add more details to tests

Author: sleepyStick

source/transactions-convenient-api/tests/README.md

@@ -44,8 +44,23 @@ private API or using a mock timer.
 ### Retry Backoff is Enforced
 
 Drivers should test that retries within `withTransaction` do not occur immediately. Optionally, set BACKOFF_INITIAL to a
-higher value to decrease flakiness of this test. Configure a fail point that forces 30 retries. Check that the total
-time for all retries exceeded 1.25 seconds.
+higher value to decrease flakiness of this test. Configure a fail point that forces 30 retries like so:
+
+```json
+{
+    "configureFailPoint": "failCommand",
+    "mode": {
+        "times": 30
+    },
+    "data": {
+        "failCommands": ["commitTransaction"],
+        "errorCode": 24,
+    },
+}
+```
+
+Additionally, let the callback for the transaction be a simple `insertOne` command. Check that the total time for all
+retries exceeded 1.25 seconds.
 
 ## Changelog