fix: delegate prototype mock call

packages/vitest/src/runtime/mocker.ts

@@ -328,16 +328,20 @@ export class VitestMocker {
           const spyModule = this.spyModule
           if (!spyModule)
             throw this.createError('[vitest] `spyModule` is not defined. This is Vitest error. Please open a new issue with reproduction.')
-          const mock = spyModule.spyOn(newContainer, property).mockImplementation(function (this: any) {
-            // do similar to ject? https://github.com/jestjs/jest/blob/2c3d2409879952157433de215ae0eee5188a4384/packages/jest-mock/src/index.ts#L678-L691
+          const mock = spyModule.spyOn(newContainer, property).mockImplementation(function (this: any, ...args: any[]) {
+            // jest reference
+            // https://github.com/jestjs/jest/blob/2c3d2409879952157433de215ae0eee5188a4384/packages/jest-mock/src/index.ts#L678-L691
+
             // check constructor call
             if (this instanceof newContainer[property]) {
               // mock each class instance's method
               // TODO: more sound way to loop prorotype methods?
               for (const key in this) {
                 if (typeof this[key] === 'function') {
                   // TODO: ability to restore?
-                  spyModule.spyOn(this, key).mockImplementation(() => undefined)
+                  // mock but delegate to original prototype method, which should be also mocked already
+                  const original = this[key]
+                  spyModule.spyOn(this, key).mockImplementation(() => original.apply(this, args))
                 }
               }
             }

test/core/src/mockedE.ts

@@ -1,5 +1,5 @@
 export class MockedE {
-  public doSomething() {
-    return 'hello'
+  public doSomething(arg: string) {
+    return arg.repeat(2)
   }
 }

test/core/test/mocked-wip.test.ts

@@ -4,7 +4,7 @@ import { MockedE } from '../src/mockedE'
 
 vi.mock('../src/mockedE')
 
-// TODO: move to mocked.test.ts
+// TODO: move to mocked.test.ts?
 
 test('mock each instance method separately', () => {
   expect(MockedE).toBeTypeOf('function')
@@ -16,8 +16,19 @@ test('mock each instance method separately', () => {
   expect(instance1.doSomething).not.toBe(MockedE.prototype.doSomething)
   expect(vi.mocked(instance1.doSomething).mock).not.toBe(vi.mocked(instance2.doSomething).mock)
 
-  instance1.doSomething()
+  // TODO: check input/output
+  instance1.doSomething('a')
   expect(instance1.doSomething).toBeCalledTimes(1)
   expect(instance2.doSomething).toBeCalledTimes(0)
-  expect(MockedE.prototype.doSomething).toBeCalledTimes(0)
+  expect(MockedE.prototype.doSomething).toBeCalledTimes(1)
+
+  instance2.doSomething('b')
+  expect(instance1.doSomething).toBeCalledTimes(1)
+  expect(instance2.doSomething).toBeCalledTimes(1)
+  expect(MockedE.prototype.doSomething).toBeCalledTimes(2)
+
+  instance1.doSomething('c')
+  expect(instance1.doSomething).toBeCalledTimes(2)
+  expect(instance2.doSomething).toBeCalledTimes(1)
+  expect(MockedE.prototype.doSomething).toBeCalledTimes(3)
 })

test/core/test/mocked.test.ts

@@ -76,8 +76,7 @@ describe('mocked classes', () => {
     expect(instance.doSomething).toBeTypeOf('function')
     expect(instance.doSomething()).not.toBe('A')
 
-    // TODO: check what jest does
-    expect(MockedC.prototype.doSomething).not.toHaveBeenCalledOnce()
+    expect(MockedC.prototype.doSomething).toHaveBeenCalledOnce()
     expect(MockedC.prototype.doSomething).not.toHaveReturnedWith('A')
   })