Chai.com',
+                username: 'MochaChai',
+                password: hash,
+                userType: 'teacher'
+            }), User.create({
+                name: 'Test',
+                surname: 'User',
+                email: 'test@user.com',
+                username: 'testuser',
+                password: hash,
+                userType: 'teacher'
+            })]))
+            .then(([user1, user2]) => Activity.create({ teacher: user1.id, title: 'title', description: 'description' })
+                .then(activity => Exercise.create({ teacher: user1.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(exercise => deleteExercise(user2.id, exercise.id))))
+            .catch(error => errorThrown = error)
+            .finally(() => {
+                expect(errorThrown).to.be.an.instanceOf(MatchError)
+                expect(errorThrown.message).to.equal('you are not the owner of the exercise')
+            })
+    })
+
     it('fails on invalid userId', () => {
         let errorThrown
         try {
@@ -88,6 +124,5 @@ describe('deleteExercise', () => {
         }
     })
 
-
     after(() => Promise.all([User.deleteMany(), Activity.deleteMany(), Exercise.deleteMany()]).then(() => mongoose.disconnect()))
 })
\ No newline at end of file
diff --git a/staff/agustin-birman/api/logic/exercise/editExercise.spec.js b/staff/agustin-birman/api/logic/exercise/editExercise.spec.js
index b451fe503..a83e3e592 100644
--- a/staff/agustin-birman/api/logic/exercise/editExercise.spec.js
+++ b/staff/agustin-birman/api/logic/exercise/editExercise.spec.js
@@ -22,11 +22,9 @@ describe('editExercise', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                .then(exercise => ({ user, exercise })))
-            .then(({ user, exercise }) => editExercise(user.id, exercise.id, 'ich (habe) es gesagt')
-                .then(() => Exercise.findById(exercise.id)))
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(exercise => editExercise(user.id, exercise.id, 'ich (habe) es gesagt')
+                        .then(() => Exercise.findById(exercise.id)))))
             .then(exercise => {
                 expect(exercise.sentence).to.equal('ich (habe) es gesagt')
                 expect(exercise.answer).to.equal('habe')
diff --git a/staff/agustin-birman/api/logic/exercise/getExercises.spec.js b/staff/agustin-birman/api/logic/exercise/getExercises.spec.js
index a1a16c240..ce4a44f00 100644
--- a/staff/agustin-birman/api/logic/exercise/getExercises.spec.js
+++ b/staff/agustin-birman/api/logic/exercise/getExercises.spec.js
@@ -20,33 +20,27 @@ describe('getExercises', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) =>
-                Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                    .then(() => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'pepe (hat) es gesagt', answer: 'hat', index: 1 }))
-                    .then(() => ({ user, activity }))
-            )
-            .then(({ user, activity }) => getExercises(user.id, activity.id)
-                .then(result => ({ activity, result }))
-            )
-            .then(({ result, activity }) => {
-                const { exercises, count } = result
-
-                expect(exercises).to.be.an('array')
-                expect(count).to.be.a('number')
-
-                expect(exercises).to.have.lengthOf(2)
-
-                expect(exercises[0].activity.toString()).to.equal(activity.id)
-                expect(exercises[0].sentence).to.equal('alan (hat) es gegessen')
-                expect(exercises[0].answer).to.equal('hat')
-                expect(exercises[0].index).to.equal(0)
-
-                expect(exercises[1].activity.toString()).to.equal(activity.id)
-                expect(exercises[1].sentence).to.equal('pepe (hat) es gesagt')
-                expect(exercises[1].answer).to.equal('hat')
-                expect(exercises[1].index).to.equal(1)
-            })
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(() => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'pepe (hat) es gesagt', answer: 'hat', index: 1 })
+                        .then(() => getExercises(user.id, activity.id)
+                            .then(result => {
+                                const { exercises, count } = result
+
+                                expect(exercises).to.be.an('array')
+                                expect(count).to.be.a('number')
+
+                                expect(exercises).to.have.lengthOf(2)
+
+                                expect(exercises[0].activity.toString()).to.equal(activity.id)
+                                expect(exercises[0].sentence).to.equal('alan (hat) es gegessen')
+                                expect(exercises[0].answer).to.equal('hat')
+                                expect(exercises[0].index).to.equal(0)
+
+                                expect(exercises[1].activity.toString()).to.equal(activity.id)
+                                expect(exercises[1].sentence).to.equal('pepe (hat) es gesagt')
+                                expect(exercises[1].answer).to.equal('hat')
+                                expect(exercises[1].index).to.equal(1)
+                            })))))
     })
 
