fix: make leak-detector more aggressive when running GC (#14526)

Author: SimenB

CHANGELOG.md

@@ -4,6 +4,8 @@
 
 ### Fixes
 
+- `[jest-leak-detector]` Make leak-detector more aggressive when running GC ([#14526](https://github.com/jestjs/jest/pull/14526))
+
 ### Performance
 
 ### Chore & Maintenance

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

@@ -7,6 +7,11 @@
 
 import LeakDetector from '../index';
 
+jest.mock('v8', () => ({
+  ...(jest.requireActual('v8') as Record<string, unknown>),
+  getHeapSnapshot: jest.fn(),
+}));
+
 const gc = globalThis.gc;
 
 // Some tests override the "gc" value. Let's make sure we roll it back to its

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

@@ -7,7 +7,7 @@
 /// <reference lib="es2021.WeakRef" />
 
 import {promisify} from 'util';
-import {setFlagsFromString} from 'v8';
+import {getHeapSnapshot, setFlagsFromString} from 'v8';
 import {runInNewContext} from 'vm';
 import {isPrimitive} from 'jest-get-type';
 import {format as prettyFormat} from 'pretty-format';
@@ -48,6 +48,17 @@ export default class LeakDetector {
       await tick();
     }
 
+    if (this._isReferenceBeingHeld) {
+      // triggering a heap snapshot is more aggressive than just `global.gc()`,
+      // but it's also quite slow, so only do it if we still think we're leaking.
+      // https://github.com/nodejs/node/pull/48510#issuecomment-1719289759
+      getHeapSnapshot();
+
+      for (let i = 0; i < 10; i++) {
+        await tick();
+      }
+    }
+
     return this._isReferenceBeingHeld;
   }