An overview of how Intest works, with links to all of its important functions.

§1. Prerequisites. This page is to help readers to get their bearings in the source code for Intest, which is a literate program or "web". Before diving in:

§2. Instructions and their blocks. Intest is a C program, so it begins at Main. This works out where Intest is installed, which project Intest is to test, and where the file specifying the universe of tests is, but otherwise soaks up the command line arguments into an array of "instructions". For example, if the user typed:

    $ intest/Tangled/intest inform7 -verbose 1 2 Gelato

then the instructions array will be -verbose, 1, 2, Gelato.

Main then calls out to Historian::research to look at the project's test history log, and uses that to make substitutions: this is where ?3 might be expanded into previous testing command number 3, or 6 might be expanded into the test case name for currently-failing test number 6. In the case of the example above, the instructions might now be -verbose, Sackcloth, Beatles, Gelato.

Once The Historian is done, the instructions are passed to Instructions::read, which parses them much more fully (see below) and returns an intest_instructions object.

Main then deals with a few incidental configuration switches — for example, turning on or off coloured terminal text output — and then calls Globals::create_platform. This creates the first global variable available to testing scripts: $$platform, which might be, say, "windows". A little later, $$workspace follows, the path to the temporary filing system space used by Intest. Globals always have these double-dollar-signed names, and are also created by USING blocks (see below): see the functions Globals::set and Globals::get. Globals have only one data type — they all hold text; but they are often just file system locations written out longhand. See Globals::to_pathname and Globals::to_filename.

All is now prepared, and Main simply hands over the intest_instructions to Actions::perform. Once that completes, Historian::write_up is called to update the history log, and Intest returns 1 if errors occurred or 0 if they didn't, in traditional Unix fashion. Note that a return code of 0 doesn't mean the tests all passed, only that they were all carried out; you get a return code of 1 if, for example, you ask for a nonexistent test, but if you ask to test Gelato and it fails, the return code is 0.

§3. Let's take a closer look at how Instructions::read turns an array like -verbose, Sackcloth, Beatles, Gelato into an intest_instructions object. It divides the array into contiguous runs called "blocks", each of which is either:

In the case of our example, there are just two blocks:

    -verbose   Sackcloth Beatles Gelato

USING blocks are passed to RecipeFiles::read_using_instructions. DO blocks are passed to Actions::read_do_instructions, but only after the OPTIONS block has been acted on, and after RecipeFiles::read has parsed the recipe file for the project being tested. This ordering is important, because it means the universe of available test cases is fully known before a DO block is parsed. For example, it will be known that Gelato is the name of an available test case.

§4. The Universe of Cases. -using is seldom needed and could probably be dropped from Intest, but USING blocks are essential and are needed on every run. This paradox is explained by the fact that non-recipe commands in recipe files are in fact USING blocks. Thus, if you type

    $ intest/Tangled/intest example all

you've given only a DO block (all), but if example/Tests/example.intest begins:

    -cases 'example/Tests/Test Cases'

then it's as if you had typed

    $ intest/Tangled/intest example -using -cases 'example/Tests/Test Cases' -do all

because lines like that in the recipe file are sent to RecipeFiles::read_using_instructions as USING blocks.

§5. So what can USING blocks contain? A minimal amount of conditionality allows for platform differences to be handled by -if X, ..., -endif: this works by checking X against the $$platform global. -set calls Globals::create to make new globals, and Globals::set to initialise them. But except for a few side-shows like these, the business is to discover the universe of test cases.

That universe is stored as a list of test_source objects, each of which holds a list of test_case objects coming from them. (There is one test_case for each individually testable case.) Sources might be single named files, files containing multiple test cases embedded in some elaborate way (as with Inform 7 extensions), or directories holding batches of tests.

The work is done by RecipeFiles::scan_directory_for_cases and RecipeFiles::scan_file_for_cases; the former calls the latter on its contents, but the latter is also called directly when the USING command names a single file rather than a directory.

RecipeFiles::scan_file_for_cases makes one or more cases out of a single file. In simple cases, the file is the test case, and all we need do is hand down to RecipeFiles::new_case. In more complicated cases, the file is in some elaborate format inside of which test cases are embedded, and we have to call The Extractor to extricate them: either way, though, the end result is that RecipeFiles::new_case makes each test_case object.

What we get for our trouble is a function, RecipeFiles::find_case, which returns the test_case for a test name like Gelato, or returns NULL if no test has that name.

§6. Instructions for action. As noted above, DO blocks are parsed by Actions::read_do_instructions. They typically tell Intest to perform an action on one or more test cases, perhaps named individually, perhaps collectively. There are around 20 actions, but the default is -test, so that our example DO block of Sackcloth Beatles Gelato is actually parsed as if it were -test Sackcloth Beatles Gelato.

