MASH is a modular, automated script harness. It allows users to implement simple harnesses that perform work external to a system. The framework will invoke that harness as outlined by an XML script. For example, when using the framework to test a system you could create a script that cleans and loads a database, FTPs some data, submits a login form, and verifies HTTP information. Harnesses can easily be built to do almost anything (many harnesses are provided), not just Web page verification. While harnesses are written in Java, the scripts may be run against any type of system as harnesses are intended to act as clients.
Mistletoe is a JUnit extension intended for integration testing. In technical terms, it is a JUnit test suite runner presenting the test results via HTTP as a Web page. Mistletoe, when incorporated within an application, will help diagnose integration issues. For example, an application that runs perfectly in the developer's environment may not run properly in the production environment due to configuration errors and connectivity issues. Instead of perusing log files, or looking at stack traces, mistletoe will run a user-specified series of tests and present the results in the form of a Web page served by the application itself. Since the tests are run within the context of the deployed application, given an appropriate test suite, you can home in on integration problems quickly and conveniently.