.. highlightlang:: python

simple patterns using hooks
==========================================================

pass different values to a test function, depending on command line options
----------------------------------------------------------------------------

Suppose we want to write a test that depends on a command line option.
Here is a basic pattern how to achieve this::

    # content of test_sample.py
    def test_answer(cmdopt):
        if cmdopt == "type1":
            print ("first")
        elif cmdopt == "type2":
            print ("second")
        assert 0 # to see what was printed


For this to work we need to add a command line option and
provide the ``cmdopt`` through a function argument factory::

    # content of conftest.py
    def pytest_addoption(parser):
        parser.addoption("--cmdopt", action="store", default="type1",
            help="my option: type1 or type2")

    def pytest_funcarg__cmdopt(request):
        return request.config.option.cmdopt

Let's run this without supplying our new command line option::

    $ py.test -q
    F
    ================================= FAILURES =================================
    _______________________________ test_answer ________________________________
    
    cmdopt = 'type1'
    
        def test_answer(cmdopt):
            if cmdopt == "type1":
                print ("first")
            elif cmdopt == "type2":
                print ("second")
    >       assert 0 # to see what was printed
    E       assert 0
    
    test_sample.py:6: AssertionError
    ----------------------------- Captured stdout ------------------------------
    first
    1 failed in 0.02 seconds

And now with supplying a command line option::

    $ py.test -q --cmdopt=type2
    F
    ================================= FAILURES =================================
    _______________________________ test_answer ________________________________
    
    cmdopt = 'type2'
    
        def test_answer(cmdopt):
            if cmdopt == "type1":
                print ("first")
            elif cmdopt == "type2":
                print ("second")
    >       assert 0 # to see what was printed
    E       assert 0
    
    test_sample.py:6: AssertionError
    ----------------------------- Captured stdout ------------------------------
    second
    1 failed in 0.02 seconds

Ok, this completes the basic pattern.  However, one often rather
wants to process command line options outside of the test and
rather pass in different or more complex objects.  See the
next example or refer to :ref:`mysetup` for more information
on real-life examples.

generating parameters combinations, depending on command line
----------------------------------------------------------------------------

Let's say we want to execute a test with different parameters
and the parameter range shall be determined by a command
line argument.  Let's first write a simple computation test::

    # content of test_compute.py

    def test_compute(param1):
        assert param1 < 4

Now we add a test configuration like this::

    # content of conftest.py

    def pytest_addoption(parser):
        parser.addoption("--all", action="store_true",
            help="run all combinations")

    def pytest_generate_tests(metafunc):
        if 'param1' in metafunc.funcargnames:
            if metafunc.config.option.all:
                end = 5
            else:
                end = 2
            for i in range(end):
                metafunc.addcall(funcargs={'param1': i})

This means that we only run 2 tests if we do not pass ``--all``::

    $ py.test -q test_compute.py
    ..
    2 passed in 0.01 seconds

We run only two computations, so we see two dots.
let's run the full monty::

    $ py.test -q --all test_compute.py
    ....F
    ================================= FAILURES =================================
    _____________________________ test_compute[4] ______________________________
    
    param1 = 4
    
        def test_compute(param1):
    >       assert param1 < 4
    E       assert 4 < 4
    
    test_compute.py:3: AssertionError
    1 failed, 4 passed in 0.03 seconds

As expected when running the full range of ``param1`` values
we'll get an error on the last one.