baphled/dotopencode/test-fixtures-go

Skill: test-fixtures-go

What I do

I provide expertise in generating realistic test data for Go using factory-go patterns and gofakeit. I specialise in the functional options pattern for flexible, composable, and type-safe test fixtures.

When to use me

• Creating realistic mock data for Go unit and integration tests.
• Implementing the functional options pattern for object builders.
• Need random but structured data (UUIDs, emails, names) in tests.
• DRYing up test setup code across multiple Go spec files.

Core principles

1. Realistic Data — Use gofakeit to generate data that mimics production values (valid emails, real-looking names).
2. Functional Options — Prefer func(*Type) options for builders to keep the API clean and extensible.
3. Type Safety — Ensure fixtures return the correct types and handle mandatory fields by default.
4. Minimal Setup — Fixtures should return a valid object with zero arguments; override only what's needed.

Patterns & examples

Functional Options Pattern (Recommended)

type User struct {
    ID        string
    Email     string
    FirstName string
    Role      string
}
 
func NewUser(opts ...func(*User)) *User {
    user := &User{
        ID:        gofakeit.UUID(),
        Email:     gofakeit.Email(),
        FirstName: gofakeit.FirstName(),
        Role:      "user",
    }
    for _, opt := range opts {
        opt(user)
    }
    return user
}
 
// Options
func WithEmail(e string) func(*User) { return func(u *User) { u.Email = e } }
func WithRole(r string) func(*User)  { return func(u *User) { u.Role = r } }
 
// Usage
admin := NewUser(WithRole("admin"))

Integration with Ginkgo

var _ = Describe("UserService", func() {
    var user *User
    
    BeforeEach(func() {
        user = NewUser(WithRole("admin"))
    })
    
    It("grants admin privileges", func() {
        Expect(user.Role).To(Equal("admin"))
    })
})

Anti-patterns to avoid

• ❌ Hardcoded Constants — Leads to "mystery guest" problems and fragile tests.
• ❌ Manual Struct Literals — Duplicates setup logic and makes adding fields painful.
• ❌ Over-complex Builders — If a fixture needs 10+ options, the struct likely needs refactoring.

KB Reference

~/vaults/baphled/3. Resources/Knowledge Base/AI Development System/Skills/Testing-BDD/Test Fixtures Go.md

Related skills

• test-fixtures - Universal patterns for test data.
• ginkgo-gomega - Go BDD testing framework.
• golang - Core Go language idioms.