queueMarkAsRead: Adapt to use Lolex in tests.

Simplify tests significantly by using Jest.

In addition to changes in the tests proper, this also sets the
internal variable `lastSentTime` to an initial value of `-Infinity`
rather than `0`: Lolex's fake clock is initially set to a time of `0`,
which badly confuses the original code.

(An alternative solution would be to bump Lolex's initial time to some
value greater than 0, but this seems more clearly a hack.)

src/api/__tests__/queueMarkAsRead-test.js

@@ -2,17 +2,26 @@
 import queueMarkAsRead, { resetAll } from '../queueMarkAsRead';
 import * as messagesFlags from '../messages/messagesFlags';
 import * as eg from '../../__tests__/exampleData';
+import { Lolex } from '../../__tests__/aux/lolex';
 
 // $FlowFixMe Make flow understand about mocking
 messagesFlags.default = jest.fn(() => {});
 
-jest.useFakeTimers();
-
 describe('queueMarkAsRead', () => {
-  beforeEach(() => {
-    resetAll();
+  let lolex: Lolex;
+
+  beforeAll(() => {
+    lolex = new Lolex();
+  });
+
+  afterAll(() => {
+    lolex.dispose();
+  });
+
+  afterEach(() => {
     jest.clearAllMocks();
-    jest.clearAllTimers();
+    lolex.clearAllTimers();
+    resetAll();
   });
 
   test('should not call messagesFlags on consecutive calls of queueMarkAsRead,  setTimout on further calls', () => {
@@ -21,36 +30,25 @@ describe('queueMarkAsRead', () => {
     queueMarkAsRead(eg.selfAuth, [7, 8, 9]);
     queueMarkAsRead(eg.selfAuth, [10, 11, 12]);
 
-    expect(setTimeout).toHaveBeenCalledTimes(1);
+    expect(lolex.getTimerCount()).toBe(1);
     expect(messagesFlags.default).toHaveBeenCalledTimes(1);
   });
 
   test('should call messagesFlags, if calls to queueMarkAsRead are 2s apart', () => {
-    const start = Date.now();
-    // $FlowFixMe Make flow understand about mocking
-    Date.now = jest.fn().mockReturnValue(start);
     queueMarkAsRead(eg.selfAuth, [13, 14, 15]);
-
-    // $FlowFixMe Make flow understand about mocking
-    Date.now = jest.fn().mockReturnValue(start + 2100);
+    lolex.advanceTimersByTime(2100);
     queueMarkAsRead(eg.selfAuth, [16, 17, 18]);
 
     expect(messagesFlags.default).toHaveBeenCalledTimes(2);
   });
 
   test('should set timeout for time remaining for next API call to clear queue', () => {
-    const start = Date.now();
-    // $FlowFixMe Make flow understand about mocking
-    Date.now = jest.fn().mockReturnValue(start);
     queueMarkAsRead(eg.selfAuth, [1, 2, 3]);
 
-    // $FlowFixMe Make flow understand about mocking
-    Date.now = jest.fn().mockReturnValue(start + 1900);
+    lolex.advanceTimersByTime(1900);
     queueMarkAsRead(eg.selfAuth, [4, 5, 6]);
 
-    // $FlowFixMe Make flow understand about mocking
-    Date.now = jest.fn().mockReturnValue(start + 2001);
-    jest.runOnlyPendingTimers();
+    lolex.runOnlyPendingTimers();
     expect(messagesFlags.default).toHaveBeenCalledTimes(2);
   });
 });

src/api/queueMarkAsRead.js

@@ -6,13 +6,13 @@ import messagesFlags from './messages/messagesFlags';
 const debouncePeriodMs = 2000;
 
 let unsentMessageIds = [];
-let lastSentTime = 0;
+let lastSentTime = -Infinity;
 let timeout = null;
 
 /** Private; exported only for tests. */
 export const resetAll = () => {
   unsentMessageIds = [];
-  lastSentTime = 0;
+  lastSentTime = -Infinity;
   timeout = null;
 };