Existing methods of automated testing of web service APIs require additional tools to extract API related details and configuration files to create test cases. The method and system disclosed herein taps annotations present in code of web service APIs to extract API related details and creates test cases using the extracted data. The method disclosed herein describes an approach to identify resource classes related to a plurality of web service APIs using built-in annotations in code of web application under test. Further, the identified resource classes are scanned to extract API related details (metadata) using built-in annotations and annotations given by a developer. Further, the extracted metadata is forwarded to a test engine server which generates a plurality of test cases using the extracted metadata. Further, the plurality of web service APIs are tested using the generated test cases.