Merge pull request #2159 from Ragazzo/codeception_ext_docs_fix

Codeception ext docs fix

extensions/codeception/README.md

@@ -41,6 +41,11 @@ and application destroy after each test. You can configure a mock application us
 `TestCase` is extended from `Codeception\TestCase\Case` so all methods and assertions are available.
 You may use codeception modules and fire events in your test, just use methods:
 
+Getting Codeception modules
+---------------------------
+
+If you want to use codeception modules and helpers in your unit tests, you can do it like this:
+
 ```php
 <?php
 #in your unit-test
@@ -53,8 +58,10 @@ You also can use all guy methods by accessing guy instance like:
 <?php
 $this->codeGuy->someMethodFromModule();
 ```
+Codeception events
+------------------
 
-to fire event do this:
+To fire event do this:
 
 ```php
 <?php
@@ -68,6 +75,10 @@ public function testSomething()
 this event can be catched in modules and helpers. If your test is in the group, then event name will be followed by the groupname, 
 for example ```myevent.somegroup```.
 
+
+Special test method chaining
+----------------------------
+
 Execution of special tests methods is (for example on ```UserTest``` class):
 
 ```
@@ -88,49 +99,121 @@ tests\unit\models\UserTest::tearDownAfterClass();
 
 If you use special methods dont forget to call its parent.
 
+Customizing application config
+------------------------------
+
+You may need to specify different configuration files per test cases, to do this you can make it like the following:
+
 ```php
 <?php
 
 SomeConsoleTest extends \yii\codeception\TestCase
 {
 	// this is the config file to load as application config
-	public static $applicationConfig = '@app/config/web.php';
-
-	// this defines the application class to use for mock applications
-	protected $applicationClass = 'yii\web\Application';
+	public $appConfig = '@app/path/to/my/custom/config/for/test.php';
 }
 ```
 
-The `$applicationConfig` property may be set for all tests in a `_bootstrap.php` file like this:
+The `$appConfig` property could be an array or a valid alias, pointing to the file that returns a config array. You can specify
+application class in the config, for example for testing console commands or features you can create `_console.php` config under
+`tests/unit` directory like this:
 
 ```php
-<?php
-
-yii\codeception\TestCase::$applicationConfig = yii\helpers\ArrayHelper::merge(
-	require(__DIR__ . '/../../config/web.php'),
-	require(__DIR__ . '/../../config/codeception/unit.php')
+return yii\helpers\ArrayHelper::merge(
+	require(__DIR__ . '/../../config/console.php'),
+	require(__DIR__ . '/../_config.php'),
+	[
+		'class' => 'yii\console\Application',
+		'components' => [
+			//override console components if needed
+		],
+	]
 );
 ```
 
-Don't forget that you have to include autoload and Yii class in the `_bootstrap.php` file.
+and then just use your `ConsoleTestCase` like the following:
 
-You also can reconfigure some components for tests, for this purpose there is a `$config` property in the `TestCase` class.
+```php
+
+use \yii\codeception\TestCase;
+
+class ConsoleTestCase extends TestCase
+{
+	public $appConfig = '@tests/unit/_console.php';
+}
+```
+
+You can extend other console test cases from this basic `ConsoleTestCase`.
+
+Reconfiguring components for testing
+------------------------------------
+
+You can reconfigure a component for testing, for this purpose in your `setUp` method of your test case 
+you can do this for example:
 
 ```php
 <?php
 
-SomeOtherTest extends \yii\codeception\TestCase
+use \yii\codeception\TestCase;
+use Yii;
+
+class MailTest extends TestCase
 {
-	public $config = [
-		'components' => [
-			'mail' => [
-				'useFileTransport' => true,
-			],
-		]
-	];
+
+	protected function setUp()
+	{
+		// don't forget to call parent method that will setup Yii application
+		parent::setUp();
+
+		Yii::$app->mail->fileTransportCallback = function ($mailer, $message) {
+			return 'testing_message.eml';
+		};
+	}
+
 }
 ```
 
+You don't need to worry about application instances and isolation because application will be created [each time](https://github.com/yiisoft/yii2/blob/master/extensions/codeception/TestCase.php#L31) before any of test method will be executed in test case.
+You can mock application in a different way. For this purposes you have method [`mockApplication`](https://github.com/yiisoft/yii2/blob/master/extensions/codeception/TestCase.php#L55) available in your test case.
+This method creates new application instance and replaces old one with it and is handy when you need to create application with a config that is different from other test methods in the current test suite. For example:
+
+```php
+
+use \yii\codeception\TestCase;
+
+class SomeMyTest extends TestCase
+{
+
+	public function testOne()
+	{
+		...
+	}
+
+	public function testTwo()
+	{
+		$this->mockApplication([
+			'language' => 'ru-RU',
+			'components' => [
+				'db' => [
+					//your custom configuration here
+				],
+			],
+		]);
+
+		//your expectations and assertions goes here
+	}
+
+	public function testThree()
+	{
+		...
+	}
+
+}
+```
+
+Additional debug output
+-----------------------
+
 Because of Codeception buffers all output you can't make simple `var_dump()` in the TestCase, instead you need to use
 `Codeception\Util\Debug::debug()` function and then run test with `--debug` key, for example: