1. A system for testing computer software, comprising: a plurality of heterogeneous test tools; a testing application that provides a single user interface that enables a user to collectively access each of said plurality of heterogeneous test tools; and a plurality of modules that interact with said testing application to enable the user to create and modify, via said interface, a test that is implemented with said plurality of test tools, including: a tool manager module that enables the user to select one or more tools, from among said plurality of test tools, to be employed in a test; a case manager module that enables the user to select test cases, each comprising an elemental executable test, that are performed by selected tools, for inclusion in the test; and a suite manager module that enables the user to create, modify and select test suites, each comprising at least one group of selected test cases, to be executed during the test.