Get setTimeout lazily (#20)

* Get setTimeout and Date.now lazily

This prevents from using old versions of setTimeout/Date.now

* Modify withFakeTimers unit test to cover the correct scenario

BREAKING CHANGE: If you combined fake timers with wait-for-expect that will most probably not work anymore. Please make an issue with your failing usecase, as we couldn't think of a situation where using wait-for-expect and fake timers in the same test would be necessary.

Author: brapifra

src/index.ts

@@ -1,8 +1,3 @@
-// Used to avoid using Jest's fake timers and Date.now mocks
-// See https://github.com/TheBrainFamily/wait-for-expect/issues/4 and
-// https://github.com/TheBrainFamily/wait-for-expect/issues/12 for more info
-const { setTimeout } = typeof window !== "undefined" ? window : global;
-
 const defaults = {
   timeout: 4500,
   interval: 50
@@ -21,6 +16,11 @@ const waitForExpect = function waitForExpect(
   timeout = defaults.timeout,
   interval = defaults.interval
 ) {
+  // Used to avoid using Jest's fake timers and Date.now mocks
+  // See https://github.com/TheBrainFamily/wait-for-expect/issues/4 and
+  // https://github.com/TheBrainFamily/wait-for-expect/issues/12 for more info
+  const { setTimeout } = typeof window !== "undefined" ? window : global;
+
   // eslint-disable-next-line no-param-reassign
   if (interval < 1) interval = 1;
   const maxTries = Math.ceil(timeout / interval);

src/withFakeTimers.spec.ts

@@ -7,12 +7,17 @@ import waitForExpect from "./index";
 // line from the index.ts
 
 beforeEach(() => {
+  jest.resetModules();
   jest.restoreAllMocks();
   jest.useRealTimers();
 });
 
-test("it works even if the timers are overwritten by jest", async () => {
+test("it works with real timers even if they were set to fake before importing the module", async () => {
   jest.useFakeTimers();
+  /* eslint-disable global-require */
+  const importedWaitForExpect = require("./index");
+  jest.useRealTimers();
+
   let numberToChange = 10;
   // we are using random timeout here to simulate a real-time example
   // of an async operation calling a callback at a non-deterministic time
@@ -22,8 +27,7 @@ test("it works even if the timers are overwritten by jest", async () => {
     numberToChange = 100;
   }, randomTimeout);
 
-  jest.runAllTimers();
-  await waitForExpect(() => {
+  await importedWaitForExpect(() => {
     expect(numberToChange).toEqual(100);
   });
 });