     it('fails on non-existing user', () => {
@@ -55,13 +49,9 @@ describe('getExercises', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) =>
-                Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                    .then(() => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'pepe (hat) es gesagt', answer: 'hat', index: 1 }))
-                    .then(() => activity)
-            )
-            .then(activity => getExercises(new ObjectId().toString(), activity.id))
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(() => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'pepe (hat) es gesagt', answer: 'hat', index: 1 })
+                        .then(() => getExercises(new ObjectId().toString(), activity.id)))))
             .catch(error => errorThrown = error)
             .finally(() => {
                 expect(errorThrown).to.be.an.instanceOf(NotFoundError)
@@ -75,13 +65,9 @@ describe('getExercises', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mocha', surname: 'Chai', email: 'mocha@chai.es', username: 'mochachai', password: hash, userType: 'teacher' }))
             .then(user => Activity.create({ teacher: user.id, title: 'title', description: 'description' })
-                .then(activity => ({ user, activity })))
-            .then(({ user, activity }) =>
-                Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
-                    .then(() => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'pepe (hat) es gesagt', answer: 'hat', index: 1 }))
-                    .then(() => user)
-            )
-            .then(user => getExercises(user.id, new ObjectId().toString()))
+                .then(activity => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'alan (hat) es gegessen', answer: 'hat', index: 0 })
+                    .then(() => Exercise.create({ teacher: user.id, activity: activity.id, sentence: 'pepe (hat) es gesagt', answer: 'hat', index: 1 })
+                        .then(() => getExercises(user.id, new ObjectId().toString())))))
             .catch(error => errorThrown = error)
             .finally(() => {
                 expect(errorThrown).to.be.an.instanceOf(NotFoundError)
diff --git a/staff/agustin-birman/api/logic/user/addStudent.spec.js b/staff/agustin-birman/api/logic/user/addStudent.spec.js
index 89ab37619..b1f632c1c 100644
--- a/staff/agustin-birman/api/logic/user/addStudent.spec.js
+++ b/staff/agustin-birman/api/logic/user/addStudent.spec.js
@@ -21,16 +21,13 @@ describe('addStudent', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mac', surname: 'Book', email: 'mac@book.com', username: 'macbook', password: hash, userType: 'teacher' })
                 .then(user => User.create({ name: 'Wind', surname: 'Book', email: 'wind@book.com', username: 'windbook', password: hash, userType: 'teacher' })
-                    .then(student => ({ user, student }))))
-            .then(({ user, student }) => addStudent(user.id, student.id)
-                .then(() => User.findById(user.id))
-                .then(newUser => ({ newUser, student })))
-            .then(({ newUser, student }) => {
-                expect(newUser.student).to.include(student.id)
-            })
+                    .then(student => addStudent(user.id, student.id)
+                        .then(() => User.findById(user.id))
+                        .then(newUser => {
+                            expect(newUser.student).to.include(student.id)
+                        }))))
     })
 
-
     it('fails on non-existing user', () => {
         let errorThrown
 
@@ -63,11 +60,9 @@ describe('addStudent', () => {
         return bcrypt.hash('12345678', 8)
             .then(hash => User.create({ name: 'Mac', surname: 'Book', email: 'mac@book.com', username: 'macbook', password: hash, userType: 'teacher' })
                 .then(user => User.create({ name: 'Wind', surname: 'Book', email: 'wind@book.com', username: 'windbook', password: hash, userType: 'teacher' })
-                    .then(student => ({ user, student }))))
-            .then(({ user, student }) => addStudent(user.id, student.id)
-                .then(() => User.findById(user.id))
-                .then(user => ({ user, student })))
-            .then(({ user, student }) => addStudent(user.id, student.id))
+                    .then(student => addStudent(user.id, student.id)
+                        .then(() => User.findById(user.id)
+                            .then(() => addStudent(user.id, student.id))))))
             .catch(error => errorThrown = error)
             .finally(() => {
                 expect(errorThrown).to.be.an.instanceOf(DuplicityError)
diff --git a/staff/agustin-birman/api/logic/user/getStudents.spec.js b/staff/agustin-birman/api/logic/user/getStudents.spec.js
index 078f4c349..d5de60b24 100644
--- a/staff/agustin-birman/api/logic/user/getStudents.spec.js
+++ b/staff/agustin-birman/api/logic/user/getStudents.spec.js
@@ -47,18 +47,17 @@ describe('getStudents', () => {
             })]))
             .then(([teacher, student1, student2]) => addStudent(teacher.id, student1.id)
                 .then(() => addStudent(teacher.id, student2.id)
-                    .then(() => teacher)))
-            .then(teacher => User.findById(teacher.id))
-            .then(user => getStudents(user.id))
-            .then(listStudents => {
-                expect(listStudents).to.be.an('array')
-                expect(listStudents).to.have.lengthOf(2)
-
-                const usernames = listStudents.map(student => student.username)
-
-                expect(usernames).to.include('testuser')
-                expect(usernames).to.include('testuser2')
-            }))
+                    .then(() => User.findById(teacher.id)
+                        .then(user => getStudents(user.id))))
+                .then(listStudents => {
+                    expect(listStudents).to.be.an('array')
+                    expect(listStudents).to.have.lengthOf(2)
+
+                    const usernames = listStudents.map(student => student.username)
+
+                    expect(usernames).to.include('testuser')
+                    expect(usernames).to.include('testuser2')
+                })))
 
