fix: use $BATS_RUN_TMPDIR for $BATS_MOCK_TMPDIR

[KlfJoat]

Update $BATS_MOCK_TMPDIR to $BATS_RUN_TMPDIR instead of $BATS_TMPDIR

Observed Behavior

Re-running Bats tests that call bats-mock exhibit unusual behavior when not all mocks are used and unstub is not called on all programs.

I created a bats test file that used bats-mock and (admittedly) I didn't write the test properly and I didn't unstub one program correctly. IMO, bats-mock should be resilient against my mistakes.

The problem exhibits just running a test like the one below, using only bats (and bats helper) code.

#!/usr/bin/env bats
load "$BATS_TEST_DIRNAME/bats_helpers/bats-support/load"
load "$BATS_TEST_DIRNAME/bats_helpers/bats-assert/load"
load "$BATS_TEST_DIRNAME/bats_helpers/bats-mock/stub"
@test "quux" {
  # Verify that foo is stubbed
  stub foo ': echo "STUBBED"'
  run foo
  assert_success
  assert_output "STUBBED"

  # Verify that bar is stubbed
  stub bar \
    ': echo "STUBBED"' \
    ': exit 1'
  run bar
  assert_success
  assert_output "STUBBED"

  # Test the exit function
  # run bar
  # assert_failure 1
  # refute_output

  unstub foo
  # unstub bar
}

Repeatedly running this test will alternate between passing and failing.

Why?

It appears that bats-mock uses $BATS_TMPDIR under the hood as the mock location. The problem is, per https://bats-core.readthedocs.io/en/stable/writing-tests.html#special-variables , that is just $TMPDIR or /tmp.

Since bats-mock does not clean up after itself, the ${program}-stub-plan and ${program}-stub-run files (that were not unstubbed by my bad test writing) persist across runs, leading to the alternating behavior.

On the other hand, $BATS_RUN_TMPDIR (added in bats v1.2.1) is cleaned up (or not if bats --no-tempdir-cleanup is used) after each run... And reuse of that directory is actively avoided by bats's invocation of mktemp when creating $BATS_RUN_TMPDIR.

Testing

I wanted to add a test for this issue to bats-mock, however because the results change between instances of bats itself, I'm not sure how to write a bats or other test for the issue.

I have tested the change and the test code above succeeds on every run. While that's not desired behavior (ideally bats-mock would throw an error if a program is stubbed and not unstubbed), it's at least consistent behavior which to my mind is preferable to inconsistency.

All of my other tests that use bats-mock pass with these changes, as do the bats-mock/tests.

[pzeballos]

Thanks @KlfJoat ! we had it in our backlog to fix 🙌🏻