Hi krogold,
Thank you for your post. I can suggest that you use the approach from this thread: use the File Wait test step to read your JSON file. The File Wait test step can wait for a file to appear, but more importantly, it reads its content to fileContent property, which you later can address to in JSON DataSource. File Wait test step has custom property fileContent. After the step is executed, this property will have the content of your file. You can access it in the following test steps using property expansion string - "${File Wait#fileContent}", where "File Wait" is the name of your File Wait step.
In case of JSON DataSource you should choose your File Wait step in Source Step and fileContent in Source property (see http://readyapi.smartbear.com/structure/sources/json/start). You should run the test case at least once to be able to select nodes from the actual file, using buttons next to Row Path and Column Paths fields.
So, you will need to do the following:
1. Write the received JSON to the file.
2. In the next testcase use the FileWait test step.
3. Read JSON from the File Wait test step.
The structure of the project will be the following:
TC1
REST request
DataSink (File type)
TC2
File Wait
DataSource (JSON type)
