MDL-38943 behat: New test

According to MDLQA-2417, teachers can
specify unique group and grouping ID numbers.

group/tests/behat/id_uniqueness.feature

@@ -0,0 +1,68 @@
+@core_group
+Feature: Uniqueness of Group ID number
+  In order to create unique groups and groupings
+  As a moodle teacher
+  I need to create groups with unique identificators
+
+  Background:
+    Given the following "courses" exists:
+      | fullname | shortname | category |
+      | Course 1 | C1 | 0 |
+    And the following "users" exists:
+      | username | firstname | lastname | email |
+      | teacher1 | Teacher | 1 | teacher1@asd.com |
+    And the following "course enrolments" exists:
+      | user | course | role |
+      | teacher1 | C1 | editingteacher |
+    And I log in as "teacher1"
+    And I follow "Course 1"
+    And I expand "Users" node
+    And I follow "Groups"
+
+  @javascript
+  Scenario: Group ID number uniqueness
+    Given I press "Create group"
+    And I fill the moodle form with:
+      | Group name | Group 1 |
+      | Group ID number | G1 |
+    And I press "Save changes"
+    When I press "Create group"
+    And I fill the moodle form with:
+      | Group name | Group 2 |
+      | Group ID number | G1 |
+    And I press "Save changes"
+    Then I should see "This ID number is already taken"
+    And I fill the moodle form with:
+      | Group ID number | G2 |
+    And I press "Save changes"
+    And I select "Group 1 (0)" from "groups"
+    And I press "Edit group settings"
+    And I fill the moodle form with:
+      | Group ID number | G2 |
+    And I press "Save changes"
+    And I should see "This ID number is already taken"
+    And I press "Cancel"
+
+  @javascript
+  Scenario: Grouping ID number uniqueness
+    Given I follow "Groupings"
+    And I press "Create grouping"
+    And I fill the moodle form with:
+      | Grouping name | Grouping 1 |
+      | Grouping ID number | GG1 |
+    And I press "Save changes"
+    When I press "Create grouping"
+    And I fill the moodle form with:
+      | Grouping name | Grouping 2 |
+      | Grouping ID number | GG1 |
+    And I press "Save changes"
+    Then I should see "This ID number is already taken"
+    And I fill the moodle form with:
+      | Grouping ID number | GG2 |
+    And I press "Save changes"
+    And I click on "Edit" "link" in the "Grouping 1" table row
+    And I fill the moodle form with:
+      | Grouping ID number | GG2 |
+    And I press "Save changes"
+    And I should see "This ID number is already taken"
+    And I press "Cancel"