golang-stretchr-testify
Comprehensive guide to stretchr/testify for Golang testing. Covers assert, require, mock, and suite packages in depth. Use when writing tests with testify, creating mocks, setting up test suites, or choosing between assert and require. Covers testify assertions, mock expectations, argument matchers, call verification, suite lifecycle, and advanced patterns like Eventually, JSONEq, and custom matchers. Apply when the codebase imports github.com/stretchr/testify.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/samber/cc-skills-golang --skill golang-stretchr-testify- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads golang-stretchr-testify automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
Security audits
Independent scans of the skill's instructions and bundled files.
SKILL.md
The instructions your agent reads when the skill is triggered.
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-devskill (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-goplsskill (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)
// Equality
is.Equal(expected, actual) // DeepEqual + exact type
is.NotEqual(unexpected, actual)
is.EqualValues(expected, actual) // converts to common type first
is.EqualExportedValues(expected, actual)
// Nil / Bool / Emptiness
is.Nil(obj) is.NotNil(obj)
is.True(cond) is.False(cond)
is.Empty(collection) is.NotEmpty(collection)
is.Len(collection, n)
// Contains (strings, slices, map keys)
is.Contains("hello world", "world")
is.Contains([]int{1, 2, 3}, 2)
is.Contains(map[string]int{"a": 1}, "a")
// Comparison
is.Greater(actual, threshold) is.Less(actual, ceiling)
is.Positive(val) is.Negative(val)
is.Zero(val)
// Errors
is.Error(err) is.NoError(err)
is.ErrorIs(err, ErrNotFound) // walks error chain
is.ErrorAs(err, &target)
is.ErrorContains(err, "not found")
// Type
is.IsType(&User{}, obj)
is.Implements((*io.Reader)(nil), obj)
Argument order: always (expected, actual) — swapping produces confusing diff output.
Advanced Assertions
is.ElementsMatch([]string{"b", "a", "c"}, result) // unordered comparison
is.InDelta(3.14, computedPi, 0.01) // float tolerance
is.JSONEq(`{"name":"alice"}`, `{"name": "alice"}`) // ignores whitespace/key order
is.WithinDuration(expected, actual, 5*time.Second)
is.Regexp(`^user-[a-f0-9]+$`, userID)
// Async polling
is.Eventually(func() bool {
status, _ := client.GetJobStatus(jobID)
return status == "completed"
}, 5*time.Second, 100*time.Millisecond)
// Async polling with rich assertions
is.EventuallyWithT(func(c *assert.CollectT) {
resp, err := client.GetOrder(orderID)
assert.NoError(c, err)
assert.Equal(c, "shipped", resp.Status)
}, 10*time.Second, 500*time.Millisecond)
testify/mock
Mock interfaces to isolate the unit under test. Embed mock.Mock, implement methods with m.Called(), always verify with AssertExpectations(t).
Key matchers: mock.Anything, mock.AnythingOfType("T"), mock.MatchedBy(func). Call modifiers: .Once(), .Times(n), .Maybe(), .Run(func).
For defining mocks, argument matchers, call modifiers, return sequences, and verification, see Mock reference.
testify/suite
Suites group related tests with shared setup/teardown.
Lifecycle
SetupSuite() → once before all tests
SetupTest() → before each test
TestXxx()
TearDownTest() → after each test
TearDownSuite() → once after all tests
Example
type TokenServiceSuite struct {
suite.Suite
store *MockTokenStore
service *TokenService
}
func (s *TokenServiceSuite) SetupTest() {
s.store = new(MockTokenStore)
s.service = NewTokenService(s.store)
}
func (s *TokenServiceSuite) TestGenerate_ReturnsValidToken() {
s.store.On("Save", mock.Anything, mock.Anything).Return(nil)
token, err := s.service.Generate("user-42")
s.NoError(err)
s.NotEmpty(token)
s.store.AssertExpectations(s.T())
}
// Required launcher
func TestTokenServiceSuite(t *testing.T) {
suite.Run(t, new(TokenServiceSuite))
}
Suite methods like s.Equal() behave like assert. For require: s.Require().NotNil(obj).
Common Mistakes
- Forgetting
AssertExpectations(t)— mock expectations silently pass without verification is.Equal(ErrNotFound, err)— fails on wrapped errors. Useis.ErrorIsto walk the chain- Swapped argument order — testify assumes
(expected, actual). Swapping produces backwards diffs assertfor guards — test continues after failure and panics on nil dereference. Userequire- Missing
suite.Run()— without the launcher function, zero tests execute silently - Comparing pointers —
is.Equal(ptr1, ptr2)compares addresses. Dereference or useEqualExportedValues
Linters
Use testifylint to catch wrong argument order, assert/require misuse, and more. See samber/cc-skills-golang@golang-lint skill.
Cross-References
- → See
samber/cc-skills-golang@golang-testingskill for general test patterns, table-driven tests, and CI - → See
samber/cc-skills-golang@golang-lintskill for testifylint configuration
FAQ
What does the golang-stretchr-testify skill do?
Comprehensive guide to stretchr/testify for Golang testing. Covers assert, require, mock, and suite packages in depth. Use when writing tests with testify, creating mocks, setting up test suites, or choosing between assert and require. Covers testify assertions, mock expectations, argument matchers, call verification, suite lifecycle, and advanced patterns like Eventually, JSONEq, and custom matchers. Apply when the codebase imports github.com/stretchr/testify.
How do I install golang-stretchr-testify?
Run npx skills add https://github.com/samber/cc-skills-golang --skill golang-stretchr-testify in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/golang-stretchr-testify/ (personal) or .claude/skills/golang-stretchr-testify/ (project).
Which AI agents can use golang-stretchr-testify?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is golang-stretchr-testify safe to install?
Security partners have reviewed it: Gen Agent Trust Hub passed; Socket passed; Snyk passed; ZeroLeaks passed. As with any skill, read the SKILL.md and bundled scripts before installing.
Who maintains golang-stretchr-testify?
It is published by samber in samber/cc-skills-golang. It has 39,542 recorded installs.
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