`test_chmod_ugoa` and `test_chmod_many_options` both change umask, which
is global state. Since tests run concurrently, this might lead to
a situation where one of the tests changes umask to a value that screws
another test's checks. To prevent this, we introduce a mutex that should
be held by any test that changes umask.
Unfortunately, there's no way to hide umask behind this mutex and
enforce its usage: programmers will have to maintain the discipline
themselves.
`test_chmod_many_options` relied on user's umask not denying read access
for anyone. 022, which is the default umask for many, indeed allows read
access for everyone. I'm using 027, which disallows read for everyone
but owner and group. This made tests fail.
Now tests set and reset umask, ensuring checks are run in a reliable,
predictable environment.
Updates to individual integration tests
- use proposed conventional approach to beginning tests
- use new convenience functions for using fixtures
- use new names for TestScenario
Updates to integration test modules
- add proposed conventional module-level functions
Updates to test/common/util.rs
- rename TestSet, and its methods, for semantic clarity
- create convenience functions for use of fixtures
- delete convenience functions obsoleted by new conventions
The main motivation is to move toward running those tests for a specific
target, that is, if a test won't run on Windows, then we shouldn't build
it. This was previously the default behavior and prevented a successful
run on AppVeyor.
I borrowed this pattern from the tests in the Cargo project.
