def test_compiler_check_flags_order(self):
        '''
        Test that compiler check flags override all other flags. This can't be
        an ordinary test case because it needs the environment to be set.
        '''
        testdir = os.path.join(self.common_test_dir, '36 has function')
        env = get_fake_env(testdir, self.builddir, self.prefix)
        cpp = detect_cpp_compiler(env, MachineChoice.HOST)
        Oflag = '-O3'
        OflagCPP = Oflag
        if cpp.get_id() in ('clang', 'gcc'):
            # prevent developers from adding "int main(int argc, char **argv)"
            # to small Meson checks unless these parameters are actually used
            OflagCPP += ' -Werror=unused-parameter'
        env = {'CFLAGS': Oflag,
               'CXXFLAGS': OflagCPP}
        self.init(testdir, override_envvars=env)
        cmds = self.get_meson_log_compiler_checks()
        for cmd in cmds:
            if cmd[0] == 'ccache':
                cmd = cmd[1:]
            # Verify that -I flags from the `args` kwarg are first
            # This is set in the '36 has function' test case
            self.assertEqual(cmd[1], '-I/tmp')
            # Verify that -O3 set via the environment is overridden by -O0
            Oargs = [arg for arg in cmd if arg.startswith('-O')]
            self.assertEqual(Oargs, [Oflag, '-O0'])

        Test that compiler check flags override all other flags. This can't be
        an ordinary test case because it needs the environment to be set.
        
unittests/linuxliketests.py