AWS COMPREHEND method costs

I am trying to implement integration's test of a spring boot application that connects to aws amazon comprehend and start some machine learning operation. In my test, I instantiate my AmazonComprehend client with my aws credentials and then I want to test if it is correct so I call the method listEntitiesDetectionJobs.

ListEntitiesDetectionJobsRequest request = new ListEntitiesDetectionJobsRequest()
println amazonComprehend.listEntitiesDetectionJobs(request)

My question is: Is this method free of costs? Because I don't want to pay anytime I run this test.

Is there a standard way to test aws credentials in a spring boot application?