you have activated the services RMTSAMPLEFLIGHT and TEA_TEST_APPLICATION using transaction /IWFND/MAINT_SERVICE
These test cases can be created in the the test group CORE_SAMPLES from within the Gateway client.
The currently 75 test cases span from showing how to use $batch, $filter and other query parameters such as $skip, $top and so on.
Of special interest might be that several request are contained that show how to call services using $batch which requires the consumer to carefully build an http request that fits to the OData standard.
You can generate the test cases as follows:
Start the Gateway client using transaction /IWFND/GW_CLIENT
Choose Select as if you were to select an existing test case from the database, choose Select
From the menu choose Gateway Client (1) and then Create Core Samples (2)
This will create a list of currently 75 test cases:
By selecting one of the entries you open the Gateway Client like shown in the following with a $batch request.