DejaGnu is a framework for testing other programs. Its purpose is to provide a single front end for all tests. Think of it as a custom library of Tcl procedures crafted to support writing a test harness. A test harness is the testing infrastructure that is created to support a specific program or tool. Each program can have multiple testsuites, all supported by a single test harness. DejaGnu is written in Expect, which in turn uses Tcl — Tool command language.