Automated testing of backend functionality such as SOAP and REST endpoints is normally quite cost effective. Backend interfaces tend to be fairly stable, so the corresponding tests will also require less maintenance effort than GUI tests, for instance.

The tests can also be fairly easy to write with tools such as soapUI, which can be used to write and execute tests. These tests can also be run from the command line and with Maven, which is great for Continuous Integration on a build server.

The soapUI is a good example of a tool that appeals to several different roles. Testers who build test cases get a fairly well-structured environment for writing tests and running them interactively. Tests can be built incrementally.

Developers can integrate test cases in their builds without necessarily using the GUI. There are Maven plugins and command-line runners.

The command line and Maven integration are useful for people maintaining the build server too.

Furthermore...