How to create a Test class with parameters?

Question

Here is what the current test code looks like:

def do_simulation(speed):
    df = run_simulation(speed)

    # following is a lot of assert that checks the values in df
    assert df["X"].iloc[0] == 0
    assert df["Y"].iloc[-1] == 2
    assert ...
    ....

def test_simulation():
    do_simulation(100)
    do_simulation(200)

I want to convert the test code to a Test class:

class TestSimulation(object):

    def setup_class(cls):
        cls.df = run_simulation(100) # I want to change the speed parameter

    def test_1():
        "comment 1"
        assert self.df["X"].iloc[0] == 0

    def test_2():
        "comment 2"
        assert self.df["Y"].iloc[-1] == 2

I read the document of py.test, but I can't figure out how to run TestSimulation for speed in [100, 200, ...]. the setup_class() method can only have cls argument.

What I want is a Test class that:

call do_simulation() once, and store the result.
call all the test method to check the simulation result.
I can different parameters to do_simulation().

satoru · Accepted Answer · 2015-05-29 01:55:14Z

1

You can use a pytest fixture and parametrize it:

@pytest.fixture(
    scope='module', # so that it's reused in the module scope
    params=[100, 200]
)
def simulation(request):
    speed = request.param
    # create the simulation
    return df

class Test:

    def test1(self, simulation):
        ...

    def test2(self, simulation):
        ...

answered May 29, 2015 at 1:55

satoru

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1 Comment

HYRY Over a year ago

Thanks, do you know when py.test do the gc collection? Because the simulation results are very big. I don't have enough memory If it keeps all the results when params is very long.

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