test: cover the background/foreground socket resume path

app/lib/store/__tests__/appStateMiddleware.test.ts

@@ -0,0 +1,85 @@
+jest.mock('react-native', () => ({
+	AppState: {
+		currentState: 'unknown',
+		addEventListener: jest.fn()
+	}
+}));
+
+jest.mock('../../notifications', () => ({
+	removeNotificationsAndBadge: jest.fn(() => Promise.resolve())
+}));
+
+import { AppState } from 'react-native';
+
+import applyAppStateMiddleware from '../appStateMiddleware';
+import { APP_STATE } from '../../../actions/actionsTypes';
+
+function setupStore() {
+	const dispatch = jest.fn();
+	const createStore = jest.fn(() => ({ dispatch }));
+	applyAppStateMiddleware()(createStore)();
+	const [, notifyAppState] = (AppState.addEventListener as jest.Mock).mock.calls[0];
+	jest.runOnlyPendingTimers();
+	dispatch.mockClear();
+	return { dispatch, notifyAppState };
+}
+
+function dispatchedTypes(dispatch: jest.Mock) {
+	return dispatch.mock.calls.map(([action]) => action.type);
+}
+
+describe('app state changes', () => {
+	beforeEach(() => {
+		jest.useFakeTimers();
+		jest.clearAllMocks();
+	});
+
+	afterEach(() => {
+		jest.useRealTimers();
+	});
+
+	it('tells the app it came to the foreground', () => {
+		const { dispatch, notifyAppState } = setupStore();
+
+		notifyAppState('active');
+
+		expect(dispatchedTypes(dispatch)).toEqual([APP_STATE.FOREGROUND]);
+	});
+
+	it('tells the app it went to the background', () => {
+		const { dispatch, notifyAppState } = setupStore();
+
+		notifyAppState('background');
+
+		expect(dispatchedTypes(dispatch)).toEqual([APP_STATE.BACKGROUND]);
+	});
+
+	it('stays silent while the app is only temporarily interrupted', () => {
+		const { dispatch, notifyAppState } = setupStore();
+
+		notifyAppState('inactive');
+
+		expect(dispatchedTypes(dispatch)).toEqual([]);
+	});
+
+	it('keeps the foreground state through a temporary interruption', () => {
+		const { dispatch, notifyAppState } = setupStore();
+
+		notifyAppState('active');
+		notifyAppState('inactive');
+		notifyAppState('active');
+
+		expect(dispatchedTypes(dispatch)).toEqual([APP_STATE.FOREGROUND]);
+	});
+
+	it('does not repeat the state already in effect', () => {
+		const { dispatch, notifyAppState } = setupStore();
+
+		notifyAppState('background');
+		notifyAppState('background');
+		notifyAppState('active');
+		notifyAppState('active');
+
+		expect(dispatchedTypes(dispatch)).toEqual([APP_STATE.BACKGROUND, APP_STATE.FOREGROUND]);
+	});
+});