 
     it('fails on non-existing user', () => {
diff --git a/staff/agustin-birman/api/logic/user/getUserInfo.spec.js b/staff/agustin-birman/api/logic/user/getUserInfo.spec.js
new file mode 100644
index 000000000..5f2494cd3
--- /dev/null
+++ b/staff/agustin-birman/api/logic/user/getUserInfo.spec.js
@@ -0,0 +1,114 @@
+import 'dotenv/config'
+import mongoose, { Types } from 'mongoose'
+
+import bcrypt from 'bcryptjs'
+import getUserInfo from './getUserInfo.js'
+import { User } from '../../data/index.js'
+import { NotFoundError, ContentError } from 'com/errors.js'
+
+import { expect } from 'chai'
+
+const { MONGODB_URL_TEST } = process.env
+
+const { ObjectId } = Types
+
+
+describe('getUserInfo', () => {
+    before(() => mongoose.connect(MONGODB_URL_TEST).then(() => User.deleteMany()))
+
+    beforeEach(() => User.deleteMany())
+
+    it('succeeds get userName from existing user', () =>
+        bcrypt.hash('1234', 8)
+            .then(hash => Promise.all([User.create({
+                name: 'Mocha',
+                surname: 'Chai',
+                email: 'Mocha@Chai.com',
+                username: 'MochaChai',
+                password: hash,
+                userType: 'teacher'
+            }), User.create({
+                name: 'Test',
+                surname: 'User',
+                email: 'test@user.com',
+                username: 'testuser',
+                password: hash,
+                userType: 'teacher'
+            })]))
+            .then(([user, targetUser]) => getUserInfo(user.id, targetUser.id)
+                .then(userInfo => {
+                    expect(userInfo).to.have.property('name').that.equals('Test');
+                    expect(userInfo).to.have.property('surname').that.equals('User');
+                    expect(userInfo).to.have.property('email').that.equals('test@user.com');
+                    expect(userInfo).to.have.property('username').that.equals('testuser');
+                })
+            ))
+
+    it('fails on non-existing user', () => {
+        let errorThrown
+        return bcrypt.hash('12345678', 8)
+            .then(hash => User.create({
+                name: 'Test',
+                surname: 'User',
+                email: 'test@user.com',
+                username: 'testuser',
+                password: hash,
+                userType: 'teacher'
+            })
+                .then(userInfo => getUserInfo(new ObjectId().toString(), userInfo.id)))
+            .catch(error => errorThrown = error)
+            .finally(() => {
+                expect(errorThrown).to.be.an.instanceOf(NotFoundError)
+                expect(errorThrown.message).to.equal('user not found')
+            })
+    })
+
+    it('fails on non-existing targetUser', () => {
+        let errorThrown
+        return bcrypt.hash('12345678', 8)
+            .then(hash => User.create({
+                name: 'Test',
+                surname: 'User',
+                email: 'test@user.com',
+                username: 'testuser',
+                password: hash,
+                userType: 'teacher'
+            })
+                .then(user => getUserInfo(user.id, new ObjectId().toString())))
+            .catch(error => errorThrown = error)
+            .finally(() => {
+                expect(errorThrown).to.be.an.instanceOf(NotFoundError)
+                expect(errorThrown.message).to.equal('userInfo not found')
+            })
+    })
+
+    it('fails on invalid userId', () => {
+        let errorThrown
+
+        try {
+            getUserInfo(12345, new ObjectId().toString())
+        } catch (error) {
+            errorThrown = error
+
+        } finally {
+            expect(errorThrown).to.be.instanceOf(ContentError)
+            expect(errorThrown.message).to.equal('userId is not valid')
+        }
+    })
+
+    it('fails on invalid userInfo', () => {
+        let errorThrown
+
+        try {
+            getUserInfo(new ObjectId().toString(), 12345)
+        } catch (error) {
+            errorThrown = error
+
+        } finally {
+            expect(errorThrown).to.be.instanceOf(ContentError)
+            expect(errorThrown.message).to.equal('userInfoId is not valid')
+        }
+    })
+
+    after(() => User.deleteMany().then(() => mongoose.disconnect()))
+})
\ No newline at end of file
diff --git a/staff/agustin-birman/api/logic/user/registerUser.spec.js b/staff/agustin-birman/api/logic/user/registerUser.spec.js
index e95f435af..c22ae1c68 100644
--- a/staff/agustin-birman/api/logic/user/registerUser.spec.js
+++ b/staff/agustin-birman/api/logic/user/registerUser.spec.js
@@ -117,6 +117,18 @@ describe('registerUser', () => {
         }
     })
 
+    it('fails on invalid userType', () => {
+        let errorThrown
+        try {
+            registerUser('Mocha', 'Chai', 'Mocha@Chai.com', 'MochaChai', '12345678', '12345678', 12345678)
+        } catch (error) {
+            errorThrown = error
+        } finally {
+            expect(errorThrown).to.be.instanceOf(ContentError)
+            expect(errorThrown.message).to.equal('userType is not valid')
+        }
+    })
+
 
