FixtureLifeCycle

Added in NUnit 3.13.

FixtureLifeCycleAttribute selects how NUnit constructs your fixture class:

  • LifeCycle.SingleInstance — one instance is created and shared by every test in the fixture. This matches the usual NUnit default when you do not use the attribute.
  • LifeCycle.InstancePerTestCase — a new instance is created for each test.

Place the attribute on a fixture class to control that class, or on the assembly to set a default for all fixtures in that assembly. A class-level attribute overrides an assembly-level default.

InstancePerTestCase is often combined with Parallelizable. With a separate instance per test, instance fields are not shared while tests run in parallel, which avoids a common source of interference and often makes thread safety for instance state easier—while still leaving you responsible for static state, shared singletons, and other resources outside the fixture instance.

Constructor

FixtureLifeCycleAttribute(LifeCycle lifeCycle)
Parameter Type Description
lifeCycle LifeCycle SingleInstance or InstancePerTestCase.

Properties

Property Type Description Default
LifeCycle LifeCycle Life cycle for the fixture or assembly. (from constructor)

Applies To

Test Methods Test Fixtures (Classes) Assembly
❌ ✅ ✅

Assembly-level settings can be overridden by a class-level attribute.

LifeCycle enumeration

Value Meaning
LifeCycle.SingleInstance A single instance is created and shared for all test cases. This is the default.
LifeCycle.InstancePerTestCase A new instance is created for each test case.

Notes

  • When using LifeCycle.InstancePerTestCase, the OneTimeSetUp and OneTimeTearDown methods must be static, and each are only called once. This is required so that the setup or teardown methods do not access instance fields or properties that are reset for every test.

  • When using LifeCycle.InstancePerTestCase, a class's constructor will be called before every test is executed and IDisposable test fixtures will be disposed after the test is finished.

  • SetUp and TearDown methods are called before and after every test.

  • The Order attribute is respected.

See Also