Allow for unit tests without decorators

[chusloj]

This PR addresses a problem that @jdebacker had with creating unit tests for calcfunctions.py without decorators (#2489).

Using pytest with functions in calcfunctions.py is possible if the iterate_jit decorator is removed, so the decorator will now simply return the passed function with no wrapper if the OS environment variable for TESTING is set to 'True' (as a string, the environment variable only accepts strings) in test_calcfunctions.py.

The test function test_DependentCare() provided in #2489 passes with this change.

---

This also enables unit testing discussed in #2419.

[jdebacker]

Love this - thanks @chusloj !

[chusloj]

@jdebacker,

I've found that changing the TESTING environment variable in test_calcfunctions.py apparently changes the variable for the entire test suite which causes problems. I've used monkeypatch to change the environment variable for that single function, but this means that any unit test made for calcfunctions.py will need a monkeypatch to change the environment variable. See below.

[hdoupe]

@chusloj this is really elegant! One thing to make it easier is adding a fixture that does monkeypatch.setenv("TESTING", "True")

import pytest

@pytest.fixture
def skip_jit(monkeypatch):
    monkeypatch.setenv("TESTING", "True")
    yield

def test_DependentCare(skip_jit):
    """
    Tests the DependentCare function
    """
    test_tuple = (3, 2, 100000, 1, [250000, 500000, 250000, 500000, 250000], 
                  .2, 7165, 5000, 0)
    test_value = calcfunctions.DependentCare(*test_tuple)
    expected_value = 25196

    assert np.allclose(test_value, expected_value)

The skip_jit function would go into conftest.py.

[chusloj]

@hdoupe Thanks very much for that suggestion! I was wondering how to fit the monkeypatch into a fixture but couldn't find the docs for how to implement a temporary change to a function using a fixture.

[hdoupe]

No problem @chusloj!

[MattHJensen]

Thanks for improving our testing capabilities, @chusloj! Merging now.