Controlled toggle rate of non-test signals during modular scan testing of an integrated circuit

A method is provided to test a modular integrated circuit (IC) 100 comprising: testing a module-under-test (MUT) 101B within the IC 100 while causing a controlled toggle rate within a first neighbor module 101A of the MUT 101B; wherein the controlled toggle rate within the first neighbor module 101A is selected so that toggling within the first neighbor module 101A has substantially the same effect upon operation of the MUT 101B as operation of the first neighbor module 101A would have during actual normal functional operation of the first neighbor module 101A.