Test Runner Tips: Speed Up Your CI Pipeline

Test Runner Tips: Speed Up Your CI Pipeline

1) Parallelize and shard tests

• Split by file or suite across worker processes (runner flags like –maxWorkers, –jobs) and across CI jobs (shards).
• Shard deterministically (by file path hash) so reruns target the same subset.

2) Run only relevant tests

• Test impact analysis: run tests that cover changed files using dependency maps or tools (v8 test-coverage mapping, Jest’s changedFiles, Bazel/Gradle incremental).
• Fast pre-merge checks: run smoke/unit tests on PRs; run full integration/E2E on merge or nightly.

3) Cache and reuse artifacts

• Cache node_modules / virtualenv / compiled outputs and restore between CI jobs.
• Persist test build artifacts (compiled bundles, WebDriver binaries) to avoid repeated setup.