fix(leak-detector): wait more ticks for GC to run (#10366)

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 ### Fixes
 
+- `[jest-leak-detector]` Wait properly for GC runs due to changes in Node 14.7 ([#10366](https://github.com/facebook/jest/pull/10366))
 - `[jest-worker]` Downgrade minimum node version to 10.13 ([#10352](https://github.com/facebook/jest/pull/10352))
 
 ### Chore & Maintenance

packages/jest-leak-detector/src/index.ts

@@ -7,9 +7,12 @@
 
 import {setFlagsFromString} from 'v8';
 import {runInNewContext} from 'vm';
+import {promisify} from 'util';
 import prettyFormat = require('pretty-format');
 import {isPrimitive} from 'jest-get-type';
 
+const tick = promisify(setImmediate);
+
 export default class {
   private _isReferenceBeingHeld: boolean;
 
@@ -46,12 +49,15 @@ export default class {
     value = null;
   }
 
-  isLeaking(): Promise<boolean> {
+  async isLeaking(): Promise<boolean> {
     this._runGarbageCollector();
 
-    return new Promise(resolve =>
-      setImmediate(() => resolve(this._isReferenceBeingHeld)),
-    );
+    // wait some ticks to allow GC to run properly, see https://github.com/nodejs/node/issues/34636#issuecomment-669366235
+    for (let i = 0; i < 10; i++) {
+      await tick();
+    }
+
+    return this._isReferenceBeingHeld;
   }
 
   private _runGarbageCollector() {