Rule proposal: `jest/prefer-strict-mock-assertions`

[nicolasgillot]

Problem

Developers often use toHaveBeenCalledWith() without verifying the call count, leading to tests that pass when a mock is called multiple times unexpectedly.

Solution

Require toHaveBeenCalledTimes() when using toHaveBeenCalledWith() to ensure complete mock validation.

Examples

// ❌ Potentially flaky - passes if called 1 + times
expect(mockFn).toHaveBeenCalledWith(expectedArg)

// ✅ Explicit and safe - ensures exact call count
expect(mockFn).toHaveBeenCalledTimes(1)
expect(mockFn).toHaveBeenCalledWith(expectedArg)

Benefits

• Prevents false positives in tests
• Makes test intentions explicit
• Improves test reliability and maintainability
• Follows testing best practices

Are you willing to implement this rule? Yes

[G-Rath]

yeah I guess I could see this being useful - not sure about the name though, maybe something like pair-to-have-been-called-assertions?

[nicolasgillot]

Great point about the naming! pair-to-have-been-called-assertions is indeed more specific and descriptive.

It clearly indicates that the rule ensures pairing toHaveBeenCalledWith() with toHaveBeenCalledTimes().

I'll go with that name for the implementation. Should I proceed with creating a PR?

[SimenB]

PR very much welcome, yeah 😀