Documentation Update: Using directories to define groups (Codeception…

…#3921)

* Using directories to define groups

Closes Codeception#3919

* Update 07-AdvancedUsage.md

docs/07-AdvancedUsage.md

@@ -231,6 +231,7 @@ These examples can be written using Doctrine-style annotation syntax as well:
 ```
 
 You can also use the `@dataprovider` annotation for creating dynamic examples, using a protected method for providing example data:
+
 ```php
 <?php
    /**
@@ -260,6 +261,7 @@ You can also use the `@dataprovider` annotation for creating dynamic examples, u
 Alternatively, the `@dataprovider` can also be a public method starting with `_` prefix so it will not be considered as a test:
 
 ```php
+<?php
    /**
     * @dataprovider _pageProvider
     */
@@ -623,25 +625,31 @@ Feature: Admin area
 ### Group Files
 
 Groups can be defined in global or suite configuration files.
-Tests for groups can be specified as an array or as a path to a file containing a list of groups:
+Tests for groups can be specified as an array of file names or directories containing them:
 
 ```yaml
 groups:
   # add 2 tests to db group
   db: [tests/unit/PersistTest.php, tests/unit/DataTest.php]
-
-  # add list of tests to slow group
-  slow: tests/_data/slow
+  
+  # add all tests from a directory to api group
+  api: [tests/functional/api]
 ```
 
-For instance, you can create a file with the list of the slowest tests, and run them inside their own group.
-Group file is a plain text file with test names on separate lines:
+A list of tests for the group can be passed from a Group file. It should be defined in plain text with test names on separate lines:
 
 ```bash
 tests/unit/DbTest.php
 tests/unit/UserTest.php:create
 tests/unit/UserTest.php:update
 ```
+A group file can be included by its relative filename:
+
+```yaml
+groups:
+  # requiring a group file
+  slow: tests/_data/slow.txt
+```
 
 You can create group files manually or generate them from third party applications.
 For example, you can write a script that updates the slow group by taking the slowest tests from xml report.
@@ -655,6 +663,7 @@ groups:
 
 This will load all found `p*` files in `tests/_data` as groups. Group names will be as follows p1,p2,...,pN.
 
+
 ## Conclusion
 
 Codeception is a framework which may look simple at first glance