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expecting you to use
List()
and
.save()
, you’ll get failing tests even though the actual
effect of the code would be the same. If you’re not careful, this can start to work against
one of the supposed benefits of having tests, which was to encourage refactoring. You
can find yourself having to change dozens of mocky tests and contract tests when you
want to change an internal API.
Notice that this may be more of a problem when you’re dealing with an API you don’t
control. You may remember the contortions we had to go through to test our form,
mocking out two Django model classes and using
side_effect
to check on the state of
the world. If you’re writing code that’s totally under your own control, you’re likely to
design your internal APIs so that they are cleaner and require less contortions to test.
But All These Problems Can Be Overcome
But, isolation advocates will come back and say, all that stuff can be mitigated, you just
need to get better at writing isolated tests, and, remember the holy flow state? The holy
flow state!
So where are we?
Synthesis: What Do We Want from Our Tests, Anyway?
Let’s step back and have a think about what benefits we want our tests to deliver. Why
are we writing them in the first place?
Correctness
We want our application to be free of bugs—both low-level logic errors, like off-by-one
errors, and high-level bugs like the software ultimately should deliver what our users
want. We want to find out if we ever introduce regressions which break something that
used to work, and we want to find that out before our users see something broken. We
expect our tests to tell us our application is correct.
Clean, Maintainable Code
We want our code to obey rules like “YAGNI” and “DRY”. We want code that clearly
expresses its intentions, which is broken up into sensible components that have well-
defined responsibilities and are easily understood. We expect our tests to give us the
confidence to refactor our application constantly, so that we’re never scared to try and
improve its design, and we would also like it if they would actively help us to find the
right design.
Synthesis: What Do We Want from Our Tests, Anyway?
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