Add pyroapi.tests module with example usage

[fritzo]

Addresses #2

This adds an importable module pyroapi.tests that depends on pytest. I expect this to eventually be similar to test_valid_models.py. We can later split this into pyroapi.tests.cheap and pyroapi.tests.expensive if needed. I've added an example conftest.py and test_tests.py do demonstrate use of pyroapi.tests.

I am a little dissatisfied that pyroapi.tests depends on pytest, but I believe we can make this an optional dependency, only required for users who want to use that component.

I am very happy with the terse usage pattern. Results look nice for the one test I've added:

test/test_testing.py::test_optimizer[pyro-Adam-py] <- pyroapi/tests.py PASSED            [  6%]
test/test_testing.py::test_optimizer[pyro-Adam-jit] <- pyroapi/tests.py PASSED           [ 12%]
test/test_testing.py::test_optimizer[pyro-ClippedAdam-py] <- pyroapi/tests.py PASSED     [ 18%]
test/test_testing.py::test_optimizer[pyro-ClippedAdam-jit] <- pyroapi/tests.py PASSED    [ 25%]
test/test_testing.py::test_optimizer[minipyro-Adam-py] <- pyroapi/tests.py PASSED        [ 31%]
test/test_testing.py::test_optimizer[minipyro-Adam-jit] <- pyroapi/tests.py PASSED       [ 37%]
test/test_testing.py::test_optimizer[minipyro-ClippedAdam-py] <- pyroapi/tests.py XFAIL  [ 43%]
test/test_testing.py::test_optimizer[minipyro-ClippedAdam-jit] <- pyroapi/tests.py XFAIL [ 50%]
test/test_testing.py::test_optimizer[numpy-Adam-py] <- pyroapi/tests.py XFAIL            [ 56%]
test/test_testing.py::test_optimizer[numpy-Adam-jit] <- pyroapi/tests.py XFAIL           [ 62%]
test/test_testing.py::test_optimizer[numpy-ClippedAdam-py] <- pyroapi/tests.py XFAIL     [ 68%]
test/test_testing.py::test_optimizer[numpy-ClippedAdam-jit] <- pyroapi/tests.py XFAIL    [ 75%]
test/test_testing.py::test_optimizer[funsor-Adam-py] <- pyroapi/tests.py XFAIL           [ 81%]
test/test_testing.py::test_optimizer[funsor-Adam-jit] <- pyroapi/tests.py XFAIL          [ 87%]
test/test_testing.py::test_optimizer[funsor-ClippedAdam-py] <- pyroapi/tests.py XFAIL    [ 93%]
test/test_testing.py::test_optimizer[funsor-ClippedAdam-jit] <- pyroapi/tests.py XFAIL   [100%]

Tested

• added example usage of pyroapi.tests
• added a test consumer to funsor: Add test of pyro-api funsor#266

[fritzo]

this is more automatic than our old xfail_if_not_implemented()

[fritzo]

Note this backend arg must be provided by a user-defined fixture, as in the tests.

[neerajprad]

Looks great to me!

I am a little dissatisfied that pyroapi.tests depends on pytest, but I believe we can make this an optional dependency, only required for users who want to use that component.

I agree. For as long as the main module doesn't depend on tests, having a dependency on pytest is okay. I expect that most users of these cases (at least in the near term) will be internal users who are using pytest as their test runner, so it doesn't seem like a big deal.