Controllability refers to the degree to which a system, such as the System Under Test (SUT), allows inputs to be injected in a controlled manner. When the SUT provides interfaces that can be used to perform actions on it, this characteristic is essential for test automation because it enables the test engineer to manipulate the system’s state and behavior during testing. Controllability is crucial for ensuring that tests can be performed consistently and effectively, as it allows for precise control over the test conditions. References = ISTQB materials define controllability as a key attribute of a testable system. It is discussed in the context of test automation, particularly in relation to the interfaces provided by the SUT that allow for controlled manipulation during testing12.