> If a test runs by first setting up its own test fixture, creating from scratch all the data it will be using as input, then that test is guaranteed to be isolated. It doesn’t matter what order you run the tests, the results will be exactly the same.
Completely backward. This definition requires isolation, rather than granting it.
In reality, you (or your test framework) provides the isolation by hobbling along, executing only one test at a time.
Kent Beck is smart because he proposes fixes that work in real life, as in environments with dumb code and undisciplined people.
I can very much recommend his latest book ”Tidy first?”. It’s extremely short and concise, and is perfect for a very light book club within any tech team.
What he wrote is basically "don't repeat in test X what you already tested in test X-1".
It's not as much composition as compounding, and can work quite well.
Let's say something takes 20 steps, and you want to test all 20.
Instead of this:
test 1:
do step 1, assert step 1
test 2:
do step 1, assert step 1
do step 2, assert step 2
test 3:
do step 1, assert step 1
do step 2, assert step 2
do step 3, assert step 3
...
you do this:
test 1:
do step 1, assert step 1
test 2:
do step 1
do step 2, assert step 2
test 3:
do step 1
do step 2
do step 3, assert step 3
...
This works well in certain situations, as it skips diplicated redundant testing. Requires some discipline so that tests don't drift away from each other.
As most things, it depends on what those steps are. Perhaps you only need that one final (integration) test instead of 20 intermediate unit ones.
I wonder if it would work do design something that was able to say
test 1:
do step 1, assert step 1
test 2:
requires: test 1
do step 2, assert step 2
test 3:
requires: test 2
do step 3, assert step 3
test 4:
requires: test 2
do step 3, assert step 3
If the assertion of each test doesn't change any state, that might make things easier to read. Though, given that I haven't spent much time pondering it, I expect it could have it's own problems.
But it could also do things like skip test 3 if tests 2 or 1 failed - because it knows about the relationship.
> If a test runs by first setting up its own test fixture, creating from scratch all the data it will be using as input, then that test is guaranteed to be isolated. It doesn’t matter what order you run the tests, the results will be exactly the same.
Completely backward. This definition requires isolation, rather than granting it.
In reality, you (or your test framework) provides the isolation by hobbling along, executing only one test at a time.
I had a test suite with thousands of tests. One way of running it was to take all the passing tests, and then run them repeatedly in random order.
This found new bugs involving unintended persistent state.
I'm done listening to smart people proposing fixes for my dumb code.
Either I'm not smart or disciplined enough to make it work, or my colleagues are not. Mostly both.
Kent Beck is smart because he proposes fixes that work in real life, as in environments with dumb code and undisciplined people.
I can very much recommend his latest book ”Tidy first?”. It’s extremely short and concise, and is perfect for a very light book club within any tech team.
I agree, both with your analysis of him and your review of "Tidy first?". We read and discussed it at work, and I enjoyed it a lot.
What he wrote is basically "don't repeat in test X what you already tested in test X-1".
It's not as much composition as compounding, and can work quite well.
Let's say something takes 20 steps, and you want to test all 20.
Instead of this:
you do this: This works well in certain situations, as it skips diplicated redundant testing. Requires some discipline so that tests don't drift away from each other.As most things, it depends on what those steps are. Perhaps you only need that one final (integration) test instead of 20 intermediate unit ones.
I wonder if it would work do design something that was able to say
If the assertion of each test doesn't change any state, that might make things easier to read. Though, given that I haven't spent much time pondering it, I expect it could have it's own problems.But it could also do things like skip test 3 if tests 2 or 1 failed - because it knows about the relationship.