Add tests for Redux sample code

.eslintrc

@@ -1,8 +1,12 @@
 {
   "extends": "airbnb",
+  "env": {
+    "jest": true
+  },
   "rules": {
     // Apprently react-native doesn't like .jsx files
     "react/jsx-filename-extension": ["error", { "extensions": [".js"] }],
-    "import/prefer-default-export": "off"
+    "import/prefer-default-export": "off",
+    "import/no-extraneous-dependencies": ["error", { devDependencies: true }]
   }
 }

package.json

@@ -23,6 +23,7 @@
 		"rxjs": "^5.5.6"
 	},
 	"devDependencies": {
+		"axios-mock-adapter": "^1.10.0",
 		"babel-jest": "21.2.0",
 		"babel-preset-react-native": "4.0.0",
 		"eslint": "^4.9.0",
@@ -36,7 +37,10 @@
 		"react-test-renderer": "16.0.0-beta.5"
 	},
 	"jest": {
-		"preset": "react-native"
+		"preset": "react-native",
+		"transformIgnorePatterns": [
+			"node_modules/(?!(jest-)?react-native|react-navigation)"
+		]
 	},
 	"comment": "flow is disabled in pre-commit because react-navigation breaks it",
 	"pre-commit": [

src/state/ducks/auth/selectors.js

@@ -0,0 +1,3 @@
+export function isAuthenticated(state) {
+  return state.auth.authenticated;
+}

src/state/ducks/auth/test.js

@@ -0,0 +1,26 @@
+import configureStore from '../../store';
+import * as actions from './actions';
+import * as selectors from './selectors';
+
+let store;
+
+beforeEach(() => {
+  store = configureStore({ noEpic: true });
+});
+
+test('user is initially not logged in', () => {
+  expect(selectors.isAuthenticated(store.getState())).toBe(false);
+});
+
+test('login() logs the user in', () => {
+  store.dispatch(actions.login());
+  expect(selectors.isAuthenticated(store.getState())).toBe(true);
+});
+
+test('logout() logs the user out', () => {
+  store.dispatch(actions.login());
+  expect(selectors.isAuthenticated(store.getState())).toBe(true);
+
+  store.dispatch(actions.logout());
+  expect(selectors.isAuthenticated(store.getState())).toBe(false);
+});

src/state/ducks/patreon/test.js

@@ -0,0 +1,112 @@
+import { ActionsObservable } from 'redux-observable';
+import axios from 'axios';
+import MockAdapter from 'axios-mock-adapter';
+
+import configureStore from '../../store';
+import * as types from './types';
+import * as actions from './actions';
+import * as selectors from './selectors';
+import epic from './epic';
+
+/*
+ * Reducers are tested by stubbing out the epic with one that does nothing,
+ * and then asserting things about the synchronous actions only. Later,
+ * we test that the epics emit those synchronous actions in response
+ * to the async stuff they do, which closes the loop and effectively
+ * tests that dispatching the async action that the epic handled
+ * eventually caused the expected state change.
+ *
+ * This is a lot simpler than trying to test the entire store
+ * with the redux-observable middleware installed, and it gives us
+ * the same coverage.
+ */
+
+describe('patreon reducer', () => {
+  let store;
+
+  beforeEach(() => {
+    store = configureStore({ noEpic: true });
+  });
+
+  test('patreon is initially not enabled', () => {
+    expect(selectors.isPatron(store.getState())).toBe(false);
+  });
+
+  test('patreonEnabled() enables patreon', () => {
+    store.dispatch(actions.patreonEnabled());
+    expect(selectors.isPatron(store.getState())).toBe(true);
+  });
+
+  test('patreonDisabled() disables patreon', () => {
+    store.dispatch(actions.patreonEnabled());
+    expect(selectors.isPatron(store.getState())).toBe(true);
+
+    store.dispatch(actions.patreonDisabled());
+    expect(selectors.isPatron(store.getState())).toBe(false);
+  });
+});
+
+
+/*
+ * Direct epic tests are very simple. An epic is just a function
+ * that accepts an ActionsObservable and returns an Observable.
+ * A test for an epic therefore just has to:
+ * 1) Create an ActionObservable that emits the action(s) you want to test
+ * 2) Assert that the Observable the epic returns emits the expected action(s)
+ */
+
+describe('patreon epic', () => {
+  const baseUrl = 'https://httpbin.org';
+  let mock;
+
+  beforeEach(() => {
+    mock = new MockAdapter(axios);
+  });
+
+  // These tests are very simple; one action leads to a single other.
+  // Other tests that result in multiple actions from the epic
+  // will have to be a little more complicated.
+
+  describe('when Patreon API call succeeds', () => {
+    beforeEach(() => {
+      mock.onPost(new RegExp(`${baseUrl}/.*`)).reply(200, {});
+    });
+
+    test('enable() leads to patreonEnabled()', () => {
+      const action$ = ActionsObservable.of(actions.enable());
+      return expect(epic(action$).toPromise()).resolves.toEqual(actions.patreonEnabled());
+    });
+
+    test('disable() leads to patreonDisabled()', () => {
+      const action$ = ActionsObservable.of(actions.disable());
+      return expect(epic(action$).toPromise()).resolves.toEqual(actions.patreonDisabled());
+    });
+  });
+
+  describe('when Patreon API call fails', () => {
+    const status = 429;
+
+    beforeEach(() => {
+      mock.onPost(new RegExp(`${baseUrl}/.*`)).reply(status, {});
+    });
+
+    function expectErrorActionWithStatus(action, statusCode) {
+      expect(action.type).toEqual(types.PATREON_ERROR);
+      expect(action.error).toBe(true);
+      expect(action.payload).toBeInstanceOf(Error);
+      expect(action.payload.response.status).toEqual(statusCode);
+    }
+
+    test('enable() leads to patreonError()', async () => {
+      const action$ = ActionsObservable.of(actions.enable());
+      const errorAction = await epic(action$).toPromise();
+      expectErrorActionWithStatus(errorAction, status);
+    });
+
+    test('disable() leads to patreonError()', async () => {
+      const action$ = ActionsObservable.of(actions.disable());
+      const errorAction = await epic(action$).toPromise();
+      expectErrorActionWithStatus(errorAction, status);
+    });
+  });
+});

