Testware is documentation of tests to be executed on a particular software. It also includes supporting documents such as one that defines the test setup, test data generation.
Testware design in a V Testing model (the software model in which development and testing of software takes place parallelly) is done before the software is delivered to QA for testing.
Testware design includes documentation of test setup, test beds, tests to be executing covering each and every aspect of software (functional, performance, load etc.).
At the later phase- the documentation of test results also forms a part of testware.