Quickstart

A first factory

package user_test

import (
  "testing"

  "github.com/Goldziher/fabricator/v2"
)

type User struct {
  ID    int
  Name  string
  Email string
  Admin bool
}

var (
  userID    = fabricator.FieldOf[User, int]("ID")
  userName  = fabricator.FieldOf[User, string]("Name")
  userAdmin = fabricator.FieldOf[User, bool]("Admin")
)

func userFactory() *fabricator.Factory[User] {
  return fabricator.New(User{},
    fabricator.Field(userID, func(ctx fabricator.BuildContext) int {
      return ctx.Iteration + 1
    }),
  )
}

New takes a zero value of the model — it is there to infer T, not to supply data. Field takes a provider that receives a BuildContext, whose Iteration counts builds from this factory starting at 0.

Build one

user := userFactory().Build()
// ID is 1. Name, Email, and Admin are generated.

Override per test

Build takes options that apply to that call only:

func TestAdminCanDelete(t *testing.T) {
  admin := userFactory().Build(fabricator.Override(userAdmin, true))
  // Admin is true. Everything else is still generated.
}

The test states the one thing it depends on. It keeps compiling and keeps passing when User grows a field.

Build many

factory := userFactory()
users := factory.Batch(3)
// IDs 1, 2, 3 — the counter advances once per build.

Batch applies its options to every instance, and providers still see each build’s own iteration:

users := factory.Batch(3, fabricator.Override(userName, "Moishe"))
// all named Moishe, IDs still 1, 2, 3

Cycle through values

role := fabricator.FieldOf[User, string]("Role")

factory := fabricator.New(User{},
  fabricator.Field(role, fabricator.Sequence("admin", "editor", "viewer")),
)

factory.Batch(5) // admin, editor, viewer, admin, editor

Handle errors instead of panicking

Build, Batch, Create, and CreateBatch panic on failure, which keeps test bodies terse. Each has an E twin that returns an error instead:

user, err := factory.BuildE()
users, err := factory.BatchE(10)

Exact fixtures

When a test asserts field by field, generated values in the fields it does not set are noise. WithoutFaker starts from the zero value:

factory := fabricator.New(User{},
  fabricator.WithoutFaker[User](),
  fabricator.Value(userName, "Moishe"),
)

factory.Build() // User{ID: 0, Name: "Moishe", Email: "", Admin: false}

Next

• Fields and values — every way to configure a field
• Factories from factories — Extend and subfactories
• Determinism — reproducing a failure