[Notes] [Git][BuildStream/buildstream][aevri/unit

dcecd057

by Angelos Evripiotis at 2018-11-08T17:37:21Z

contributing: add guidance on unit tests

Decrease uncertainty around whether unit tests are welcome in the
project or not.

@@ -1525,6 +1525,24 @@ Tests that run a sandbox should be decorated with::
  and use the integration cli helper.
 +You should first aim to write tests that exercise your changes from the cli.
 +This is so that the testing is end-to-end, and the changes are guaranteed to
 +work for the end-user. The cli is considered stable, and so tests written in
 +terms of it are unlikely to require updating as the internals of the software
 +change over time.
++
 +It may be impractical to sufficiently examine some changes this way. For
 +example, the number of cases to test and the running time of each test may be
 +too high. It may also be difficult to contrive circumstances to cover every
 +line of the change. If this is the case, next you can consider also writing
 +unit tests that work more directly on the changes.
++
 +It is important to write unit tests in such a way that they do not break due to
 +changes unrelated to what they are meant to test. For example, if the test
 +relies on a lot of BuildStream internals, a large refactoring will likely
 +require the test to be rewritten. Pure functions that only rely on the Python
 +Standard Library are excellent candidates for unit testing.
++
  Measuring performance
  ---------------------

[Notes] [Git][BuildStream/buildstream][aevri/unit_tests] contributing: add guidance on unit tests