ModTest enables you to define Modbus commands together with their expected results, and send them to a Modbus slave. ModTest will automatically compare the actual results from the slave with the expected results, and flag any differences as test failures. The commands can be saved and then used as "test suite" for regression testing or for testing other slaves.

The commands that you define may be standard Modbus commands, custom commands, or arbitrary data. This makes it easy to test the error handling of the Modbus slave.