public function testClass()
{
$model = new User();
$this->assertFalse($model->isValid());
$this->assertTrue($model->hasErrors());
$this->assertTrue($model->hasErrors('username'));
$this->assertEquals(['username' => ['Cannot be empty', 'Minimal length is 3']], $model->getErrors());
$this->assertEquals(['Cannot be empty', 'Minimal length is 3'], $model->getErrors('username'));
$model->clearErrors('username');
$this->assertEquals([], $model->getErrors());
}