Fixed #32611 -- Prevented unecessary setup()/teardown() calls when using --bisect/--pair runtests options.

[cjerdonek]

https://code.djangoproject.com/ticket/32611

[felixxm]

@cjerdonek Thanks for this patch 👍 I have a question about the second commit. bisect_tests() and paired_tests() are not called by and don't call django_tests(), so moving logging from setup() to django_tests() removes the initial "Testing against ..." output when test_labels are not provided, which is fine, IMO. Am I right? The ticket description suggests that you wanted to keep this output, that's why I'm asking.

[cjerdonek]

Good question, @felixxm. Thanks for asking. Once I started working on this, I noticed that a consequence of only calling setup() when test_labels isn't provided is that the initial logging would be different depending on whether test_labels is or isn't provided, which wouldn't be ideal. But then I realized that that initial logging isn't actually important for bisect_tests() and paired_tests() because that log message gets repeated when they each call the subprocess anyways (which will happen multiple times). So I thought it would be better just to do the call when the tests are actually being run (in the same process), instead of having the message duplicated by the parent process.

[felixxm]

So I thought it would be better just to do the call when the tests are actually being run (in the same process), instead of having the message duplicated by the parent process.

Agreed, thanks 👍