Benoit/mock

[BenoitZugmeyer]

Motivation

This is a proposal to allow mocking values (mostly functions) within tests.

The current way to mock values used within a function is to pass them as argument of that function. For example:

// foo.ts
import { startBar } from 'bar'

function createFoo(startBarImpl = startBar) {
  const bar = startBarImpl()
}


// foo.spec.ts
it('create foo', () => {
  createFoo(mockStartBar)
})

However, forces to have unecessary extra arguments in functions. Impls also need to be propagated within subfunctions:

// foo.ts
function createFoo(startBarImpl = startBar) {
  const baz = trackBaz(startBarImpl)
}

// baz.ts
function trackBaz(startBarImpl = startBar) {
}

This PR introduce a new way to mock values that is similar to a lightweight dependency injection system. Values that can be mocked should be wrapped in a mocked() call when used, and tests can use mockValue() to replace the value or mockWithSpy() to replace it with a jasmine spy. The example above would be implemented as:

// foo.ts
import { startBar } from 'bar'

function createFoo() {
  const bar = mockable(startBar)()
}

// foo.spec.ts
it('create foo', () => {
  replaceMockable(startBar, mockStartBar)
  // or
  replaceMockableWithSpy(startBar).and.callFake(mockStartBar)
  createFoo()
})

Changes

Test instructions

Checklist

• Tested locally
• Tested on staging
• Added unit tests for this change.
• Added e2e/integration tests for this change.
• Updated documentation and/or relevant AGENTS.md file

[datadog-datadog-prod-us1]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage
• Patch Coverage: 91.30%
• Overall Coverage: 77.27% (+0.00%)

View detailed report

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[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	167.98 KiB	168.07 KiB	+98 B	+0.06%	✅
Rum Profiler	4.32 KiB	4.32 KiB	0 B	0.00%	✅
Rum Recorder	24.54 KiB	24.54 KiB	0 B	0.00%	✅
Logs	56.25 KiB	56.16 KiB	-86 B	-0.15%	✅
Flagging	944 B	944 B	0 B	0.00%	✅
Rum Slim	124.88 KiB	124.82 KiB	-61 B	-0.05%	✅
Worker	23.63 KiB	23.63 KiB	0 B	0.00%	✅

🚀 CPU Performance

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🧠 Memory Performance

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🔗 RealWorld