Create a new test case, similar to TestCase.
However the test is assumed to use no fixture, and test suites are automatically created on the fly and added to the root fixture, based
on the slash-separated portions of testpath.
If testpath includes the component "subprocess" anywhere in it, the test will be skipped by default, and only run if
explicitly required via the `-p` command-line option or trap_subprocess.
| testpath |
/-separated test case path name for the test. |
| test_func |
The test function to invoke for this test. |