refactor(timetravel): move animation timetravel helper into a seperate file

Author: thecodecafe

setupJest.js

@@ -1,6 +1,5 @@
 import 'abortcontroller-polyfill/dist/abortcontroller-polyfill-only';
 require('jest-fetch-mock').enableMocks();
-const MockDate = require('mockdate');
 const frameTime = 1;
 
 jest.mock('react-native/Libraries/Alert/Alert', () => {
@@ -18,19 +17,6 @@ jest.mock('react-native/Libraries/Utilities/Dimensions', () => {
   };
 });
 
-// global time travel mock for mocking "RN Animated" fram steps;
-global.timeTravel = (time = frameTime) => {
-  // tick travel handler
-  const tickTravel = () => {
-    // move time forward by number of fram time ms
-    const now = Date.now();
-    MockDate.set(new Date(now + frameTime));
-    // run the timers forward
-    jest.advanceTimersByTime(frameTime);
-  }
-  // step through each of the frames
-  const frames = time / frameTime;
-  for (let i = 0; i < frames; i++) {
-      tickTravel();
-  }
-};
+global.requestAnimationFrame = cb => {
+  setTimeout(cb, frameTime)
+}

timeTravel.js

@@ -0,0 +1,26 @@
+const MockDate = require('mockdate');
+export const FRAME_TIME = 1;
+
+const advanceOneFrame = () => {
+  MockDate.set(new Date(Date.now() + FRAME_TIME))
+  jest.advanceTimersByTime(FRAME_TIME)
+}
+
+// global time travel mock for mocking "RN Animated" fram steps;
+const timeTravel = (msToAdvance = FRAME_TIME) => {
+  const numberOfFramesToRun = msToAdvance / FRAME_TIME
+  let framesElapsed = 0
+
+  // Step through each of the frames until we've ran them all
+  while (framesElapsed < numberOfFramesToRun) {
+    advanceOneFrame()
+    framesElapsed++
+  }
+}
+
+export const setupTimeTravel = () => {
+  MockDate.set(0)
+  jest.useFakeTimers()
+}
+
+export default timeTravel