Methods and apparatus for enabling efficient testing of application programming interface (API) frameworks and application code are disclosed. According to one aspect of the present invention, a framework suitable for use to test an API includes a metadata provider arrangement that stores declarative metadata and a metadata provider interface that obtains the declarative metadata associated with a test from the declarative metadata provider. A first test adapter includes logic used to process the declarative metadata, and a diagnostic test interface cooperates with the first test adapter to execute the test. The first test adapter is effectively interfaced with the diagnostic test interface. Finally, a diagnostics execution engine is arranged to communicate with the diagnostic test interface to cause the test to be executed.