  Test coverage is a standard measure used to evaluate the completeness of a
test suite. Coverage is typically computed on source code, by assessing the
extent of source code entities (e.g., statements, data dependencies, control
dependencies) that are exercised when running test cases. When considering REST
APIs, an alternative perspective to assess test suite completeness is with
respect to the service definition. This paper presents Restats, a test coverage
tool for REST APIs that supports eight state-of-the-art test coverage metrics
with a black-box perspective, i.e., only relying on the OpenAPI interface
specification of the REST API under test. In fact, metrics are computed by only
observing the HTTP requests and responses occurring at testing time, and no
access to source/compiled code of the REST API is required. These coverage
metrics come in handy for: (i) developers and test engineers working at
development and maintenance tasks; (ii) stakeholders and customers who want to
evaluate the completeness of acceptance tests; (iii) researches interested in
comparing different automated test case generation strategies.