 
     after(() => User.deleteMany().then(() => mongoose.disconnect()))
diff --git a/staff/agustin-birman/api/logic/user/removeStudent.spec.js b/staff/agustin-birman/api/logic/user/removeStudent.spec.js
new file mode 100644
index 000000000..86b3595a0
--- /dev/null
+++ b/staff/agustin-birman/api/logic/user/removeStudent.spec.js
@@ -0,0 +1,115 @@
+import 'dotenv/config'
+import mongoose, { Types } from 'mongoose'
+import { expect } from 'chai'
+import bcrypt from 'bcryptjs'
+
+import { User } from '../../data/index.js'
+import removeStudent from './removeStudent.js'
+import { ContentError, NotFoundError } from 'com/errors.js'
+
+const { MONGODB_URL_TEST } = process.env
+const { ObjectId } = Types
+
+describe('removeStudent', () => {
+    before(() => mongoose.connect(MONGODB_URL_TEST))
+
+    beforeEach(() => User.deleteMany())
+
+    it('succeeds on removing student', () =>
+        bcrypt.hash('12345678', 8)
+            .then(hash => User.create({
+                name: 'Test',
+                surname: 'User',
+                email: 'test@user.com',
+                username: 'testuser',
+                password: hash,
+                userType: 'teacher'
+            })
+                .then(studentInfo => User.create({
+                    name: 'Mocha',
+                    surname: 'Chai',
+                    email: 'Mocha@Chai.com',
+                    username: 'MochaChai',
+                    password: hash,
+                    userType: 'teacher',
+                    student: studentInfo.id
+                })
+                    .then(teacher => removeStudent(teacher.id, studentInfo.id)
+                        .then(() => User.findById(teacher.id)))))
+            .then(teacherInfo => {
+                expect(teacherInfo.student).to.be.an('array')
+                expect(teacherInfo.student).to.have.lengthOf(0)
+            })
+    )
+
+    it('fails on non-existing teacher', () => {
+
+        bcrypt.hash('12345678', 8)
+            .then(hash => User.create({
+                name: 'Test',
+                surname: 'User',
+                email: 'test@user.com',
+                username: 'testuser',
+                password: hash,
+                userType: 'teacher'
+            })
+                .then(studentInfo => removeStudent(new ObjectId().toString(), studentInfo.id)
+                    .then(() => User.findById(teacher.id))))
+            .catch(error => errorThrown = error)
+            .finally(() => {
+                expect(errorThrown).to.be.an.instanceOf(NotFoundError)
+                expect(errorThrown.message).to.equal('user not found')
+            })
+    })
+
+    it('fails on non-existing student', () => {
+
+        bcrypt.hash('12345678', 8)
+            .then(hash => User.create({
+                name: 'Test',
+                surname: 'User',
+                email: 'test@user.com',
+                username: 'testuser',
+                password: hash,
+                userType: 'teacher'
+            })
+                .then(teacher => removeStudent(teacher.id, new ObjectId().toString())
+                    .then(() => User.findById(teacher.id))))
+            .catch(error => errorThrown = error)
+            .finally(() => {
+                expect(errorThrown).to.be.an.instanceOf(NotFoundError)
+                expect(errorThrown.message).to.equal('student is not in your list')
+            })
+    })
+
+    it('fails on invalid userId', () => {
+        let errorThrown
+
+        try {
+            removeStudent(12345, new ObjectId().toString())
+        } catch (error) {
+            errorThrown = error
+
+        } finally {
+            expect(errorThrown).to.be.instanceOf(ContentError)
+            expect(errorThrown.message).to.equal('userId is not valid')
+        }
+    })
+
+    it('fails on invalid studentId', () => {
+        let errorThrown
+
+        try {
+            removeStudent(new ObjectId().toString(), 12345)
+        } catch (error) {
+            errorThrown = error
+
+        } finally {
+            expect(errorThrown).to.be.instanceOf(ContentError)
+            expect(errorThrown.message).to.equal('studentId is not valid')
+        }
+    })
+
+
+    after(() => User.deleteMany().then(() => mongoose.disconnect()))
+})
\ No newline at end of file
diff --git a/staff/agustin-birman/app/src/App.jsx b/staff/agustin-birman/app/src/App.jsx
index 3b3c9c62f..81bc11613 100644
--- a/staff/agustin-birman/app/src/App.jsx
+++ b/staff/agustin-birman/app/src/App.jsx
@@ -4,6 +4,7 @@ import Register from './views/Register'
 import Login from './views/Login'
 import Home from './views/Home'
 import logic from './logic'
+import './global.css'
 
 function App() {
     console.log('App -> render')
diff --git a/staff/agustin-birman/app/src/components/core/Button/index.css b/staff/agustin-birman/app/src/components/core/Button/index.css
index 9fc39466d..6c646479d 100644
--- a/staff/agustin-birman/app/src/components/core/Button/index.css
+++ b/staff/agustin-birman/app/src/components/core/Button/index.css
@@ -19,11 +19,3 @@
     padding: 0.3rem;
 } 
 
-.hola{
-    width: 90%;
-    height: 15%;
-    padding: 10px;
-    border: 1px solid black;
-    border-radius: 20px;
-    margin-bottom: 1rem;
-}
\ No newline at end of file
diff --git a/staff/agustin-birman/app/src/components/core/SubmitButton/index.css b/staff/agustin-birman/app/src/components/core/SubmitButton/index.css
index d1abcb0ea..e69de29bb 100644
--- a/staff/agustin-birman/app/src/components/core/SubmitButton/index.css
+++ b/staff/agustin-birman/app/src/components/core/SubmitButton/index.css
@@ -1,3 +0,0 @@
-.Image {
-    width: 100%;
-}
\ No newline at end of file
diff --git a/staff/agustin-birman/app/src/components/core/SubmitButton/index.jsx b/staff/agustin-birman/app/src/components/core/SubmitButton/index.jsx
index 663e65019..d0eb7e7d5 100644
--- a/staff/agustin-birman/app/src/components/core/SubmitButton/index.jsx
+++ b/staff/agustin-birman/app/src/components/core/SubmitButton/index.jsx
@@ -1,6 +1,5 @@
 import Button from '../Button'
 
