Add test for changing dynamic collection datatype

lib/galaxy_test/api/test_workflows.py

@@ -4000,6 +4000,36 @@ def test_change_datatype_collection_map_over(self):
             assert forward["object"]["file_ext"] == "csv"
             assert reverse["object"]["file_ext"] == "csv"
 
+    @skip_without_tool("collection_split_on_column")
+    def test_change_datatype_discovered_outputs(self):
+        with self.dataset_populator.test_history() as history_id:
+            jobs_summary = self._run_workflow(
+                """
+class: GalaxyWorkflow
+inputs:
+  input: data
+steps:
+  split:
+    tool_id: collection_split_on_column
+    in:
+      input1: input
+    outputs:
+        split_output:
+          change_datatype: csv
+outputs:
+  output:
+    outputSource: split/split_output
+test_data:
+  input: "1\t2\t3"
+""",
+                history_id=history_id,
+            )
+            inv = self.workflow_populator.get_invocation(jobs_summary.invocation_id, step_details=True)
+            details = self.dataset_populator.get_history_collection_details(
+                history_id=history_id, content_id=inv["output_collections"]["output"]["id"]
+            )
+            assert details["elements"][0]["object"]["file_ext"] == "csv"
+
     @skip_without_tool("collection_type_source_map_over")
     def test_mapping_and_subcollection_mapping(self):
         with self.dataset_populator.test_history() as history_id: