Go Unit Test Builder

Golang testing

by HoangNguyen0403 · MIT license · ★ 569 on GitHub

Write unit tests with table-driven patterns and interface mocking in Go. Use when writing Go unit tests, table-driven tests, or using mock interfaces.

---
name: golang-testing
description: Write unit tests with table-driven patterns and interface mocking in Go. Use when writing Go unit tests, table-driven tests, or using mock interfaces.
metadata:
  triggers:
    files:
    - '**/*_test.go'
    keywords:
    - testing
    - unit tests
    - go test
    - mocking
    - testify
---
# Golang Testing

## **Priority: P0 (CRITICAL)**

Overview

Write unit tests with table-driven patterns and interface mocking in Go. Use when writing Go unit tests, table-driven tests, or using mock interfaces.

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Golang Testing

Priority: P0 (CRITICAL)

Core Rule Anchors

[BE-TEST-01] Table-Driven Subtests for Equivalent Cases: Prefer table-driven tests ([]struct{ name, input, expected, expectErr } with t.Run) when functions have multiple equivalent inputs, boundary permutations, or repetitive setup. Distinct scenarios or diverging setup may remain separate test functions; 2-3 distinct cases are fine. Reviewers must not raise stylistic table-driven findings without a behavioral gap.
[BE-TEST-02] Ban on Brittle SQLMock String Matching: Do not use sqlmock.ExpectQuery to regex-match raw SQL strings. Test pure domain business calculations directly, or use testcontainers-go for PostgreSQL repository verification.
[BE-TEST-03] Ban on Shallow Assertions: Never assert only assert.NoError(t, err) or assert.NotNil(t, result) without inspecting returned domain struct fields, status codes, and invariants.
[BE-TEST-04] Ban on Pass-Through Interface Mocks: Repositories and service handlers must test contract compliance and error mapping. Ban 1:1 pass-through mock echoing without contract assertions.
[BE-TEST-05] Bug-First Regression Lock: Every PR fixing a bug ticket or with title fix(...) must introduce a test reproducing the defect prior to the fix.

Implementation Workflow

Write failing test first — Follow Red-Green-Refactor TDD workflow ([BE-TEST-05]).
Table-driven tests for equivalent inputs — For parameterized cases sharing setup, define test cases as a slice of structs with t.Run ([BE-TEST-01]).
Zero Volatile Fields for Struct Comparison — When asserting struct equality, zero out timestamps, dynamic IDs, or generated tokens before assert.Equal to prevent flaky assertions.
Mock via interfaces — Use DI and small, consumer-centric interfaces (1-3 methods) ([BE-TEST-04]). Prefer mockery for auto-generated mocks or manual mocks for simple cases.
Run parallel — Use t.Parallel() for non-sequential tests to speed up CI.
Clean up resources — Use t.Cleanup() to restore state or release DB/file resources.
Check coverage — Coverage is diagnostic and project-configured; verify risk-weighted critical paths rather than padding code for an arbitrary percentage.

See table-driven test examples

Tools & Naming

Stdlib: testing package (TestXxx(t *testing.T), ExampleXxx()).
Testify: Assertions (assert, require) and mocks.
Mockery / GoMock: Auto-generate mocks for interfaces.
Integration: Prefer testcontainers-go over raw SQL mock strings ([BE-TEST-02]).

Anti-Patterns

[BE-TEST-01] No stylistic rewrites: Do not demand table-driven rewrites of passing tests unless 5+ repetitive blocks or a coverage gap exists.
[BE-TEST-02] No raw SQL regex matching: Do not match SQL strings in mocks.
[BE-TEST-03] No shallow assertions: Never assert only assert.NoError/NotNil without payload inspection.
[BE-TEST-04] No pass-through mock echoing: Ban 1:1 mock echoing without contract assertions.
[BE-TEST-05] No bug fix without reproduction test.
No assert in loops: use t.Run subtests to isolate failures.
No brittle assertions on volatile fields: normalize timestamps/dynamic IDs.
No global mock state: define mocks locally within test scope.
No skipping race detection: always run go test -race in CI.

