public function testGetUniqueFields() { $uniqueFieldsReflection = new \ReflectionProperty('Magento\\Framework\\Model\\ResourceModel\\Db\\AbstractDb', '_uniqueFields'); $uniqueFieldsReflection->setAccessible(true); $uniqueFieldsReflection->setValue($this->_model, null); $this->assertEquals([], $this->_model->getUniqueFields()); }