(Also see Additional Setup for Hooking up Qt Sub-Processes on Windows Non-Invasively (Section 7.7.2.2) for an alternative approach to this.)

To enable Squish for Qt to hook up sub-processes of the AUT on Windows a small change to the AUT's source code is required, which essentially results in starting the sub-process through a wrapper program (SQUISH_DIR/bin/dllpreload.exe).

The required change to the AUT can be made so that it is only enabled when the AUT gets started via Squish, for example by checking for the existence of an environment variable called SQUISH_PREFIX. (Squish sets this environment variable for the AUT process.)

For example, suppose that the AUT had the following source code to start a sub-process:

QProcess process;
process.start("subprogram.exe");

To change this to work with Squish, change the AUT in two ways. First add a new command line argument, say --testing, that when given sets a global Boolean, say, TESTING to true. Now update the code that calls the subprocess as follows:

QProcess process;
QStringList commands;
#ifdef Q_OS_WIN32
if (TESTING)
    commands.append("dllpreload.exe");
#endif
commands.append("subprogram.exe");
process.start(commands[0], commands.mid(1));

When TESTING isn't defined the commands string list will only contain one item ("subprogram.exe"), and commands.mid(1) will harmlessly return an empty list.

To make the change effective, in the Test Suite Settings view (Section 8.2.16) (or for Squish 3, the Test Suite Settings dialog), add --testing to the AUT's Arguments.

Now, when Squish executes the AUT on Windows and the sub-process is started, what will actually happen is that Squish's dllpreload.exe program will be started with the intended application (e.g., subprogram.exe) as its first argument, and any other arguments passed as arguments to the intended application as normal. This means that the AUT and sub-process' behavior will be exactly what it was before.

When recording sub-processes, the test script will contain calls to the waitForApplicationLaunch function. This function returns an ApplicationContext object for each application started as a sub-process. (See also, Application Context (Section 6.3.12).) Using context objects makes it possible to tell Squish which application it should be interacting with at various points in the test script's execution. (See How to Use ApplicationContext Objects (Section 5.12.3) for details about working with application contexts.)

(Also see Additional Setup for Hooking up Qt Sub-Processes on Windows (Section 7.7.2.1) for an alternative approach to this.)

To enable Squish for Qt to hook up sub-processes of the AUT on Windows without a change to the AUT's source code (as described in the alternative approach at Additional Setup for Hooking up Qt Sub-Processes on Windows (Section 7.7.2.1)) the following steps must be performed:

Now, when the AUT is executed, it is really dllpreload.exe that gets executed, and dllpreload.exe is smart enough to check the name it was called as and will try to execute the executable with the same name but with an underscore before the period.