diff --git a/test/tests/util/awayKey.js b/test/tests/util/awayKey.js
new file mode 100644
index 00000000..ccd82121
--- /dev/null
+++ b/test/tests/util/awayKey.js
@@ -0,0 +1,28 @@
+/* @flow */
+
+import { awaitKey } from '../../../src';
+
+describe('awaitKey cases', () => {
+    it('awaitKey should return the value when existing', () => {
+        const obj = {
+            custom: true
+        };
+        const result = awaitKey(obj, 'custom');
+
+        if (!result) {
+            throw new Error(`should return "true", but got: ${ result }`);
+        }
+    });
+
+    it('awaitKey should return the configured value when does not exists', () => {
+        const obj = {};
+
+        awaitKey(obj, 'custom');
+        obj.custom = 'result';
+        const result = obj.custom;
+
+        if (result !== 'result') {
+            throw new Error(`should return "result", but got: ${ result }`);
+        }
+    });
+});
diff --git a/test/tests/util/extend.js b/test/tests/util/extend.js
index 28036e02..9e84e88e 100644
--- a/test/tests/util/extend.js
+++ b/test/tests/util/extend.js
@@ -4,6 +4,15 @@ import { extend } from '../../../src';
 
 describe('extend cases', () => {
 
+    it('should return same object when second argument is empty', () => {
+        const result = extend({ a: true });
+        const arrayResult = Object.entries(result).flat();
+
+        if (arrayResult[0] !== 'a' || !arrayResult[1]) {
+            throw new Error(`should return the exact same first argument object, but got: ${ String(result) }`);
+        }
+    });
+
     it('should add keys from one object to another', () => {
         const obj1 : Object = {
             'foo': 1,
@@ -31,4 +40,17 @@ describe('extend cases', () => {
             throw new Error(`Expected obj1.bloop to equal 6, got ${ obj1.bloop }`);
         }
     });
+
+    it('should return the extend object when Object.assign is not valid', () => {
+        const originalFunc = Object.assign;
+        Reflect.deleteProperty(Object, 'assign');
+        const result = extend({ a: true }, { b: false });
+        const arrayResult = Object.entries(result).flat();
+
+        if (arrayResult[0] !== 'a' || !arrayResult[1] ||
+            arrayResult[2] !== 'b' || arrayResult[3]) {
+            throw new Error(`should return the extended object, but got: ${ String(result) }`);
+        }
+        Reflect.defineProperty(Object, 'assign', originalFunc);
+    });
 });
diff --git a/test/tests/util/index.js b/test/tests/util/index.js
index db9658a8..1b0ddc87 100644
--- a/test/tests/util/index.js
+++ b/test/tests/util/index.js
@@ -7,7 +7,13 @@ import './extend';
 import './serialize';
 import './domainMatches';
 import './identity';
+import './stringify';
+import './stringifyError';
 import './stringifyErrorMessage';
 import './isRegex';
 import './isDefined';
 import './base64encode';
+import './patch';
+import './match';
+import './awayKey';
+import './values';
diff --git a/test/tests/util/match.js b/test/tests/util/match.js
new file mode 100644
index 00000000..4aeaa8fb
--- /dev/null
+++ b/test/tests/util/match.js
@@ -0,0 +1,13 @@
+/* @flow */
+
+import { match } from '../../../src';
+
+describe('match cases', () => {
+    it('match should return original function', () => {
+        const result = match('letters', /(t[a-z]*)/i);
+
+        if (result !== 'tters') {
+            throw new Error(`should return "tters", but got: ${ String(result) }`);
+        }
+    });
+});
diff --git a/test/tests/util/patch.js b/test/tests/util/patch.js
new file mode 100644
index 00000000..a07ec47e
--- /dev/null
+++ b/test/tests/util/patch.js
@@ -0,0 +1,23 @@
+/* @flow */
+
+import { patchMethod } from '../../../src';
+
+describe('patchMethod cases', () => {
+    it('patchMethod should return original function', () => {
+        const obj = {
+            custom() : string {
+                return 'first';
+            }
+        };
+        const handler = ({ callOriginal }) => {
+            return callOriginal();
+        };
+
+        patchMethod(obj, 'custom', handler);
+        const result = obj.custom();
+
+        if (result !== 'first') {
+            throw new Error(`should return "first", but got: ${ result }`);
+        }
+    });
+});
diff --git a/test/tests/util/stringify.js b/test/tests/util/stringify.js
new file mode 100644
index 00000000..d3b09a8f
--- /dev/null
+++ b/test/tests/util/stringify.js
@@ -0,0 +1,13 @@
+/* @flow */
+
+import {  stringify } from '../../../src';
+
+describe('stringify cases', () => {
+    it('stringify should return the exact same value when is a string value', () => {
+        const result = stringify('1');
+
+        if (result !== '1') {
+            throw new Error(`should return value "1", but got: ${ result }`);
+        }
+    });
+});
diff --git a/test/tests/util/stringifyError.js b/test/tests/util/stringifyError.js
new file mode 100644
index 00000000..53f3dfd8
--- /dev/null
+++ b/test/tests/util/stringifyError.js
@@ -0,0 +1,108 @@
+/* @flow */
+
+import { stringifyError } from '../../../src';
+
+describe('stringifyError cases', () => {
+    it('stringifyError should return stack overflow error message', () => {
+        const expectedResult = 'stringifyError stack overflow';
