Glossary
Diff-aware testing is an approach where E2E tests are automatically generated or selected based on the specific code changes in a pull request. Instead of running a full 500-test suite on every PR, the system analyzes which files changed, maps them to affected user flows, and runs only the tests that are relevant to those changes. The result is faster CI feedback (minutes instead of hours) and higher signal-to-noise ratio (every test that runs is relevant to what changed).
Most CI pipelines run the entire E2E suite on every PR regardless of what changed. A CSS tweak to the settings page triggers 500 tests including checkout, onboarding, and admin flows that are completely unrelated. This wastes CI time (45 min full suite vs 5 min targeted), generates irrelevant flaky failures that erode trust, and makes engineers wait for feedback that doesn’t tell them anything useful about their change. Diff-aware testing eliminates this waste by only running what matters.
Most teams don’t have diff-aware testing at all. They either run the full suite (slow, noisy) or manually tag tests with labels and select subsets via CI config (fragile, gets out of date). Launchable and Buildkite Test Analytics offer predictive test selection based on historical failure data, but they optimize for speed, not coverage — they skip tests that usually pass rather than selecting tests that are relevant to the change. No mainstream tool maps code changes to affected user flows.
Zerocheck reads the PR diff, identifies which components and user flows are affected by the code changes, and generates or selects only the tests that cover those flows. Each PR gets a confidence score — not just pass/fail — that accounts for what changed and how reliable the results are. Tests that are unrelated to the change are skipped entirely, reducing CI time while increasing coverage relevance.