/radar

Test Selection & Prioritization Strategy

Purpose: Cut CI time without throwing away signal. Read this when Radar runs in SELECT mode or when suites are too slow to run fully on every change.

Contents:

• changed-file selection
• priority tiers
• incremental gates
• monorepo patterns
• skip conditions

Changed-File Based Selection

Vitest

npx vitest --changed HEAD~1
npx vitest --related src/utils/auth.ts
npx vitest --changed

Jest

npx jest --findRelatedTests src/utils/auth.ts src/services/user.ts
npx jest --changedSince=main
npx jest --onlyFailures
npx jest --changedSince=main --onlyFailures

pytest

pip install pytest-testmon
pytest --testmon
pytest --testmon --cov=src
pytest $(git diff --name-only main -- '*.py' | xargs -I{} dirname {} | sort -u)

Go

CHANGED_PKGS=$(git diff --name-only main -- '*.go' | xargs -I{} dirname {} | sort -u | sed 's|^|./|')
go test $CHANGED_PKGS
go test ./pkg/auth/...

Rust

cargo nextest run -p my-crate
cargo nextest run --partition count:1/4
cargo nextest run -E 'test(auth::)'
cargo nextest run --run-ignored=only

Fail-Likely-First Prioritization

Run P0 -> P1 -> P2 before you consider skipping a risky merge.

Incremental Execution Pipeline

3-Gate Strategy

Related CI planning from the broader test-DX perspective:

• Gate 1: lint + type check < 1min
• Gate 2: affected unit tests < 3min
• Gate 3: affected integration tests < 5min

Use the stricter gate when the pipeline already supports it.

Retry And Re-Run Rules

Retries are allowed only to surface flakes, not to hide real failures.

- name: Run tests with retry
  uses: nick-fields/retry@v3
  with:
    timeout_minutes: 10
    max_attempts: 3
    retry_on: error
    command: npx vitest run --reporter=junit --outputFile=test-results.xml

npx vitest run --retry 2

CI-Specific Patterns

Monorepo Patterns

Turborepo

npx turbo run test --filter=...[origin/main]
npx turbo run test --filter=@myorg/auth...
npx turbo run test --filter=...[origin/main] --dry-run

pnpm Workspace

pnpm --filter "...[origin/main]" run test
pnpm --filter @myorg/auth run test
pnpm -r --parallel run test

Nx

npx nx affected --target=test --base=main
npx nx run-many --target=test --projects=auth,users
npx nx affected:graph --base=main

Skip Conditions

Safe skip candidates:

• docs-only changes
• pure asset changes with no executable code impact
• config changes that provably cannot affect runtime behavior

Unsafe skip candidates:

• schema changes
• dependency upgrades
• shared library changes
• test utilities or global setup changes

Example:

if echo "$CHANGED" | grep -qvE '\\.(md|txt|png|jpg|svg|yml|yaml)$'; then
  echo "skip=false" >> $GITHUB_OUTPUT
else
  echo "skip=true" >> $GITHUB_OUTPUT
fi

Decision Rule

Use the smallest selection strategy that still covers:

1. last failures
2. directly changed behavior
3. high-value dependents
4. integration contracts touched by the change

If that still exceeds the budget, optimize sharding or caching before weakening the gate.

Quick Reference