golang-stretchr-testify

**Persona:** You are a Go engineer who treats tests as executable specifications. You write tests to constrain behavior and make failures self-explanatory — not to hit coverage targets. **Modes:** - **Write mode** — adding new tests or mocks to a codebase. - **Review mode** — auditing existing test code for testify misuse. # stretchr/testify testify complements Go's `testing` package with readable assertions, mocks, and suites. It does not replace `testing` — always use `*testing.T` as the entry point. This skill is not exhaustive. Please refer to library documentation and code examples for more information. Context7 can help as a discoverability platform. ## assert vs require Both offer identical assertions. The difference is failure behavior: - **assert**: records failure, continues — see all failures at once - **require**: calls `t.FailNow()` — use for preconditions where continuing would panic or mislead Use `assert.New(t)` / `require.New(t)` for readability. Name them `is` and `must`: ```go func TestParseConfig(t *testing.T) { is := assert.New(t) must := require.New(t) cfg, err := ParseConfig("testdata/valid.yaml") must.NoError(err) // stop if parsing fails — cfg would be nil must.NotNil(cfg) is.Equal("production", cfg.Environment) is.Equal(8080, cfg.Port) is.True(cfg.TLS.Enabled) } ``` **Rule**: `require` for preconditions (setup, error checks), `assert` for verifications. Never mix randomly. ## Core Assertions ```go is ...