Performing API testing

Verifying an API is one of my favorite types of testing. The coding you need is generally straightforward and accessible, requiring a few complex tools and a little setup. Best of all, APIs usually have detailed and exhaustive documentation, either created directly from the source code or as part of customer-facing documents.

Using that documentation as your test basis, API testing involves stepping through each message and field and systematically trying different values. See the Testing variable types section for the important equivalence partitions for common data types. You can choose what level of coverage you need to reach, varying from a single check that fields are accepted to exhaustive testing of valid and invalid inputs.

APIs can vary greatly. Hideous binary, tag-length-value, or fixed-width protocols have to be completely specified in advance and need to be decoded before they become human-readable. If you are using a text-based SOAP or REST...