+        const result = stringifyError('custom error', 4);
+
+        if (result !== expectedResult) {
+            throw new Error(`should throw the error message "${ expectedResult }", but got: ${ result }`);
+        }
+    });
+
+    it('stringifyError should return unknown error message', () => {
+        const expectedResult = `<unknown error: [object Number]>`;
+        const result = stringifyError(0, 1);
+
+        if (result !== expectedResult) {
+            throw new Error(`should throw the error messagee "${ expectedResult }", but got: ${ result }`);
+        }
+    });
+
+    it('stringifyError should return the exact same error message when is a string type', () => {
+        const expectedResult = `my error`;
+        const result = stringifyError(expectedResult, 1);
+
+        if (result !== expectedResult) {
+            throw new Error(`should throw the error message "${ expectedResult }", but got: ${ result }`);
+        }
+    });
+
+    it('stringifyError should return only the stack when is an Error instance', () => {
+        const expectedResult = `custom`;
+        const error = new Error(expectedResult);
+        const result = stringifyError(error, 1);
+
+        if (!result.startsWith(`Error: ${ expectedResult }`)) {
+            throw new Error(`should throw the error message starting with "Error: ${ expectedResult }", but got: ${ result }`);
+        }
+    });
+
+    it('stringifyError should return the only the stack when is an Error instance with empty message', () => {
+        const expectedResult = `at Context.<anonymous>`;
+        const error = new Error('anything not important');
+
+        error.message = '';
+        const result = stringifyError(error, 1);
+
+        if (!result.includes(expectedResult)) {
+            throw new Error(`should throw the error message starting with "${ expectedResult }", but got: ${ result }`);
+        }
+    });
+
+    it('stringifyError should return the only the message when is an Error instance with empty stack', () => {
+        const expectedResult = `error instance`;
+        const error = new Error(expectedResult);
+
+        error.stack = '';
+        const result = stringifyError(error, 1);
+
+        if (result !== expectedResult) {
+            throw new Error(`should throw the error message "${ expectedResult }", but got: ${ result }`);
+        }
+    });
+
+    it('stringifyError should return the message and stack when is and Error instance and message is not include in the stack', () => {
+        const expectedErrorMessage = 'Error: custom at line whatever';
+        const error = new Error('custom');
+
+        error.message = 'message';
+        error.stack = expectedErrorMessage;
+        const result = stringifyError(error, 1);
+
+        if (!result.endsWith(expectedErrorMessage)) {
+            throw new Error(`should throw the error message ending with "${ expectedErrorMessage }", but got: ${ result }`);
+        }
+    });
+
+    it('stringifyError should return call toString when error message is an object', () => {
+        const expectedErrorMessage = '[object Object]';
+        const result = stringifyError({}, 1);
+
+        if (result !== expectedErrorMessage) {
+            throw new Error(`should throw the error message "${ expectedErrorMessage }", but got: ${ result }`);
+        }
+    });
+
+    it('stringifyError should return call toString from Object.prototype when error message is object', () => {
+        const expectedErrorMessage = '[object Object]';
+        const result = stringifyError({ toString: null }, 1);
+
+        if (result !== expectedErrorMessage) {
+            throw new Error(`should throw the error message "${ expectedErrorMessage }", but got: ${ result }`);
+        }
+    });
+
+    it('stringifyError should handle error when something when wrong', () => {
+        const expectedErrorMessage = 'Error while stringifying error';
+        const result = stringifyError({ toString: () => {
+            throw new Error('unexpected error');
+        } }, 2);
+
+        if (!result.startsWith(expectedErrorMessage)) {
+            throw new Error(`should throw the error message starting wit "${ expectedErrorMessage }", but got: ${ result }`);
+        }
+    });
+});
diff --git a/test/tests/util/values.js b/test/tests/util/values.js
new file mode 100644
index 00000000..238676a0
--- /dev/null
+++ b/test/tests/util/values.js
@@ -0,0 +1,25 @@
+/* @flow */
+
+import { values } from '../../../src';
+
+describe('values cases', () => {
+
+    it('should return object values when Object.values is available', () => {
+        const result = values({ a: true });
+
+        if (!result[0]) {
+            throw new Error(`should return the value from the original object, but got: ${ String(result) }`);
+        }
+    });
+
+    it('should return object values when Object.values is unavailable', () => {
+        const originalFunc = Object.values;
+        Reflect.deleteProperty(Object, 'values');
+        const result = values({ a: true });
+
+        if (!result[0]) {
+            throw new Error(`should return the value from the original object, but got: ${ String(result) }`);
+        }
+        Reflect.defineProperty(Object, 'values', originalFunc);
+    });
+});