MNT Add behat test for form validation

tests/behat/features/validation.feature

@@ -0,0 +1,26 @@
+Feature: Form validation
+  As a content author
+  I want form validation to work in the CMS
+  So that I know my data is sane
+
+  Background:
+    Given the "Company" "Walmart" with "Category"="Retail"
+    And the "Company" "ExxonMobil" with "Category"="Oil"
+    And the "Company" "Vitol" with "Category"="Other"
+    And the "group" "EDITOR" has permissions "Access to 'Pages' section" and "Access to 'Test ModelAdmin' section" and "TEST_DATAOBJECT_EDIT"
+    And I am logged in as a member of "EDITOR" group
+    And I go to "/admin/test/SilverStripe-FrameworkTest-Model-Employee"
+    And I press the "Add Employee" button
+
+@gsat
+  Scenario: Field validation works as expected even if no validator is explicitly declared
+    When I fill in "Name" with "any name"
+    And I fill in "Email" with "invalid email"
+    And I press the "Create" button
+    Then I should not see "Saved Employee"
+    And I should see "Please enter an email address"
+
+    And I fill in "Email" with "email@example.com"
+    And I press the "Create" button
+    Then I should see "Saved Employee"
+    And I should not see "Please enter an email address"