whenPOST(url, [data], [headers], [keys]);
Creates a new backend definition for POST requests. For more info see when(). 
Parameters
Param Type Details  url   stringRegExpfunction(string)   HTTP url or function that receives a url and returns true if the url matches the current definition.   data (optional)   stringRegExp   HTTP request body.   headers (optional)   Objectfunction(Object)   HTTP headers.   keys (optional)   Array   Array of keys to assign to regex matches in request url describe