def make_b_or_c_py(self) -> None:
        """Create b_or_c.py, used in a few of these tests."""
        # "b_or_c.py b" will run 6 lines.
        # "b_or_c.py c" will run 7 lines.
        # Together, they run 8 lines.
        self.make_file("b_or_c.py", """\
            import sys
            a = 2
            if sys.argv[1] == 'b':
                b = 4
            else:
                c = 6
                c2 = 7
            d = 8
            print('done')
            """)
Create b_or_c.py, used in a few of these tests.
tests/test_process.py