I think that this test may fail by two reasons: IsentropicFlow has not a gamma attribute, or gamma attribute does not take the value indicated in the constructor then fails.

If you erase the gamma attribute the code will not run, therefore is a mistake very easy to detect.

If gamma attribute does not take its value from the parameter, almost all tests in this module will fail.

Is this test case worth? Maybe, if you are doing TDD this test case may allow you to write a constructor with a parameter and store its value in a gamma attribute. But, even in this case, I prefer to think about what I want to do with that gamma value and write a test case to expose it.

Anyway, if you think that this test case is interesting, let it into the test module. A bad test case is better than no test cases. There is always time to erase test cases ;)