--- a
+++ b/tests/functional/test_serialize_definition.py
@@ -0,0 +1,29 @@
+import json
+from pathlib import Path
+
+import pytest
+
+
+FIXTURES_PATH = Path(__file__).parents[1] / "fixtures" / "good_definition_files"
+
+
+@pytest.mark.parametrize(
+    "definition_type,definition_file",
+    [
+        ("dataset", FIXTURES_PATH / "dataset_definition.py"),
+        ("measures", FIXTURES_PATH / "measure_definitions.py"),
+        ("test", FIXTURES_PATH / "assurance.py"),
+    ],
+)
+def test_serialize_definition(definition_type, definition_file, call_cli):
+    captured = call_cli(
+        "serialize-definition",
+        "--definition-type",
+        definition_type,
+        definition_file,
+    )
+    # We rely on tests elsewhere to ensure that the serialization is working correctly;
+    # here we just want to check that we return valid JSON
+    assert json.loads(captured.out)
+    # We shouldn't be producing any warnings or any other output
+    assert captured.err == ""