Fix handling of NaN/Infinity in mock timer delay, #5960

CHANGELOG.md

@@ -87,6 +87,8 @@
   ([#5914](https://github.com/facebook/jest/pull/5914))
 * `[jest-regex-util]` Fix handling regex symbols in tests path on Windows
   ([#5941](https://github.com/facebook/jest/pull/5941))
+* `[jest-util]` Fix handling of NaN/Infinity in mock timer delay
+  ([#5966](https://github.com/facebook/jest/pull/5966))
 
 ### Chore & Maintenance
 

packages/jest-util/src/__tests__/fake_timers.test.js

@@ -315,17 +315,28 @@ describe('FakeTimers', () => {
       const mock2 = jest.fn(() => runOrder.push('mock2'));
       const mock3 = jest.fn(() => runOrder.push('mock3'));
       const mock4 = jest.fn(() => runOrder.push('mock4'));
+      const mock5 = jest.fn(() => runOrder.push('mock5'));
+      const mock6 = jest.fn(() => runOrder.push('mock6'));
 
       global.setTimeout(mock1, 100);
-      global.setTimeout(mock2, 0);
+      global.setTimeout(mock2, NaN);
       global.setTimeout(mock3, 0);
       const intervalHandler = global.setInterval(() => {
         mock4();
         global.clearInterval(intervalHandler);
       }, 200);
+      global.setTimeout(mock5, Infinity);
+      global.setTimeout(mock6, -Infinity);
 
       timers.runAllTimers();
-      expect(runOrder).toEqual(['mock2', 'mock3', 'mock1', 'mock4']);
+      expect(runOrder).toEqual([
+        'mock2',
+        'mock3',
+        'mock5',
+        'mock6',
+        'mock1',
+        'mock4',
+      ]);
     });
 
     it('warns when trying to advance timers while real timers are used', () => {

packages/jest-util/src/fake_timers.js

@@ -486,9 +486,7 @@ export default class FakeTimers<TimerRef> {
       return null;
     }
 
-    if (delay == null) {
-      delay = 0;
-    }
+    delay = Number(delay) | 0;
 
     const args = [];
     for (let ii = 2, ll = arguments.length; ii < ll; ii++) {