Fixture and Create

Learn how Fixture.Create generates anonymous specimens for types you request.

Fixture is the main entry point. Call Create<T>() to get an anonymous instance of T.

Example scenario

You are testing code that needs a ClientDto with a name and age. The exact values do not matter — you only need a populated object for the arrange step.

Example

var fixture = new Fixture();

var number = fixture.Create<int>();
var text = fixture.Create<string>();
var dto = fixture.Create<ClientDto>();

Assert.NotEqual(default, number);
Assert.False(string.IsNullOrEmpty(text));
Assert.False(string.IsNullOrEmpty(dto.Name));

Use CreateMany<T>(count) when you need several values:

var values = fixture.CreateMany<int>(3).ToList();

Assert.Equal(3, values.Count);
Assert.True(values.Distinct().Count() > 1);

How it works

  • new Fixture() — starts a fresh generator for this test
  • Create<T>() — resolves T through AutoFixture's specimen pipeline (constructor, properties, nested types)
  • CreateMany<T>(count) — returns an enumerable of distinct anonymous values
  • Different each call — successive Create<T>() calls usually return different values, which helps avoid tests that pass only for one hard-coded number
  • Same value twice — use FromSeed in Customizations or Freeze in Register, Freeze, and Inject when a test needs repeatability or one shared instance

See also Collections.

Next steps

API

Refactoring a test

Build DSL