-import './index.css'
 
 function SubmitButton({ children }) {
     return <Button className='SubmitButton' type='submit'>{children}</Button>
diff --git a/staff/agustin-birman/app/src/components/core/Text/index.css b/staff/agustin-birman/app/src/components/core/Text/index.css
index d1abcb0ea..e69de29bb 100644
--- a/staff/agustin-birman/app/src/components/core/Text/index.css
+++ b/staff/agustin-birman/app/src/components/core/Text/index.css
@@ -1,3 +0,0 @@
-.Image {
-    width: 100%;
-}
\ No newline at end of file
diff --git a/staff/agustin-birman/app/src/components/library/Exercises/index.jsx b/staff/agustin-birman/app/src/components/library/Exercises/index.jsx
new file mode 100644
index 000000000..401a74702
--- /dev/null
+++ b/staff/agustin-birman/app/src/components/library/Exercises/index.jsx
@@ -0,0 +1,68 @@
+import { useEffect, useState } from "react"
+import View from "../View"
+import Heading from "../../core/Heading"
+import Text from "../../core/Text"
+import Button from "../../core/Button"
+import logic from "../../../logic"
+
+function Exercises({ activityId, onEditButton, updateExercises }) {
+    const [exercises, setExercises] = useState([])
+
+    useEffect(() =>
+        loadExercises()
+        , [updateExercises])
+
+    const loadExercises = () => {
+        try {
+            logic.getExercises(activityId)
+                .then(data => {
+                    const { exercises } = data
+                    setExercises(exercises)
+                })
+                .catch(error => {
+                    console.error(error)
+
+                    alert(error.message) //TODO hacer un alert mejor
+                })
+        } catch (error) {
+            console.error(error)
+
+            alert(error.message)
+        }
+    }
+
+    const handleDeletedExericise = (exerciseId) => {
+        try {
+            logic.deleteExercise(exerciseId)
+                .then(() => loadExercises())
+                .catch(error => {
+                    console.error(error)
+
+                    alert(error.message)
+                })
+        } catch (error) {
+            console.error(error)
+
+            alert(error.message)
+        }
+    }
+
+    return <View className='ListExercise'>
+        <Heading level='2'>List Exercises</Heading>
+        {exercises.map(exercise =>
+            <View className='Exercise' key={exercise.id}>
+                <View className='ExerciseText'>
+                    <Text>{exercise.index + 1}</Text>
+                    <Text>{exercise.sentence}</Text>
+                    <Text>{exercise.answer}</Text>
+                </View>
+                <View className='ExerciseButtons'>
+                    <Button onClick={() => onEditButton(exercise)}>Edit</Button>
+                    <Button onClick={() => handleDeletedExericise(exercise.id)}>Delete</Button>
+                </View>
+            </View>
+        )}
+    </View>
+}
+
+export default Exercises
\ No newline at end of file
diff --git a/staff/agustin-birman/app/src/components/library/MenuItem/index.css b/staff/agustin-birman/app/src/components/library/MenuItem/index.css
index be7b5f87a..e69de29bb 100644
--- a/staff/agustin-birman/app/src/components/library/MenuItem/index.css
+++ b/staff/agustin-birman/app/src/components/library/MenuItem/index.css
@@ -1,7 +0,0 @@
-/* .menuItem {
-        width: 90%;
-        margin-top: 10%;
-        height: 15%;
-        border: 1px solid black;
-        border-radius: 10px;
-} */
\ No newline at end of file
diff --git a/staff/agustin-birman/app/src/global.css b/staff/agustin-birman/app/src/global.css
index acd510241..71af91d0b 100644
--- a/staff/agustin-birman/app/src/global.css
+++ b/staff/agustin-birman/app/src/global.css
@@ -19,3 +19,5 @@
     }
     
 }
+
+
diff --git a/staff/agustin-birman/app/src/main.jsx b/staff/agustin-birman/app/src/main.jsx
index a130dbca3..b286afd19 100644
--- a/staff/agustin-birman/app/src/main.jsx
+++ b/staff/agustin-birman/app/src/main.jsx
@@ -4,6 +4,7 @@ import App from './App.jsx'
 import { BrowserRouter as Router } from 'react-router-dom'
 
 
+
 ReactDOM.createRoot(document.getElementById('root')).render(
   // <React.StrictMode>
   <Router>
diff --git a/staff/agustin-birman/app/src/views/Login.css b/staff/agustin-birman/app/src/views/Login.css
index 52ca26366..dfae11b4b 100644
--- a/staff/agustin-birman/app/src/views/Login.css
+++ b/staff/agustin-birman/app/src/views/Login.css
@@ -9,12 +9,13 @@ main {
     height: 100%;
 }
 
