diff --git a/test/functional/tools/collection_creates_dynamic_list_of_pairs.xml b/test/functional/tools/collection_creates_dynamic_list_of_pairs.xml
index cfd79948c66..bd56401b0a3 100644
--- a/test/functional/tools/collection_creates_dynamic_list_of_pairs.xml
+++ b/test/functional/tools/collection_creates_dynamic_list_of_pairs.xml
@@ -17,6 +17,11 @@
   </inputs>
   <outputs>
     <collection name="list_output" type="list:paired" label="Duplicate List">
+      <!-- Use named regex group to grab pattern
+           <identifier_0>_<identifier_1>.fq. Here identifier_0 is the list
+           identifier in the nested collection and identifier_1 is either
+           forward or reverse (for instance samp1_forward.fq).
+      -->
       <discover_datasets pattern="(?P&lt;identifier_0&gt;[^_]+)_(?P&lt;identifier_1&gt;[^_]+)\.fq" ext="fastqsanger" visible="true" />
     </collection>
   </outputs>
diff --git a/test/functional/tools/collection_creates_dynamic_nested.xml b/test/functional/tools/collection_creates_dynamic_nested.xml
index 99f08b6773a..68edc0cc34b 100644
--- a/test/functional/tools/collection_creates_dynamic_nested.xml
+++ b/test/functional/tools/collection_creates_dynamic_nested.xml
@@ -12,6 +12,11 @@
   </inputs>
   <outputs>
     <collection name="list_output" type="list:list" label="Duplicate List">
+      <!-- Use named regex group to grab pattern
+           <identifier_0>_<identifier_1>.fq. Here identifier_0 is the list
+           identifier of the outer list and identifier_1 is the list identifier
+           of the inner list (for instance oe1_ie2.fq in above example).
+      -->
       <discover_datasets pattern="(?P&lt;identifier_0&gt;[^_]+)_(?P&lt;identifier_1&gt;[^_]+)\.fq" ext="fastqsanger" visible="true" />
     </collection>
   </outputs>