def test_pth_and_source_work_together(self, dashm: str, package: str, source: str) -> None:
        """Run the test for a particular combination of factors.

        The arguments are all strings:

        * `dashm`: Either "" (run the program as a file) or "-m" (run the
          program as a module).

        * `package`: Either "" (put the source at the top level) or a
          package name to use to hold the source.

        * `source`: Either "main" or "sub", which file to use as the
          ``--source`` argument.

        """
        def fullname(modname: str) -> str:
            """What is the full module name for `modname` for this test?"""
            if package and dashm:
                return '.'.join((package, modname))
            else:
                return modname

        def path(basename: str) -> str:
            """Where should `basename` be created for this test?"""
            return os.path.join(package, basename)

        # Main will run sub.py.
        self.make_file(path("main.py"), """\
            import %s
            a = 2
            b = 3
            """ % fullname('sub'))
        if package:
            self.make_file(path("__init__.py"), "")
        # sub.py will write a few lines.
        self.make_file(path("sub.py"), """\
            f = open("out.txt", "w", encoding="utf-8")
            f.write("Hello, world!")
            f.close()
            """)
        self.make_file("coverage.ini", """\
            [run]
            source = %s
            """ % fullname(source))

        self.set_environ("COVERAGE_PROCESS_START", "coverage.ini")

        if dashm:
            cmd = "python -m %s" % fullname('main')
        else:
            cmd = "python %s" % path('main.py')

        self.run_command(cmd)

        with open("out.txt", encoding="utf-8") as f:
            assert f.read() == "Hello, world!"

        # Read the data from .coverage
        self.assert_exists(".coverage")
        data = coverage.CoverageData()
        data.read()
        summary = line_counts(data)
        assert summary[source + '.py'] == 3
        assert len(summary) == 1
Run the test for a particular combination of factors.

        The arguments are all strings:

        * `dashm`: Either "" (run the program as a file) or "-m" (run the
          program as a module).

        * `package`: Either "" (put the source at the top level) or a
          package name to use to hold the source.

        * `source`: Either "main" or "sub", which file to use as the
          ``--source`` argument.

        
tests/test_process.py