-h1 {
+h1{
     margin-top: 10%;
     font-size: 2rem ;
     font-weight: bold;
 }
 
+
 .LoginForm {
     margin-top: 20%;
     padding: 1rem;
diff --git a/staff/agustin-birman/app/src/views/Login.jsx b/staff/agustin-birman/app/src/views/Login.jsx
index bdae639fa..62b1d3249 100644
--- a/staff/agustin-birman/app/src/views/Login.jsx
+++ b/staff/agustin-birman/app/src/views/Login.jsx
@@ -1,7 +1,6 @@
 import { useState } from 'react'
 import logic from '../logic'
 
-import '../global.css'
 import './Login.css'
 
 import Field from '../components/core/Field'
diff --git a/staff/agustin-birman/app/src/views/Register.jsx b/staff/agustin-birman/app/src/views/Register.jsx
index a3343dd61..b0035550d 100644
--- a/staff/agustin-birman/app/src/views/Register.jsx
+++ b/staff/agustin-birman/app/src/views/Register.jsx
@@ -1,4 +1,3 @@
-import '../global.css'
 import logic from '../logic'
 
 import './Register.css'
diff --git a/staff/agustin-birman/app/src/views/components/AddStudent/index.jsx b/staff/agustin-birman/app/src/views/components/AddStudent/index.jsx
index 3fa90dae9..80df04d45 100644
--- a/staff/agustin-birman/app/src/views/components/AddStudent/index.jsx
+++ b/staff/agustin-birman/app/src/views/components/AddStudent/index.jsx
@@ -2,13 +2,14 @@ import logic from '../../../logic'
 import View from '../../../components/library/View'
 import Heading from '../../../components/core/Heading'
 import Text from '../../../components/core/Text'
-import { useParams } from 'react-router-dom'
+import { useNavigate, useParams } from 'react-router-dom'
 import { useEffect, useState } from 'react'
 import Button from '../../../components/core/Button'
 
 function AddStudent() {
     const [userInfo, setUserInfo] = useState('')
     const { userInfoId } = useParams()
+    const navigate = useNavigate()
 
     useEffect(() => {
         getUserInfo()
@@ -33,7 +34,7 @@ function AddStudent() {
     const handleAddStudent = () => {
         try {
             logic.addStudent(userInfoId)
-                .then(user => setUserInfo(user))
+                .then(() => navigate('/users/students'))
                 .catch(error => {
                     console.error(error)
 
diff --git a/staff/agustin-birman/app/src/views/components/CompleteSentence/index.jsx b/staff/agustin-birman/app/src/views/components/CompleteSentence/index.jsx
index 49b2dbc41..add06d77d 100644
--- a/staff/agustin-birman/app/src/views/components/CompleteSentence/index.jsx
+++ b/staff/agustin-birman/app/src/views/components/CompleteSentence/index.jsx
@@ -12,23 +12,20 @@ import Input from '../../../components/core/Input'
 
 import logic from '../../../logic'
 import View from '../../../components/library/View'
+import Exercises from '../../../components/library/Exercises'
 
 const ANSWER_REGEX = /\(([^)]+)\)/
 
 function CreateCompleteSentence() {
     const [message, setMessage] = useState('')
     const [answerInput, setAnswerInput] = useState('Not answer found')
-    const [exercises, setExercises] = useState([])
     const [editView, setEditView] = useState(false)
     const [sentence, setSentence] = useState('')
     const [selectedExercise, setSelectedExercise] = useState(null)
+    const [updateExercises, setUpdateExercises] = useState(0)
 
     const { activityId } = useParams()
 
-    useEffect(() =>
-        loadExercises()
-        , [])
-
     useEffect(() => {
         if (sentence) {
             const removeAnswer = sentence.match(ANSWER_REGEX)
@@ -41,46 +38,11 @@ function CreateCompleteSentence() {
     }
         , [editView])
 
-    const loadExercises = () => {
-        try {
-            logic.getExercises(activityId)
-                .then(data => {
-                    const { exercises } = data
-                    setExercises(exercises)
-                })
-                .catch(error => {
-                    console.error(error)
-
-                    alert(error.message) //TODO hacer un alert mejor
-                })
-        } catch (error) {
-            console.error(error)
-
-            alert(error.message)
-        }
-    }
-
-    const handleDeletedExericise = (exerciseId) => {
-        try {
-            logic.deleteExercise(exerciseId)
-                .then(() => loadExercises())
-                .catch(error => {
-                    console.error(error)
-
-                    alert(error.message)
-                })
-        } catch (error) {
-            console.error(error)
-
-            alert(error.message)
-        }
-    }
-
     const handleEditedExercise = () => {
         try {
-            logic.editExercise(selectedExercise._id, sentence)
+            logic.editExercise(selectedExercise.id, sentence)
                 .then(() => {
-                    loadExercises()
+                    setUpdateExercises(prev => prev + 1)
                     setEditView(false)
                 })
                 .catch(error => {
@@ -105,7 +67,7 @@ function CreateCompleteSentence() {
                 .then(() => {
                     form.reset()
                     setAnswerInput('Answer not found')
-                    loadExercises()
+                    setUpdateExercises(prev => prev + 1)
                 })
                 .catch(error => {
                     console.error(error)
@@ -142,9 +104,10 @@ function CreateCompleteSentence() {
             <Heading level='2'>-Complete the sentence</Heading>
 
