Add test for abbreviations in Call To Action elements

This test is currently failing as abbreviations within Call To Action
elements do not currently work (as reported by a user).

This functionality will be added in later commits.

test/govspeak_test.rb

@@ -622,6 +622,21 @@ class GovspeakTest < Minitest::Test
     )
   end
 
+  test_given_govspeak "
+    $CTA
+    Contact the SGD on 0800 000 0000 or contact the OGD on 0800 001 0001
+    $CTA
+
+    *[OGD]: Other Government Department
+    *[SGD]: Some Government Department
+    " do
+    assert_html_output %(
+      <div class="call-to-action">
+      <p>Contact the <abbr title="Some Government Department">SGD</abbr> on 0800 000 0000 or contact the <abbr title="Other Government Department">OGD</abbr> on 0800 001 0001</p>
+      </div>
+    )
+  end
+
   test_given_govspeak "
     1. rod
     2. jane