Parallelizable Attribute - jnm2/nunit-docs-wiki GitHub Wiki

This attribute is used to indicate whether the test and/or its descendants may be run in parallel with other tests. By default, no parallel execution takes place.

The constructor takes an optional ParallelScope enumeration argument (see below), which defaults to ParallelScope.Self. The attribute may be used at the assembly, class or method level and the word "test" in the rest of this description refers to the suite or test case that corresponds to the item on which the attribute appears.

This is a [Flags] enumeration used to specify which tests may run in parallel. It applies to the test upon which it appears and any subordinate tests. It is defined as follows:

[Flags]
public enum ParallelScope
{
    None,     // the test may not be run in parallel with other tests
    Self,     // the test itself may be run in parallel with other tests
    Children, // child tests may be run in parallel with one another
    Fixtures  // fixtures may be run in parallel with one another
}

1. Parallel execution of methods within a class is supported starting with NUnit 3.7. In earlier releases, parallel execution only applies down to the TestFixture level, ParallelScope.Children works as ParallelScope.Fixtures and any ParallelizableAttribute placed on a method is ignored.

2. Values that apply to a higher level test than the test on which the scope appears - for example, ParallelScope.Fixtures appearing on a method - are ignored without warning or affect.

3. Although ParallelScope.None continues to be supported, it is recommended that you use the new NonParallelizable Attribute in new work.

4. Parallel execution is supported by the NUnit framework on desktop .NET runtimes. It is not supported in our Portable or .NET Standard builds at this time, although the attributes are recognized without error in order to allow use in projects that build against multiple targets.

The ParallelizableAttribute may be specified on multiple levels of the tests. Settings at a higher level may affect lower level tests, unless those lower-level tests override the inherited settings. Thus, if the assembly has ParallelScope.None either by use of the attribute or by default, classes with ParallelScope.Self may be run in parallel as may their children if an appropriate scope is used.

Note that a lower-level test cannot change the settings on higher-level tests. Thus, allowing parallel execution for methods of a class that does not allow it, results in those methods running in parallel with one another, but not in parallel with test methods under any other classes. This is the natural outcome of the fact that the execution of a test method is, in fact, part of the execution of the test represented by the class.

• NonParallelizable Attribute
• LevelOfParallelism Attribute