             {editView === false
-                ? <Field id='sentence' placeholder='Alex (hat) es gegessen' onChange={handleAnswerInput}>{(exercises && exercises.length > 0 && exercises[exercises.length - 1].index !== undefined)
-                    ? exercises[exercises.length - 1].index + 2
-                    : 1}. Sentence</Field>
+                // ? <Field id='sentence' placeholder='Alex (hat) es gegessen' onChange={handleAnswerInput}>{(exercises && exercises.length > 0 && exercises[exercises.length - 1].index !== undefined)
+                //     ? exercises[exercises.length - 1].index + 2
+                //     : 1}. Sentence</Field>
+                ? <Field id='sentence' placeholder='Alex (hat) es gegessen' onChange={handleAnswerInput}>Sentence</Field>
                 : <><Text>{selectedExercise.index + 1}. Sentence</Text>
                     <Input value={sentence} onChange={(e) => { setSentence(e.target.value); handleAnswerInput(e) }} /></>}
             <Heading level='3'>-Answer</Heading>
@@ -166,24 +129,7 @@ function CreateCompleteSentence() {
                 </>}
         </FormWithFeedback>
 
-        {editView === false && <>
-            <Heading level='2'>List Exercises</Heading>
-            <View className='ListExercise'>
-                {exercises.map(exercise =>
-                    //TODO modificar el id
-                    <View className='Exercise' key={exercise._id}>
-                        <View className='ExerciseText'>
-                            <Text>{exercise.index + 1}</Text>
-                            <Text>{exercise.sentence}</Text>
-                            <Text>{exercise.answer}</Text>
-                        </View>
-                        <View className='ExerciseButtons'>
-                            <Button onClick={() => handleEditButton(exercise)}>Edit</Button>
-                            <Button onClick={() => handleDeletedExericise(exercise._id)}>Delete</Button>
-                        </View>
-                    </View>
-                )}
-            </View>
+        {editView === false && <> <Exercises activityId={activityId} onEditButton={handleEditButton} updateExercises={updateExercises} />
         </>}
     </View>
 
diff --git a/staff/agustin-birman/app/src/views/components/CompleteSentenceInfo/index.css b/staff/agustin-birman/app/src/views/components/CompleteSentenceInfo/index.css
index b804d15a4..e69de29bb 100644
--- a/staff/agustin-birman/app/src/views/components/CompleteSentenceInfo/index.css
+++ b/staff/agustin-birman/app/src/views/components/CompleteSentenceInfo/index.css
@@ -1,3 +0,0 @@
-.Text{
-    width: 90%;
-}
\ No newline at end of file
diff --git a/staff/agustin-birman/app/src/views/components/DoActivity/index.jsx b/staff/agustin-birman/app/src/views/components/DoActivity/index.jsx
index 555b8feff..3d6176546 100644
--- a/staff/agustin-birman/app/src/views/components/DoActivity/index.jsx
+++ b/staff/agustin-birman/app/src/views/components/DoActivity/index.jsx
@@ -106,8 +106,8 @@ function DoActivity() {
                 </div>
 
                 {isLastPage === false
-                    ? <Button onClick={() => handleSubmittedAnswer(exercise._id)}>Next Exercise</Button>
-                    : <Button onClick={() => handleSubmittedAnswer(exercise._id)}>Finish</Button>}
+                    ? <Button onClick={() => handleSubmittedAnswer(exercise.id)}>Next Exercise</Button>
+                    : <Button onClick={() => handleSubmittedAnswer(exercise.id)}>Finish</Button>}
                 <Text>{message}</Text>
 
                 <Text>Page {currentPage} of {Math.ceil(exercises.length / pageSize)}</Text>
diff --git a/staff/agustin-birman/app/src/views/components/ListActivities/index.jsx b/staff/agustin-birman/app/src/views/components/ListActivities/index.jsx
index 3930e8332..f837b8d49 100644
--- a/staff/agustin-birman/app/src/views/components/ListActivities/index.jsx
+++ b/staff/agustin-birman/app/src/views/components/ListActivities/index.jsx
@@ -35,9 +35,8 @@ function ListActivities() {
         <Heading level='2'>Activities List</Heading>
         <div className='ActivitiesList'>
             {activities.map(activity =>
-                //TODO modificar el id
-                <div className='Activity' key={activity._id}>
-                    <Link to={`/activities/${activity._id}`}>
+                <div className='Activity' key={activity.id}>
+                    <Link to={`/activities/${activity.id}`}>
                         <Text>kind activity</Text>
                         <Text>{activity.title}</Text>
                     </Link>
diff --git a/staff/agustin-birman/app/src/views/components/ListExercises/index.jsx b/staff/agustin-birman/app/src/views/components/ListExercises/index.jsx
index 9fbd14ed7..84872d147 100644
--- a/staff/agustin-birman/app/src/views/components/ListExercises/index.jsx
+++ b/staff/agustin-birman/app/src/views/components/ListExercises/index.jsx
@@ -36,28 +36,12 @@ function ListExercises() {
         }
     }
 
