The run-tests.sh script is called by various testers to do the work of testing. Each test is actually fairly simple: it is a comparison of standard output and standard error, as per the program specification.

In any given program specification directory, there exists a specific tests/ directory which holds the expected return code, standard output, and standard error in files called n.rc, n.out, and n.err (respectively) for each test n. The testing framework just starts at 1 and keeps incrementing tests until it can't find any more or encounters a failure. Thus, adding new tests is easy; just add the relevant files to the tests directory at the lowest available number.

The files needed to describe a test number n are:

• n.rc: The return code the program should return (usually 0 or 1)
• n.out: The standard output expected from the test
• n.err: The standard error expected from the test
• n.run: How to run the test (which arguments it needs, etc.)
• n.desc: A short text description of the test
• n.pre (optional): Code to run before the test, to set something up
• n.post (optional): Code to run after the test, to clean something up

There is also a single file called pre which gets run once at the beginning of testing; this is often used to do a more complex build of a code base, for example. To prevent repeated time-wasting pre-test activity, suppress this with the -s flag (as described below).

In most cases, a wrapper script is used to call run-tests.sh to do the necessary work.

The options for run-tests.sh include:

• -h (the help message)
• -v (verbose: print what each test is doing)
• -t n (run only test n)
• -c (continue even after a test fails)
• -d (run tests not from tests/ directory but from this directory instead)
• -s (suppress running the one-time set of commands in pre file)

There is also another script used in testing of xv6 projects, called run-xv6-command.exp. This is an expect script which launches the qemu emulator and runs the relevant testing command in the xv6 environment before automatically terminating the test. It is used by the run-tests.sh script as described above and thus not generally called by users directly.