Jest spy doesn't work on Microservices Controller (EventPattern) E2E Tests

Is there an existing issue for this?

[X] I have searched the existing issues

Current behavior

Spying on Controller instance - handler is called but spy does not track it
Spying on Controller prototype before app is initialized - handler is not called
Spying on Controller prototype after app is initialized - handler is called but spy does not track it

Minimum reproduction code

https://github.com/elton-okawa/nestjs-spy-controller-issue

Steps to reproduce

npm install

// run all tests
npm run test:e2e

// run individual tests (better to see logs)
npm run test:e2e -- -t 'should spy controller instance'
npm run test:e2e -- -t 'should spy controller prototype before init'
npm run test:e2e -- -t 'should spy controller prototype after init'

Expected behavior

From a similar issue comment: https://github.com/nestjs/nest/issues/8790#issuecomment-994480901 (As the comment suggests, I couldn't find any related issue besides this one)

Long story short: you can spy on/mock service methods. You can't spy on/mock controller methods (annotated methods) after your app is initialized (execution context is created).

I understood that it's possible to spy/mock annotated methods as long as you do it before the app is initialized, so behavior (1) and (3) is expected to fail, but not (2)

Package

[ ] I don't know. Or some 3rd-party package
[ ] code>@nestjs/common</code
[X] code>@nestjs/core</code
[X] code>@nestjs/microservices</code
[ ] code>@nestjs/platform-express</code
[ ] code>@nestjs/platform-fastify</code
[ ] code>@nestjs/platform-socket.io</code
[ ] code>@nestjs/platform-ws</code
[X] code>@nestjs/testing</code
[ ] code>@nestjs/websockets</code
[ ] Other (see below)

Other package

No response

NestJS version

10.3.8

Packages versions

[System Information]
OS Version     : Linux 5.15.146.1-microsoft-standard-WSL2
NodeJS Version : v20.11.1
NPM Version    : 10.2.4

[Nest CLI]
Nest CLI Version : 10.3.2

[Nest Platform Information]
platform-express version : 10.3.8
microservices version    : 10.3.8
schematics version       : 10.1.1
testing version          : 10.3.8
common version           : 10.3.8
core version             : 10.3.8
cli version              : 10.3.2

Node.js version

20.11.1

In which operating systems have you tested?

[ ] macOS
[ ] Windows
[X] Linux

Other

Spying on Controller instance - handler is called but spy does not track it


[Nest] 47442  - 04/21/2024, 7:28:41 AM   DEBUG [E2E Test] Producing message...
[Nest] 47442  - 04/21/2024, 7:28:41 AM   DEBUG [E2E Test] Message produced successfully!
[Nest] 47442  - 04/21/2024, 7:28:41 AM   DEBUG [E2E Test] Waiting "message to be consumed" for 10000ms...
[Nest] 47442  - 04/21/2024, 7:28:41 AM     LOG [AppService] Message received: "spy controller instance"
[Nest] 47442  - 04/21/2024, 7:28:51 AM   DEBUG [E2E Test] Finished waiting for "message to be consumed"
[Nest] 47442  - 04/21/2024, 7:28:51 AM   DEBUG [E2E Test] Message should be consumed at this point
...

● AppController (e2e) › controller › should spy controller instance

expect(jest.fn()).toHaveBeenCalledTimes(expected)

Expected number of calls: 1
Received number of calls: 0

  60 |       await produceEventAndWait(producer, 'spy controller instance');
  61 |
> 62 |       expect(handlerSpy).toHaveBeenCalledTimes(1);
     |                          ^
  63 |     });
  64 |
  65 |     it('should spy controller prototype before init', async () => {

  at Object.<anonymous> (test/app.e2e-spec.ts:62:26)

Test Suites: 1 failed, 1 total Tests: 1 failed, 5 skipped, 6 total Snapshots: 0 total Time: 44.32 s, estimated 249 s Ran all test suites with tests matching "should spy controller instance".


2. Spying on `Controller` **prototype before** app is initialized - handler is not called

[Nest] 48666 - 04/21/2024, 7:31:55 AM DEBUG [E2E Test] Producing message... [Nest] 48666 - 04/21/2024, 7:31:55 AM DEBUG [E2E Test] Message produced successfully! [Nest] 48666 - 04/21/2024, 7:31:55 AM DEBUG [E2E Test] Waiting "message to be consumed" for 10000ms... [Nest] 48666 - 04/21/2024, 7:32:05 AM DEBUG [E2E Test] Finished waiting for "message to be consumed" [Nest] 48666 - 04/21/2024, 7:32:05 AM DEBUG [E2E Test] Message should be consumed at this point ...

● AppController (e2e) › controller › should spy controller prototype before init

expect(jest.fn()).toHaveBeenCalledTimes(expected)

Expected number of calls: 1
Received number of calls: 0

  72 |       );
  73 |
> 74 |       expect(handlerSpy).toHaveBeenCalledTimes(1);
     |                          ^
  75 |     });
  76 |
  77 |     it('should spy controller prototype after init', async () => {

  at Object.<anonymous> (test/app.e2e-spec.ts:74:26)

Test Suites: 1 failed, 1 total Tests: 1 failed, 5 skipped, 6 total Snapshots: 0 total Time: 51.975 s Ran all test suites with tests matching "spy controller prototype before init".


3. Spying on `Controller` **prototype after** app is initialized - handler is called but spy does not track it

[Nest] 49480 - 04/21/2024, 7:33:57 AM DEBUG [E2E Test] Producing message... [Nest] 49480 - 04/21/2024, 7:33:57 AM DEBUG [E2E Test] Message produced successfully! [Nest] 49480 - 04/21/2024, 7:33:57 AM DEBUG [E2E Test] Waiting "message to be consumed" for 10000ms... [Nest] 49480 - 04/21/2024, 7:33:57 AM LOG [AppService] Message received: "spy controller prototype after init" [Nest] 49480 - 04/21/2024, 7:34:07 AM DEBUG [E2E Test] Finished waiting for "message to be consumed" [Nest] 49480 - 04/21/2024, 7:34:07 AM DEBUG [E2E Test] Message should be consumed at this point ...

● AppController (e2e) › controller › should spy controller prototype after init

expect(jest.fn()).toHaveBeenCalledTimes(expected)

Expected number of calls: 1
Received number of calls: 0

  84 |       );
  85 |
> 86 |       expect(handlerSpy).toHaveBeenCalledTimes(1);
     |                          ^
  87 |     });
  88 |   });
  89 | });

  at Object.<anonymous> (test/app.e2e-spec.ts:86:26)

Test Suites: 1 failed, 1 total Tests: 1 failed, 5 skipped, 6 total Snapshots: 0 total Time: 44.39 s, estimated 52 s Ran all test suites with tests matching "spy controller prototype after init".

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