-    const handleExerciseDeleted = (exerciseId) => {
-        try {
-            logic.deleteExercise(exerciseId)
-                .then(() => { loadExercises() })
-                .catch(error => {
-                    console.error(error)
-
-                    alert(error.message)
-                })
-        } catch (error) {
-            console.error(error)
-
-            alert(error.message)
-        }
-    }
-
     return <View>
         <Heading level='2'>Exercises List</Heading>
         <View className='ActivitiesList'>
             {exercises.map(exercise =>
                 //TODO modificar el id
-                <View className='Exercise' key={exercise._id}>
+                <View className='Exercise' key={exercise.id}>
                     <View className='ExerciseText'>
                         <Text>{exercise.index + 1}</Text>
                         <Text>{exercise.sentence}</Text>
diff --git a/staff/agustin-birman/app/src/views/components/ListStudents/index.jsx b/staff/agustin-birman/app/src/views/components/ListStudents/index.jsx
index 77a14ced3..f2139bdee 100644
--- a/staff/agustin-birman/app/src/views/components/ListStudents/index.jsx
+++ b/staff/agustin-birman/app/src/views/components/ListStudents/index.jsx
@@ -49,17 +49,16 @@ function ListStudents() {
     }
 
 
-    console.log(students)
     return <View>
         <Heading level='2'>Students List</Heading>
         <View className='ActivitiesList'>
             {students.map(student =>
                 //TODO modificar el id
-                <View className='Exercise' key={student._id}>
+                <View className='Exercise' key={student.id}>
                     <View className='ExerciseText'>
                         <Text>{student.name}</Text>
                         <Text>{student.surname}</Text>
-                        <Button onClick={() => handleDeleteStudent(student._id)}>Delete Student</Button>
+                        <Button onClick={() => handleDeleteStudent(student.id)}>Delete Student</Button>
 
                     </View>
 
diff --git a/staff/agustin-birman/app/src/views/components/MenuItems/index.css b/staff/agustin-birman/app/src/views/components/MenuItems/index.css
index e69de29bb..5e8294737 100644
--- a/staff/agustin-birman/app/src/views/components/MenuItems/index.css
+++ b/staff/agustin-birman/app/src/views/components/MenuItems/index.css
@@ -0,0 +1,8 @@
+.MenuItem{
+    width: 90%;
+    height: 15%;
+    padding: 10px;
+    border: 1px solid black;
+    border-radius: 20px;
+    margin-bottom: 1rem;
+}
\ No newline at end of file
diff --git a/staff/agustin-birman/app/src/views/components/MenuItems/index.jsx b/staff/agustin-birman/app/src/views/components/MenuItems/index.jsx
index dd0f93b35..ec677910d 100644
--- a/staff/agustin-birman/app/src/views/components/MenuItems/index.jsx
+++ b/staff/agustin-birman/app/src/views/components/MenuItems/index.jsx
@@ -1,16 +1,17 @@
 import Button from '../../../components/core/Button'
 import View from '../../../components/library/View'
 import { Link } from 'react-router-dom'
+import './index.css'
 import extractPayloadFromJWT from '../../../utils/extractPayloadFromJWT'
 
 function MenuItem() {
     const { sub: userId } = extractPayloadFromJWT(localStorage.token)
 
     return <View tag='main'>
-        <Button className='hola'><Link to='/activities/select-type'>Create a activity</Link></Button>
-        <Button className='hola'><Link to='/activities/list'>View activities</Link></Button>
-        <Button className='hola'><Link to='/users/students'>View students</Link></Button>
-        <Button className='hola'><Link to={`/users/${userId}`}>Share ID</Link></Button>
+        <Button className='MenuItem'><Link to='/activities/select-type'>Create a activity</Link></Button>
+        <Button className='MenuItem'><Link to='/activities/list'>View activities</Link></Button>
+        <Button className='MenuItem'><Link to='/users/students'>View students</Link></Button>
+        <Button className='MenuItem'><Link to={`/users/${userId}`}>Share ID</Link></Button>
 
     </View >
 
diff --git a/staff/agustin-birman/app/src/views/components/ShowExerciseResults/index.jsx b/staff/agustin-birman/app/src/views/components/ShowExerciseResults/index.jsx
index 384307701..f64c53235 100644
--- a/staff/agustin-birman/app/src/views/components/ShowExerciseResults/index.jsx
+++ b/staff/agustin-birman/app/src/views/components/ShowExerciseResults/index.jsx
@@ -23,7 +23,7 @@ function ShowExerciseResults() {
                 .then(data => {
                     const { exercises } = data
                     const promises = exercises.map(exercise =>
-                        logic.getAnswers(exercise._id)
+                        logic.getAnswers(exercise.id)
                             .then(answers => ({
                                 ...exercise,
                                 answers
@@ -57,7 +57,7 @@ function ShowExerciseResults() {
         <View>
             <Heading level='2'>Results</Heading>
             {exercisesWithAnswers.map(exercise => (
-                <View className='Exercise' key={exercise._id}>
+                <View className='Exercise' key={exercise.id}>
                     <View className='ExerciseText'>
                         <Text>{exercise.index + 1}</Text>
                         <Text>{exercise.sentence}</Text>