This description of taxcalc testing procedure is written for a person who wants to contribute changes to taxcalc source code. It assumes that you have read the USA Tax-Calculator Contributor Guide and have cloned the central GitHub TPRU-India taxcalc repository to your GitHub account and to your local computer, and are familiar with how to prepare a pull request for consideration by the core development team. This document describes the testing procedure you should follow on your local computer before submitting a development branch as a pull request to the central taxcalc repository at GitHub.
Currently there are two phases of testing.
The first phase of testing checks the formatting of the Python code against the PEP8-like standard. Assuming you are in the top-level directory of the repository, do these tests either of these two ways:
cd taxcalc
pycodestyle .
or
pycodestyle taxcalc
No messages indicate the tests pass. Fix any errors. When you pass all these PEP8-like tests, proceed to the second phase of testing.
Run the second-phase of testing as follows at the command prompt in the taxcalc directory at the top of the repository directory tree:
cd taxcalc
pytest -n4
This will start executing a pytest suite containing many tests.
Depending on your computer, the execution time for this suite of tests
is roughly one minute. The -n4 option calls for using as many as
four CPU cores for parallel execution of the tests. If you want
sequential execution of the tests (which will take at least twice as
long to execute), simply omit the -n4 option.
If you are adding an enhancement that expands the capabilities of
taxcalc, then all the tests you can run should pass before you
submit a pull request containing the enhancement. In addition, it
would be highly desirable to add a test to the pytest suite, which is
located in the taxcalc/tests directory, that somehow checks that
your enhancement is working as you expect it to work.
On the other hand, if you think you have found a bug in the taxcalc source code, the first thing to do is add a test to the pytest suite that demonstrates how the source code produces an incorrect result (that is, the test fails because the result is incorrect). Then change the source code to fix the bug and demonstrate that the newly-added test, which used to fail, now passes.
After an enhancement or bug fix, you may be convinced that the new and
different second-phase test results are, in fact, correct. How do you
eliminate the test failures? For all but a few tests, simply edit the
appropriate taxcalc/tests/test_*.py file so that the test passes
when you rerun pytest.