Golang Testing

Go Testing

This skill is about writing tests that are reliable, readable, and useful as documentation.

When to activate

• Writing new tests for functions, packages, or APIs
• Refactoring tests for clarity and reduced flakiness
• Adding benchmarks or fuzz tests
• Stabilizing concurrent or time-dependent tests (testing/synctest)
• Improving coverage without gaming the metric

Core rules (high signal)

• Prefer table-driven tests for coverage and readability.
• Use t.Helper() and t.Cleanup() to keep failures actionable.
• Tests should be deterministic: prefer testing/synctest over time.Sleep when the code under test uses time primitives.
• Prefer fakes (in-memory implementations) over heavy mocks.
• Use t.Parallel() only when the test is truly isolated.
• Keep test data local and explicit; avoid hidden cross-test coupling.
• Do not add exported production APIs solely for tests; prefer package seams, interfaces, or local fakes.
• Pair with test-driven-development when implementing persistent code or bug fixes test-first.
• Pair with testing-reliability for mock/timing anti-patterns and systematic-debugging when failure attribution is unclear.

Outcome expectations

• Unit tests are fast, deterministic, and easy to debug.
• Flaky tests are triaged with a repeatable reproduction loop.
• Bench/fuzz/coverage are used as correctness signals, not vanity metrics.

Recommended workflow

1. Write/adjust focused unit tests first (table + subtests).
2. Run targeted test selection to confirm behavior quickly.
3. Add race detector and coverage checks.
4. For instability, reproduce with repeated runs (-count) and isolate state/time dependencies (synctest for time-based concurrency).
5. Add benchmarks/fuzz tests when behavior or performance risk justifies them.

Quick checklist for a review

• Setup is outside the assertion loop; minimal shared mutable state
• Subtests have meaningful names (t.Run("case", ...))
• Error messages show got/want and context
• External dependencies are explicit (DBs, network, time)
• Benchmarks report allocs when relevant (b.ReportAllocs())

Resources

Load on demand:

• references/unit-tests.md — TDD loop, table tests, subtests, parallel subtests
• references/helpers-fixtures.md — helpers, TempDir, Cleanup, testdata, golden files
• references/mocking-fakes.md — interfaces for dependencies, fakes vs mocks, examples
• references/http-testing.md — httptest patterns, NewTestServer (Go 1.27+), JSON assertions
• references/bench-fuzz.md — benchmarks and fuzzing best practices
• references/fuzzing-and-race.md — load for go test -fuzz campaigns, race detector, goleak, goroutineleak profiles, and testing/synctest (Test/Wait/Sleep)
• references/coverage-ci.md — cover profiles, coverpkg notes, CI integration cautions
• references/commands.md — go test command recipes (race, timeout, count, patterns)