pattern will
        be loaded. (Using shell style pattern matching.)

        All test modules must be importable from the top level of the project.
        If the start directory is not the top level directory then the top
        level directory must be specified separately.

        If a test package name (directory with '__init__.py') matches the
        pattern then the package will be checked for a 'load_tests' function. If
        this exists then it will be called with (loader, tests, pattern) unless
        the package has already had load_tests called from the same discovery
        invocation, in which case the package module object is not scanned for
        tests - this ensures that when a package uses discover to further
        discover child tests that infinite recursion does not happen.

        If load_tests exists then discovery does *not* recurse into the package,
        load_tests is responsible for loading all tests in the package.

        The pattern is deliberately not stored as a loader attribute so that
        packages can continue discovery themselves. top_level_dir is stored so
        load_tests does not need to pass this argument in to loader.discover().

        Paths are sorted before being imported to ensure reproducible execution
        order even on filesystems with non-alphabetical ordering like ext3/4.
        FNTr