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Test cases should be reviewed as part of the pull request because they encode the change’s intended behavior and shape how much confidence a team can place in it. A reviewer checks whether tests are clear, appropriate, and likely to provide useful evidence; automated checks execute them. Neither replaces the other.
Why tests belong in the pull request review
A pull request changes more than production code. Its tests also become part of the codebase: they describe expected behavior, preserve assumptions, and influence how safely future developers can modify the system.
Google’s code review guidance asks reviewers to assess whether automated tests are correct and well-designed, alongside other dimensions of the change. Microsoft’s engineering playbook describes pull requests as a way to inspect code and qualify it through automation, including unit and integration tests, and recommends including tests related to the production change. Google code review guidance and Microsoft’s pull request guidance both treat testing as part of the review workflow, not an unrelated afterthought.
The analogy is useful because tests are code with a purpose. Reviewing them can expose unclear expectations or assumptions that the production implementation alone does not make obvious. It also gives the team a chance to assess whether the tests will remain understandable and maintainable.
What a reviewer should examine in a test
Reviewing a test is a design and reasoning task, not simply confirming that a test file exists. Consider these questions in the context of the behavior changed:
- Intent: What behavior or risk is the test meant to cover? Is that intent apparent from its name, setup, and expected result?
- Meaningful outcomes: Does it check an observable result that matters, rather than merely exercising code or confirming an implementation detail?
- Regression sensitivity: Would the test fail if the relevant behavior were wrong? Are its assertions specific enough to catch the regression this change could introduce?
- Relevant cases: Are important boundaries or failure paths represented when they matter to the changed behavior?
- Reliability: Does the test depend unnecessarily on timing, execution order, shared state, or external conditions?
- Maintainability: Can another developer understand the setup, inputs, and expected outcome without reconstructing the author’s assumptions?
- Coverage of the change: Does the pull request include the tests related to its production change, and do automated checks run them?
These questions apply the official guidance’s emphasis on correct, well-designed tests; they are practical review prompts, not a checklist published verbatim by Google or Microsoft.
Human review and automated execution do different jobs
Reviewers can reason about intent and design: whether a test represents the behavior the change claims to support, whether its assertions are useful, and whether it is understandable. Automated test execution checks the cases by running them and reports whether they pass in the configured environment. A passing run does not by itself establish that the tests cover the right behavior, while a human review does not execute every case or guarantee correctness.
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Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →That distinction matters. A 2015 Microsoft Research publication argues that code review often does not find functionality issues that should block submission, and discusses the importance of reviewer skills and social context. The paper’s discussion of code-review limits is a reason not to treat review as a substitute for automated testing—or as a reliable bug detector on its own.
Keep the change focused and choose a capable reviewer
Tests are easier to assess when the pull request is compact and focused. Microsoft recommends focused changes and related tests, helping reviewers connect a production-code change to the behavior intended to protect it. If test intent is buried in a broad or unrelated diff, that connection becomes harder to evaluate.
Reviewer capability also matters. Google recommends selecting someone able to provide a thorough and correct review, and Microsoft Research likewise highlights the skills needed for effective review. The useful reviewer is not merely someone available: they should be able to reason about the behavior, risks, and test design involved in the change. Google’s reviewer guidance explains that selection principle.
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How to apply this in a pull request
- Connect each test to a behavior. Identify the intended behavior or risk and make sure the test’s inputs and expected outcome express it clearly.
- Read the assertions, not just the test name. Check that they would distinguish the intended result from a plausible wrong result.
- Look for relevant gaps and fragility. Consider boundaries or failure paths introduced by the change, and watch for unnecessary timing, ordering, shared-state, or external dependencies.
- Check the change as a whole. Confirm that related tests appear with the production change and that the project’s automated checks execute them.
- Ask for the right expertise when needed. If the behavior or test design is outside your ability to assess thoroughly, involve a reviewer who can.
This keeps the review focused on evidence: whether the tests communicate the intended behavior and are designed to help detect relevant regressions, while automation supplies the execution results.
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