diff --git a/gate_v1_function/tests/data/delta_cases.csv b/gate_v1_function/tests/data/delta_cases.csv
new file mode 100644
index 0000000..451fa43
--- /dev/null
+++ b/gate_v1_function/tests/data/delta_cases.csv
@@ -0,0 +1,11 @@
+stratum,from_status,to_status,unknown_reason
+StratumA,PASS,FAIL,
+StratumB,WARN,FAIL,
+StratumC,PASS,UNKNOWN,network_fluctuation
+StratumD,UNKNOWN,PASS,temporary_sensor_error
+StratumE,PASS,REVIEW,
+StratumF,WARN,UNKNOWN,deprecated_model_version
+StratumG,PASS,FAIL,
+StratumH,FAIL,PASS,
+StratumI,UNKNOWN,UNKNOWN,external_dependency_issue
+StratumJ,PASS,UNKNOWN,missing_label_mapping