References

1	---
2	name: golang-testing
3	description: Write unit tests with table-driven patterns and interface mocking in Go. Use when writing Go unit tests, table-driven tests, or using mock interfaces.
4	metadata:
5	triggers:
6	files:
7	- '*/_test.go'
8	keywords:
9	- testing
10	- unit tests
11	- go test
12	- mocking
13	- testify
14	---
15	# Golang Testing
16
17	## Priority: P0 (CRITICAL)
18
19	## Core Rule Anchors
20
21	- `[BE-TEST-01]` Table-Driven Subtests for Equivalent Cases: Prefer table-driven tests (`[]struct{ name, input, expected, expectErr }` with `t.Run`) when functions have multiple equivalent inputs, boundary permutations, or repetitive setup. Distinct scenarios or diverging setup may remain separate test functions; 2-3 distinct cases are fine. Reviewers must not raise stylistic table-driven findings without a behavioral gap.
22	- `[BE-TEST-02]` Ban on Brittle SQLMock String Matching: Do not use `sqlmock.ExpectQuery` to regex-match raw SQL strings. Test pure domain business calculations directly, or use `testcontainers-go` for PostgreSQL repository verification.
23	- `[BE-TEST-03]` Ban on Shallow Assertions: Never assert only `assert.NoError(t, err)` or `assert.NotNil(t, result)` without inspecting returned domain struct fields, status codes, and invariants.
24	- `[BE-TEST-04]` Ban on Pass-Through Interface Mocks: Repositories and service handlers must test contract compliance and error mapping. Ban 1:1 pass-through mock echoing without contract assertions.
25	- `[BE-TEST-05]` Bug-First Regression Lock: Every PR fixing a bug ticket or with title `fix(...)` must introduce a test reproducing the defect prior to the fix.
26
27	## Implementation Workflow
28
29	1. Write failing test first — Follow Red-Green-Refactor TDD workflow (`[BE-TEST-05]`).
30	2. Table-driven tests for equivalent inputs — For parameterized cases sharing setup, define test cases as a slice of structs with `t.Run` (`[BE-TEST-01]`).
31	3. Zero Volatile Fields for Struct Comparison — When asserting struct equality, zero out timestamps, dynamic IDs, or generated tokens before `assert.Equal` to prevent flaky assertions.
32	4. Mock via interfaces — Use DI and small, consumer-centric interfaces (1-3 methods) (`[BE-TEST-04]`). Prefer `mockery` for auto-generated mocks or manual mocks for simple cases.
33	5. Run parallel — Use `t.Parallel()` for non-sequential tests to speed up CI.
34	6. Clean up resources — Use `t.Cleanup()` to restore state or release DB/file resources.
35	7. Check coverage — Coverage is diagnostic and project-configured; verify risk-weighted critical paths rather than padding code for an arbitrary percentage.
36
37	See [table-driven test examples](references/table-driven-tests.md)
38
39	## Tools & Naming
40
41	- Stdlib: `testing` package (`TestXxx(t *testing.T)`, `ExampleXxx()`).
42	- Testify: Assertions (`assert`, `require`) and mocks.
43	- Mockery / GoMock: Auto-generate mocks for interfaces.
44	- Integration: Prefer `testcontainers-go` over raw SQL mock strings (`[BE-TEST-02]`).
45
46	## Anti-Patterns
47
48	- `[BE-TEST-01]` No stylistic rewrites: Do not demand table-driven rewrites of passing tests unless 5+ repetitive blocks or a coverage gap exists.
49	- `[BE-TEST-02]` No raw SQL regex matching: Do not match SQL strings in mocks.
50	- `[BE-TEST-03]` No shallow assertions: Never assert only `assert.NoError`/`NotNil` without payload inspection.
51	- `[BE-TEST-04]` No pass-through mock echoing: Ban 1:1 mock echoing without contract assertions.
52	- `[BE-TEST-05]` No bug fix without reproduction test.
53	- No assert in loops: use `t.Run` subtests to isolate failures.
54	- No brittle assertions on volatile fields: normalize timestamps/dynamic IDs.
55	- No global mock state: define mocks locally within test scope.
56	- No skipping race detection: always run `go test -race` in CI.
57
58	## References
59
60	- [Table-Driven Tests](references/table-driven-tests.md)
61	- [Mocking Strategies](references/mocking-strategies.md)
62