Within an NUnit script there are TestFixture modules that contain a number of Test modules, see the NUnit Assembly example below in Visual Studio:
Note that the Assembly is called SCTM_NUnit, the TestFixture is called NUnit_SCTM and it has a number of Tests underneath it.
If you attempt to execute this via SCTM and you assign the NUnit Assembly above to a Test in SCTM the complete Assembly will be executed.
After executing the complete Assembly it is possible to convert the test in SCTM to a test package which will then display the individual TestFixtures and Test in a hierachy. If however you wish to only execute a single Test from within a NUnit Assembly or TestFixture when executing a test in SCTM then you need to use some NUnit switches. The switch to use in this instance is the 'run' switch as this enables you to define a specific test to be executed.
See an example of the usage of this in SCTM below:
Note that when using the 'run' switch you define the Test in its hierachy e.g. Assembly.TestFixture.Test
You can find details of the other NUnit switches at the following link: