feature symfony#4712 Provide full test example (ifdattic)

This PR was merged into the 2.3 branch.

Discussion
----------

Provide full test example

In my opinion providing the full code for the example only adds a few additional lines, but increases the value of the example greatly.

Of course the name for the test should probably be changed as couldn't think of a good one. ping @stof

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3
| Fixed tickets |

Commits
-------

9832e23 Update tests.rst
4df1fe1 Update tests.rst
d4907ca Update tests.rst
d4ab971 Provide full test example

Author: weaverryan

best_practices/tests.rst

@@ -30,25 +30,35 @@ A functional test can be as easy as this:
 
 .. code-block:: php
 
-    /** @dataProvider provideUrls */
-    public function testPageIsSuccessful($url)
-    {
-        $client = self::createClient();
-        $client->request('GET', $url);
+    // src/AppBundle/Tests/ApplicationAvailabilityFunctionalTest.php
+    namespace AppBundle\Tests;
 
-        $this->assertTrue($client->getResponse()->isSuccessful());
-    }
+    use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;
 
-    public function provideUrls()
+    class ApplicationAvailabilityFunctionalTest extends WebTestCase
     {
-        return array(
-            array('/'),
-            array('/posts'),
-            array('/post/fixture-post-1'),
-            array('/blog/category/fixture-category'),
-            array('/archives'),
-            // ...
-        );
+        /**
+         * @dataProvider urlProvider
+         */
+        public function testPageIsSuccessful($url)
+        {
+            $client = self::createClient();
+            $client->request('GET', $url);
+
+            $this->assertTrue($client->getResponse()->isSuccessful());
+        }
+
+        public function urlProvider()
+        {
+            return array(
+                array('/'),
+                array('/posts'),
+                array('/post/fixture-post-1'),
+                array('/blog/category/fixture-category'),
+                array('/archives'),
+                // ...
+            );
+        }
     }
 
 This code checks that all the given URLs load successfully, which means that