fix(expect): accept class instances in toMatchObject and objectContaining (#16196)

.github/copilot-instructions.md

@@ -33,6 +33,7 @@ yarn test-ci-partial:parallel --max-workers <N> --shard=<M>/<N>   # CI-mode shar
 - New test files are `.ts` (some legacy `.js` remain).
 - Each `__tests__/` directory under packages covered by `yarn typecheck:tests` has its own `tsconfig.json` extending `tsconfig.test.json`. Add `"node"` to its `types` array when using Node globals like `Console`/`Stats`/`__dirname`.
 - **`yarn typecheck:tests` is gated in CI** — must exit 0. Adding a new package's tests means appending it to the glob in `package.json`.
+- **Type tests for `expect` matchers belong in `packages/jest-types/__typetests__/expect/`**, not in `packages/expect/__typetests__/`. The `jest-types` suite tests the public `@jest/globals` surface (what users import); `packages/expect/__typetests__/` covers internal `expect`-package concerns only (e.g. `MatcherFunction`, `JestExpect` shape). When adding type tests for matcher signatures, add them to `jest-types`.
 - **E2E tests (`e2e/__tests__/`) can't use `jest.mock`/`jest.fn`** — ESLint enforces this. Use fixture files instead.
 - Some e2e tests need Mercurial: `brew install hg`.
 - **Docblock pragmas** in test files: `@jest-environment <name>` overrides the test environment; `@jest-environment-options {"key": value}` merges into `testEnvironmentOptions`. Both are extracted by `jest-runner` and apply only to that file.

CHANGELOG.md

@@ -9,6 +9,7 @@
 ### Fixes
 
 - `[expect, jest-message-util, jest-pattern, jest-regex-util, jest-util]` Revert `node:` protocol imports to restore webpack/browser-bundle compatibility ([#16167](https://github.com/jestjs/jest/pull/16167))
+- `[expect]` Widen `toMatchObject` and `objectContaining` parameter type from `Record<string, unknown>` to `object` so class instances are accepted ([#16196](https://github.com/jestjs/jest/pull/16196))
 - `[@jest-environment/jsdom-abstract]` Make `@types/jsdom` a peer dependency ([#16166](https://github.com/jestjs/jest/pull/16166))
 - `[jest-runtime]` Fall back to native ESM when a `.js` file contains ESM syntax but has no `"type":"module"` marker ([#16152](https://github.com/jestjs/jest/pull/16152))
 - `[jest-runtime]` Support older test environments whose `moduleMocker` does not implement `clearMocksOnScope` ([#16169](https://github.com/jestjs/jest/pull/16169))

packages/expect/src/types.ts

@@ -119,7 +119,7 @@ export interface AsymmetricMatchers {
   arrayContaining(sample: Array<unknown>): AsymmetricMatcher;
   arrayOf(sample: unknown): AsymmetricMatcher;
   closeTo(sample: number, precision?: number): AsymmetricMatcher;
-  objectContaining(sample: Record<string, unknown>): AsymmetricMatcher;
+  objectContaining(sample: object): AsymmetricMatcher;
   stringContaining(sample: string): AsymmetricMatcher;
   stringMatching(sample: string | RegExp): AsymmetricMatcher;
 }
@@ -298,9 +298,7 @@ export interface Matchers<R extends void | Promise<void>, T = unknown> {
   /**
    * Used to check that a JavaScript object matches a subset of the properties of an object
    */
-  toMatchObject(
-    expected: Record<string, unknown> | Array<Record<string, unknown>>,
-  ): R;
+  toMatchObject(expected: object | Array<object>): R;
   /**
    * Use to test that objects have the same types as well as structure.
    */

packages/jest-types/__typetests__/expect/base.test.ts

@@ -69,6 +69,16 @@ expect(
 expect(
   jestExpect({a: 1}).toEqual(jestExpect.objectContaining({a: 1})),
 ).type.toBe<void>();
+
+class SessionForContaining {
+  id = '';
+}
+expect(
+  jestExpect({id: ''}).toEqual(
+    jestExpect.objectContaining(new SessionForContaining()),
+  ),
+).type.toBe<void>();
+
 expect(
   jestExpect({a: 1}).toEqual(jestExpect.objectContaining(1)),
 ).type.toRaiseError();
@@ -266,6 +276,16 @@ expect(jestExpect({a: 1, b: 2}).toMatchObject({b: 2})).type.toBe<void>();
 expect(
   jestExpect([{a: 1}, {b: 2, c: true}]).toMatchObject([{a: 1}, {b: 2}]),
 ).type.toBe<void>();
+
+class Session {
+  id = '';
+  username = '';
+  userId = 0;
+}
+const session = new Session();
+expect(jestExpect({}).toMatchObject(session)).type.toBe<void>();
+expect(jestExpect({}).toMatchObject([session, session])).type.toBe<void>();
+
 expect(jestExpect({c: true}).toMatchObject(true)).type.toRaiseError();
 expect(jestExpect({c: true}).toMatchObject()).type.toRaiseError();