public List<String> listModules() {
        return new ArrayList<>(usedModules);
    }
@Test
    void testListModules() {
        ModuleMock y = new ModuleMock("y");
        ModuleMock z = new ModuleMock("z");
        manager.loadModule("y", y);
        manager.loadModule("z", z);
        manager.useModules("z", "y");

        assertThat(manager.listModules()).containsSequence("z", "y");
    }