copilot-tdd-harness tdd-patterns.instructions.md

Go TDD Patterns

Treat this file as the project-specific source of truth for TDD work in this repository.

Commands

• For Go changes under samples/fizzbuzz-go, run go test ./... from that directory.
• Run go build ./... from samples/fizzbuzz-go only when a build verification step is warranted.
• There is no root Go module for this repository.

Run the narrowest practical command first when validating a small change, but fall back to the configured full test command before ending substantial work.

File Layout

• Source files are Go files under the repository using *.go.
• Tests are package-local files named *_test.go.
• Prefer adding tests next to the production code they exercise.

Test Naming

• Name tests with the Go Test... prefix.
• Use the repository convention TestWhenCondition_ShouldExpectedOutcome.
• Keep each new TDD cycle to exactly one new test covering exactly one behavior.

Examples:

• TestWhenModeIsUnsupported_ShouldReturnErrorMode
• TestWhenTestsFail_ShouldBlock

Assertions

• Use the Go standard library testing package.
• Prefer t.Fatalf or t.Fatal with explicit expected/actual output.
• Keep assertion messages concrete and behavior-focused.

Stand-ins

• Prefer handwritten fakes or stubs behind small interfaces.
• Use standard library testing tools unless a strong reason exists to add a mock framework.
• Keep stand-ins local to the test package unless they are broadly reusable.

Repository Notes

• This repo now contains packaged harness assets plus sample Go code under samples/fizzbuzz-go.
• Validate Go changes in the owning sample module rather than from the repository root.