What Intest is, and a simple example of what it can do.

§1. Introduction. Intest is a command line tool for testing command line tools. It was originally written for testing the Inform 7 compiler, and has been used heavily and continuously for that purpose since 2004. But it can in fact test any command-line tool with broadly textual output. While it's a natural sidekick for the literate programming tool Inweb, it can work just as easily on programs written by other means.

Intest is at its best when running a batch of tests, each of which can follow a complex multi-stage sequence if necessary. Tests are automatically spread across multiple threads so that the batch can be finished as soon as possible, and results are tidily collated. Intest has a command-line syntax which makes a sort of conversation possible: start by testing a batch, then retest those which fail, fixing them one by one, and so on. For example,

    $ intest/Tangled/intest -from myproject all
    myproject -> cases: [1] [2] [3] [4]
    Discrepancy at line 7:
        Planet is: Joopiter
    [5] planets produced incorrect output
    [6] [7] [8] [9]
      8 tests succeeded but 1 failed (time taken 0:02, 9 simultaneous threads)
    Failed: 1=planets

Suppose we go fix that bug, and then retest:

    $ intest/Tangled/intest -from myproject 1
    Expanded to: ?322. planets
    [1] planets passed

Note that 1 was understood by Intest here as referring to the test case planets which failed earlier. Intest is recording a history of recent tests run, too: this one was test run ?322. We could have listed those by

    $ intest/Tangled/intest -from myproject ?

and recalled any of them by number:

    $ intest/Tangled/intest -from myproject ?315
    Repeating: ?315. rockets moons
    [1] rockets passed
    [2] moons passed

§2. Recipes. Intest assumes that each project will have its own universe of tests. These can take many forms, but the commonest are to give valid input and check to see some expected output, or else to give invalid input and check to see that some expected error message is produced.

Each individual test is performed by following a "recipe". Recipes are simple mini-language called Delia, which sits on top of the host operating system's command-line shell. For example, here is Delia code for testing what ought to be a valid input to a tool called zap inside the myproject folder:

    set: $A = $PATH/_actual/$CASE.txt
    set: $I = $PATH/_ideal/$CASE.txt
    step: myproject/zap $PATH/$CASE.txt >$A 2>&1
    or: 'failed zap' $A
    show: $A
    match text: $A $I
    or: 'produced the wrong output'
    pass: 'passed'

This looks more forbidding than it is. Variables start with a dollar, as in most Unix mini-languages: they usually hold filenames. $CASE is the name of the current test case: perhaps "planets". $PATH is the pathname to its folder, which might be, for example, "myproject/tests". What happens is:

    set: $A = $PATH/_actual/$CASE.txt
    set: $I = $PATH/_ideal/$CASE.txt

This sets two filenames — it doesn't create these files, simply creates two names. $A is going to be the actual output printed out by the program being tested, while $I is the ideal output, that is, what it should have printed. Next:

    step: myproject/zap $PATH/$CASE.txt >$A 2>&1

A "step" is a stage in a test which involves issuing a shell command, and which passes or fails according to the exit code from that command, exactly as it would in a tool like make. We're going to assume zap is a simple sort of program, which takes one command-line argument — a filename — does something with that file, and prints out something interesting about it.

Intest substitutes in values for the variables, so the actual shell command might be:

    $ myproject/zap myproject/tests/planets.txt >myproject/tests/_actual/planets.txt 2>&1

which uses bash shell notation to redirect both printed output, and error messages, to the $A file. That, as promised, is the "actual output".

The next line in the recipe is then:

    or: 'failed zap' $A

This tells Intest to halt the test if the shell command failed (i.e., if zap exited with a non-zero exit value). Intest uses the brief epitaph "failed zap" when summarising what happened, and prints out $A, because presumably it ends with some error messages which the tester will want to see.

So the recipe is only continued if, in fact, zap did not produce error messages. The next line is not quite what it seems:

    show: $A

This tells Intest that if the tester ran the test specifying -show on the command line then $A is the right file to print out. If the tester didn't say -show, we print nothing here, and continue. The next steps in the recipe are more consequential:

    match text: $A $I
    or: 'produced the wrong output'

This does what it looks as if it should, but it has hidden powers. If the tester hasn't yet created a file of ideal output, then there's nothing to compare against. In that case Intest doesn't fail the stage, but it does mark it in the summary:

    $ intest/Tangled/intest -from myproject planets
    -1- planets passed

The notation -1-, rather than the more usual [1], conveys that the test was incompletely passed in this way. This is easy to fix. If we're happy with the actual output, we "bless" it:

    $ intest/Tangled/intest -from myproject -bless planets
    [1] planets passed

With -bless specified, when the recipe hits:

    match text: $A $I

Intest sets the ideal output to the actual output: the two then necessarily match, so the stage passes. (It's also possible to -curse a test, which deletes its ideal output, or to -rebless it, which replaces the current ideal output in favour of the current actual output — in effect, it performs a curse immediately followed by a blessing.)

Either way, if the recipe is still running at this point, all is good: zap produced no error messages, and we have output which is not known to be incorrect. So we conclude with a triumphant:

    pass: 'passed'

Recipes can be substantially longer and more elaborate, running through a sequence of tools, or running the same test material in a sequence of different ways. The recipes used by the main Inform compiler occupy about 400 lines like the above, though always with the same basic manoeuvres over and over again. A typical test batch for that project involves over 2000 cases. Intest is a simple tool at heart, but it was written with an eye to speed and flexibility.

§3. Installation. Intest is a "literate program", and to compile it from source you should first obtain the literate programming tool Inweb. (Both are available from Github.)

To begin, place the distribution directories intest and inweb in the same parent directory, and then change working directory to that. Thus, you should reach:

    $ ls
    intest   inweb

(and perhaps lots of other stuff too). Be sure to make Inweb first: see its own documentation for that. Then:

    $ inweb/Tangled/inweb intest -makefile intest/intest.mk

This makes the makefile we will use. It will automatically be configured suitably for the operating system we're using: the MacOS version of Inweb will make us a MacOS version of this makefile, and so on. Now we can make:

    $ make -f intest/intest.mk

All being well, you now have a working Intest. The executable is in intest/Tangled/intest, so:

    $ intest/Tangled/intest -help

should verify that it's in working order. A more interesting test is:

    $ intest/Tangled/intest -from inweb all

which runs the Inweb test suite (a very modest one, as it happens).

Users of, for example, the bash shell may want to

    $ alias intest='intest/Tangled/intest'

to save a little typing, but in this documentation we always spell it out.

§4. When it runs, Intest needs to know where it is installed in the file system. There is no completely foolproof, cross-platform way to know this (on some Unixes, a program cannot determine its own location), so Intest decides by the following set of rules:

If you're not sure what Intest has decided and suspect it may be wrong, running Intest with the -verbose switch will cause it to print its belief about its location as it starts up.

§5. Intest returns an exit code of 0 if successful, or else it throws errors to stderr and returns 1 if unsuccessful. Successful means that it did what it was asked to do: if it was asked to conduct a test and the test failed, Intest was still successful (the test was after all conducted), so it returns 0.