In an arrangement for testing multiple low-end computing devices simultaneously, different tests are executed simultaneously on different platforms using a single instance of a test harness to which multiple devices are connected. A platform-specific API is provided for independent components of the tests and platform-specific components are implemented for each test according to the respective platform-specific API. At run-time the test harness deploys each test together with a platform-specific execution agent, configured according to the components of the test. The agents execute the test suites, and return test results to the test harness.