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, refer to library documentation and code examples for more information:

• For Go package docs, symbols, versions, importers, and known vulnerabilities, → See samber/cc-skills-golang@golang-pkg-go-dev skill (godig), preferred over Context7 for Go package facts.
• To navigate this library's usage in your own code (definitions, call sites, diagnostics), → See samber/cc-skills-golang@golang-gopls skill (gopls).
• Context7 remains a fallback for docs not indexed on pkg.go.dev.

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:

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

is := assert.New(t)