src/state/store.js

@@ -1,13 +1,27 @@
 import { combineReducers, createStore, applyMiddleware } from 'redux';
 import { composeWithDevTools } from 'redux-devtools-extension';
 import { combineEpics, createEpicMiddleware } from 'redux-observable';
+import { Observable } from 'rxjs';
+import 'rxjs/add/observable/never';
 
 import * as reducers from './ducks';
 import epics from './epics';
 
-export default function configureStore() {
+/**
+ * A fake epic that just swallows actions. Useful for synchronous unit tests.
+ */
+const emptyEpic = () => Observable.never();
+
+/**
+ * Return a redux store configured with all the reducers and middleware.
+ *
+ * If noEpic is passed, use emptyEpic to swallow all async actions.
+ * This allows testing the store with just synchronous actions,
+ * not worrying about side effects.
+ */
+export default function configureStore({ noEpic = false }) {
   const reducer = combineReducers(reducers);
-  const epic = combineEpics(...epics);
+  const epic = noEpic ? combineEpics(...epics) : emptyEpic;
   const epicMiddleware = createEpicMiddleware(epic);
   const enhancer = composeWithDevTools(applyMiddleware(epicMiddleware));
   return createStore(reducer, enhancer);

yarn.lock

@@ -259,6 +259,12 @@ aws4@^1.2.1, aws4@^1.6.0:
   version "1.6.0"
   resolved "https://registry.yarnpkg.com/aws4/-/aws4-1.6.0.tgz#83ef5ca860b2b32e4a0deedee8c771b9db57471e"
 
+axios-mock-adapter@^1.10.0:
+  version "1.10.0"
+  resolved "https://registry.yarnpkg.com/axios-mock-adapter/-/axios-mock-adapter-1.10.0.tgz#3ccee65466439a2c7567e932798fc0377d39209d"
+  dependencies:
+    deep-equal "^1.0.1"
+
 axios@^0.17.1:
   version "0.17.1"
   resolved "https://registry.yarnpkg.com/axios/-/axios-0.17.1.tgz#2d8e3e5d0bdbd7327f91bc814f5c57660f81824d"
@@ -1369,6 +1375,10 @@ decamelize@^1.0.0, decamelize@^1.1.1:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/decamelize/-/decamelize-1.2.0.tgz#f6534d15148269b20352e7bee26f501f9a191290"
 
+deep-equal@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/deep-equal/-/deep-equal-1.0.1.tgz#f5d260292b660e084eff4cdbc9f08ad3247448b5"
+
 deep-extend@~0.4.0:
   version "0.4.2"
   resolved "https://registry.yarnpkg.com/deep-extend/-/deep-extend-0.4.2.tgz#48b699c27e334bf89f10892be432f6e4c7d34a7f"