class TriggeringElementProgrammedTest

class TriggeringElementProgrammedTest extends KernelTestBase implements FormInterface {
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'triggering_element_programmed_form';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $form['one'] = [
            '#type' => 'textfield',
            '#title' => 'One',
            '#required' => TRUE,
        ];
        $form['two'] = [
            '#type' => 'textfield',
            '#title' => 'Two',
            '#required' => TRUE,
        ];
        $form['actions'] = [
            '#type' => 'actions',
        ];
        $user_input = $form_state->getUserInput();
        $form['actions']['submit'] = [
            '#type' => 'submit',
            '#value' => 'Save',
            '#limit_validation_errors' => [
                [
                    $user_input['section'],
                ],
            ],
            // Required for #limit_validation_errors.
'#submit' => [
                [
                    $this,
                    'submitForm',
                ],
            ],
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
        // Verify that the only submit button was recognized as triggering_element.
        $this->assertEquals($form['actions']['submit']['#array_parents'], $form_state->getTriggeringElement()['#array_parents']);
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
    }
    
    /**
     * Tests that #limit_validation_errors of the only submit button takes effect.
     */
    public function testLimitValidationErrors() {
        // Programmatically submit the form.
        $form_state = new FormState();
        $form_state->setValue('section', 'one');
        $form_builder = $this->container
            ->get('form_builder');
        $form_builder->submitForm($this, $form_state);
        // Verify that only the specified section was validated.
        $errors = $form_state->getErrors();
        $this->assertTrue(isset($errors['one']), "Section 'one' was validated.");
        $this->assertFalse(isset($errors['two']), "Section 'two' was not validated.");
        // Verify that there are only values for the specified section.
        $this->assertTrue($form_state->hasValue('one'), "Values for section 'one' found.");
        $this->assertFalse($form_state->hasValue('two'), "Values for section 'two' not found.");
    }

}