assertOverriddenKeys example

  public function testOverrideData($data, $module_data, $setting_data) {
    // Set initial data.     $this->config->setData($data);

    // Check original data was set correctly.     $this->assertConfigDataEquals($data);

    // Save so that the original data is stored.     $this->config->save();
    $this->assertFalse($this->config->hasOverrides());
    $this->assertOverriddenKeys($data, []);

    // Set module override data and check value before and after save.     $this->config->setModuleOverride($module_data);
    $this->assertConfigDataEquals($module_data);
    $this->assertOverriddenKeys($data, $module_data);

    $this->config->save();
    $this->assertConfigDataEquals($module_data);
    $this->assertOverriddenKeys($data, $module_data);

    // Reset the module overrides.