minor #9413 Add a 2nd argument to create() (ismail1432)

This PR was submitted for the 4.0 branch but it was squashed and merged into the 2.7 branch instead (closes #9413).

Discussion
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Add a 2nd argument to create()

Maybe I'm wrong but I tried the exemple with my case and the test failed because IMO if we don't pass an object to second argument, $form->getData() will return an array and this->assertEquals() can't compare an object with an array.
What do you think :-)

Commits
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ecef1fc Add a 2nd argument to create()

Author: javiereguiluz

form/unit_testing.rst

@@ -52,17 +52,19 @@ The simplest ``TypeTestCase`` implementation looks like the following::
                 'test2' => 'test2',
             );
 
-            $type = new TestedType();
-            $form = $this->factory->create($type);
+            $objectToCompare = new TestObject();
+            // $objectToCompare will retrieve data from the form submission; pass it as the second argument
+            $form = $this->factory->create(TestedType::class, $objectToCompare);
 
             $object = new TestObject();
             // ...populate $object properties with the data stored in $formData
 
             // submit the data to the form directly
             $form->submit($formData);
 
+            $objectToCompare = $form->getData();
             $this->assertTrue($form->isSynchronized());
-            $this->assertEquals($object, $form->getData());
+            $this->assertEquals($object, $objectToCompare);
 
             $view = $form->createView();
             $children = $view->children;
@@ -79,8 +81,7 @@ First you verify if the ``FormType`` compiles. This includes basic class
 inheritance, the ``buildForm()`` function and options resolution. This should
 be the first test you write::
 
-    $type = new TestedType();
-    $form = $this->factory->create($type);
+    $form = $this->factory->create(TestedType::class, $objectToCompare);
 
 This test checks that none of your data transformers used by the form
 failed. The :method:`Symfony\\Component\\Form\\FormInterface::isSynchronized`
@@ -98,7 +99,7 @@ method is only set to ``false`` if a data transformer throws an exception::
 Next, verify the submission and mapping of the form. The test below
 checks if all the fields are correctly specified::
 
-    $this->assertEquals($object, $form->getData());
+    $this->assertEquals($object, $objectToCompare);
 
 Finally, check the creation of the ``FormView``. You should check if all
 widgets you want to display are available in the children property::