How to Unit Test your Forms

Caution

This article is intended for developers who create custom form types. If you are using the built-in Symfony form types or the form types provided by third-party bundles, you don't need to unit test them.

The Form component consists of 3 core objects: a form type (implementing FormTypeInterface), the Form and the FormView.

The only class that is usually manipulated by programmers is the form type class which serves as a form blueprint. It is used to generate the Form and the FormView. You could test it directly by mocking its interactions with the factory but it would be complex. It is better to pass it to FormFactory like it is done in a real application. It is easier to bootstrap and you can trust the Symfony components enough to use them as a testing base.

There is already a class that you can benefit from for testing: TypeTestCase. It is used to test the core types and you can use it to test your types too.

Note

Depending on the way you installed your Symfony or Symfony Form component the tests may not be downloaded. Use the --prefer-source option with Composer if this is the case.

The Basics

The simplest TypeTestCase implementation looks like the following:

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        // tests/Form/Type/TestedTypeTest.php
namespace App\Tests\Form\Type;

use App\Form\Type\TestedType;
use App\Model\TestObject;
use Symfony\Component\Form\Test\TypeTestCase;

class TestedTypeTest extends TypeTestCase
{
    public function testSubmitValidData(): void
    {
        $formData = [
            'test' => 'test',
            'test2' => 'test2',
        ];

        $model = new TestObject();
        // $model will retrieve data from the form submission; pass it as the second argument
        $form = $this->factory->create(TestedType::class, $model);

        $expected = new TestObject();
        // ...populate $expected properties with the data stored in $formData

        // submit the data to the form directly
        $form->submit($formData);

        // This check ensures there are no transformation failures
        $this->assertTrue($form->isSynchronized());

        // check that $model was modified as expected when the form was submitted
        $this->assertEquals($expected, $model);
    }

    public function testCustomFormView(): void
    {
        $formData = new TestObject();
        // ... prepare the data as you need

        // The initial data may be used to compute custom view variables
        $view = $this->factory->create(TestedType::class, $formData)
            ->createView();

        $this->assertArrayHasKey('custom_var', $view->vars);
        $this->assertSame('expected value', $view->vars['custom_var']);
    }
}
    

So, what does it test? Here comes a detailed explanation.

First you verify if the FormType compiles. This includes basic class inheritance, the buildForm() method and options resolution. This should be the first test you write:

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        $form = $this->factory->create(TestedType::class, $formData);
    

This test checks that none of your data transformers used by the form produces an error. The isSynchronized() method is only set to false if a data transformer throws an exception:

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        $form->submit($formData);
$this->assertTrue($form->isSynchronized());
    

Note

Don't test the validation: it is applied by a listener that is not active in the test case and it relies on validation configuration. Instead, unit test your custom constraints directly or read how to add custom extensions in the last section of this page.

Next, verify the submission and mapping of the form. The test below checks if all the fields are correctly specified:

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        $this->assertEquals($expected, $formData);
    

Finally, check the creation of the FormView. You can check that a custom variable exists and will be available in your form themes:

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        $this->assertArrayHasKey('custom_var', $view->vars);
$this->assertSame('expected value', $view->vars['custom_var']);
    

Tip

Use PHPUnit data providers to test multiple form conditions using the same test code.

Caution

When your type relies on the EntityType, you should register the DoctrineOrmExtension, which will need to mock the ManagerRegistry.

However, If you cannot use a mock to write your test, you should extend the KernelTestCase instead and use the form.factory service to create the form.

Testing Types Registered as Services

Your form may be used as a service, as it depends on other services (e.g. the Doctrine entity manager). In these cases, using the above code won't work, as the Form component instantiates the form type without passing any arguments to the constructor.

To solve this, you have to mock the injected dependencies, instantiate your own form type and use the PreloadedExtension to make sure the FormRegistry uses the created instance:

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        // tests/Form/Type/TestedTypeTest.php
namespace App\Tests\Form\Type;

use App\Form\Type\TestedType;
use Doctrine\ORM\EntityManager;
use Symfony\Component\Form\PreloadedExtension;
use Symfony\Component\Form\Test\TypeTestCase;
// ...

class TestedTypeTest extends TypeTestCase
{
    private MockObject&EntityManager $entityManager;

    protected function setUp(): void
    {
        // mock any dependencies
        $this->entityManager = $this->createMock(EntityManager::class);

        parent::setUp();
    }

    protected function getExtensions(): array
    {
        // create a type instance with the mocked dependencies
        $type = new TestedType($this->entityManager);

        return [
            // register the type instances with the PreloadedExtension
            new PreloadedExtension([$type], []),
        ];
    }

    public function testSubmitValidData(): void
    {
        // ...

        // Instead of creating a new instance, the one created in
        // getExtensions() will be used.
        $form = $this->factory->create(TestedType::class, $formData);

        // ... your test
    }
}
    

Adding Custom Extensions

It often happens that you use some options that are added by form extensions. One of the cases may be the ValidatorExtension with its invalid_message option. The TypeTestCase only loads the core form extension, which means an InvalidOptionsException will be raised if you try to test a class that depends on other extensions. The getExtensions() method allows you to return a list of extensions to register:

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        // tests/Form/Type/TestedTypeTest.php
namespace App\Tests\Form\Type;

// ...
use Symfony\Component\Form\Extension\Validator\ValidatorExtension;
use Symfony\Component\Validator\Validation;

class TestedTypeTest extends TypeTestCase
{
    protected function getExtensions(): array
    {
        $validator = Validation::createValidator();

        // or if you also need to read constraints from annotations
        $validator = Validation::createValidatorBuilder()
            ->enableAttributeMapping()
            ->getValidator();

        return [
            new ValidatorExtension($validator),
        ];
    }

    // ... your tests
}
    

Note

By default only the CoreExtension is registered in tests. You can find other extensions from the Form component in the Symfony\Component\Form\Extension namespace.

It is also possible to load custom form types, form type extensions or type guessers using the getTypes(), getTypeExtensions() and getTypeGuessers() methods.

When testing the themes of your forms, consider making your test extend the FormLayoutTestCase class. This saves a lot of boilerplate and code duplication by implementing the FormIntegrationTestCase methods for you. All you need to do is to implement the getTemplatePaths(), the getTwigExtensions() and the getThemes() methods.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.

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