The DO block is converted into a list of action_item objects, each made by Actions::create. For -test Sackcloth Beatles Gelato, there would be three, just as if we had typed -test Sackcloth -test Beatles -test Gelato. On the other hand, -test all produces only one action_item. This is because an action item is an instruction to act on all test cases which match a case_specifier, and while that can be an explicit name like Sackcloth, it can also be a "wildcard" like all or extensions, or even everything in a named group, or everything whose name matches a regular expression. See Actions::parse_specifier for the syntax.

§7. Performing actions. At this point in the story, then, the instructions have been fully read, and the recipe file has been read too. The universe of cases is known, and it's known what the user wants us to do with which subsets of those cases. Main has just called Actions::perform, and it's time for something to happen.

Actions::perform begins by calling Hasher::read_hashes to discover any MD5 hashes of known-to-be-correct test cases, and finishes by calling Hasher::write_hashes to update these. Otherwise, it works by acting on each action_item in turn. Some actions, such as -find or -catalogue, are taken care of immediately, but most, such as -test or -bless, are "scheduled" by calling Scheduler::schedule. This does not act immediately but, as the name suggests, schedules the tests for later: that later comes at the end of Actions::perform, when it calls Scheduler::test.

The reason for doing that is that The Scheduler must allocate tests to individual threads. The expectation is that if the host computer has \(N\) processor cores, then there will be \(N\) simultaneous testing threads running, and it's The Scheduler which spreads the tests out, rather as if it were dealing out a pack of cards to \(N\) players sitting around a table.

Each thread runs from Scheduler::perform_work, a function which runs through its tests — its hand of cards, as it were — and then marks itself idle so that Scheduler::perform_work, which is asleep on the main thread but wakes once per second to check on the workers, can then close it. Once all threads have finished, and Intest is back to being a single-threaded program, Scheduler::perform_work summarises the results.

§8. Individual tests. What the workers do is to call Tester::test on each test it is given. A test object is essentially an action code, plus a test_case, plus a work area in the file system — each worker thread has its own work area, since otherwise interference between them would create havoc; but successive tests run by the same worker use the same work area, which is cleaned after each use by Tester::purge_work_area.

The bulk of Tester::test, though, is an interpreter for the "recipe" program — that is, the Delia program assigned to the test case in question, which has been precompiled into a quick-to-interpret form by The Delia Compiler, something which was done back when the recipe file was read in.

§9. The most complex algorithm in Intest is probably the one performing token expansion, at Tester::expand. This expands a token like $WORK/Example.inform by substituting in the current value of the variable $WORK — note that these are single-dollar, i.e. local to the current recipe, variables, as distinct from the double-dollar, global, ones. That expansion process isn't so simple because if $WORK expands to a filename with spaces in, then we may need to end up with something which still ends up as a single shell command token — see Tester::quote_expand for how this is done.

§10. When tests fail, it is usually because some output text doesn't match the "blessed" text which had been expected — only usually, because Delia recipes can fail tests for quite a number of reasons. Still, this is the commonest case, and then The Differ performs a Unix-style diff (i.e., summary of differences) which can be reported back at the command line. The Differ is a somewhat crude mechanism, probably the weakest part of Intest at present: though it presents its output nicely, which is valuable, it has terrible running time on really enormous outputs; in those cases, the Unix diff tool would do rather better. More work could probably be done here.

§11. Intest used inside the Inform GUI app. On MacOS, the Inform application includes a copy of the intest binary, and uses it to perform automated testing of the test cases in an extension, for extension projects. This requires us to generate output in a different format, since we're reporting back to the app rather than to the user at the command line. See The Reporter for how this is done.

§12. Adding to Intest. Here's some miscellaneous advice for those who would like to add to Intest:

1. If what you want is to have a form of test which runs differently, see first if this can be accomplished with a Delia recipe combined, perhaps, with use of -set to create new global variables. The combination is quite potent.

2. But if that isn't good enough, try to do it with a minimal extension to the Delia language. You'll need to make matching changes to Delia::compile and Tester::test, and to add documentation to Writing Intest Recipes.

3. If that still isn't good enough, and what you really need is a different way to process existing recipes, see if a new action — such as -test, -bless, -rebless and so on — would meet your needs. If so, add this to Actions::read_do_instructions and Actions::perform, and document it at Intest at the Command Line.

4. Only if that really can't cope should you add a new OPTION block option, but if so, see Instructions::read and Instructions::respond, and again, document at Intest at the Command Line.

5. If what you want is to expand the universe of test cases in a new way — say, to pull them down from some Internet-based repository rather than read them from local files — create a new category of test_source, and add this to RecipeFiles::read_using_instructions.

6. As with any program built on Foundation, if you are creating a new class of object, don't forget to declare it in Basics.