update test data README

bagel/tests/data/README.md

@@ -1,6 +1,6 @@
 # Test data
 
-Example inputs to the CLI
+## Example inputs to the `bagel pheno` CLI command
 
 | Example name | `.tsv` | `.json` | Expect |
 | ----- | ----- | ----- | ----- |
@@ -31,5 +31,19 @@ Example inputs to the CLI
 
 `* this is expected to fail until we enable multiple participant_ID handling`.
 
+## Example inputs to the `bagel derivatives` command
+Designed to work with `.jsonld` files from the [Neurobagel reference example dataset](https://github.com/neurobagel/neurobagel_examples).
+
+proc_status | Description | Expected result
+----- | ----- | -----
+_synthetic.tsv | Captures a subset of subject-sessions represented in the BIDS examples synthetic dataset | Pass
+_synthetic.csv | Same as proc_status_synthetic.csv, but is a CSV file | Fail
+_unique_subs.tsv | Includes subjects not found in the phenotypic dataset | Fail
+_incomplete.tsv | Has a missing value in the `bids_participant` column | Fail
+_unique_sessions.csv | Includes a unique subject-session (`sub-01`, `ses-03`) not found in the synthetic dataset | Pass
+_missing_sessions.tsv | One subject (`sub-02`) is missing all session labels | Pass
+_no_bids_sessions.tsv | Has session labels in all rows for `session_id`, but no values in `bids_session` column | Pass
+
+
 ## Example expected CLI outputs
 You can find example expected CLI outputs [here](https://github.com/neurobagel/neurobagel_examples).