Functional safety and cybersecurity standards frequently require tests to be completed on target hardware, as for the worked example. However, the nature of TDD means that testing is required to begin very early in the project; perhaps before target hardware has been acquired or even fully specified.

It is also a consideration that target testing can be laborious, slow, and time-consuming if the target itself is of relatively low performance.

Such considerations need not restrict the use of TDD in a timely and efficient manner. Tests can be constructed and appropriate code developed using a simulator or, depending on the nature of each function, even the native compiler. Tests will need to be re-run later to comply with the standards.

However, the same mechanisms that make it easy to regress tests can be leveraged to re-run them on the target hardware. Such an approach opens up the possibility of developing some of the code without access to the hardware, or only leveraging that hardware for a confirmation test when each function is completed.

Using simulators: a pragmatic approach