To set the scene, the Ada software under test (SUT) forms part of a system. Generally, the system will be constructed using a layered approach, and the other parts of the system that interact with the SUT are higher-level (which can call interface subprograms presented by the SUT) or lower-level (whose interfaces can be called by the SUT, or which can provide callbacks to the SUT).

This package is intended for testing at a level between unit testing (using, for example, AUnit) and integration testing (using real hardware). Unit testing tends to be fragile, requiring a lot of rework for even minor functional changes in the requirements.

The scripting language supported is Tcl, and specifically the Ada binding Tash. The reason for choosing Tcl rather than Python or Lua is that Tcl’s interface is entirely string-based; this is important, considering the need to specify values of enumerated types.

The package provides facilities to write new commands in Tcl to

• call the interface subprograms presented by the SUT,

• set up values to be returned by calls the SUT makes to lower-level system components,

• call callbacks provided by lower-level system components,

• delay for appropriate periods, and

• check that the proper calls have been made to lower-level system components, with the required values.

It’s assumed that the interface subprograms of the lower-level subsystems are stubbed so that:

• in and in out parameters can be recorded for later checking,

• out (and in out) parameter values and function return values can be provided to be returned to the SUT,

• exceptions can be raised when required,

• the number of calls to the subprogram can be checked.