3 Michael Stapelberg <michael+i3@stapelberg.de>
6 This document explains how the i3 testsuite works, how to use it and how to
7 extend it. It is targeted at developers who not necessarily have been doing
8 testing before or have not been testing in Perl before. In general, the
9 testsuite is not of interest for end users.
14 The i3 testsuite is a collection of files which contain testcases for various
15 i3 features. Some of them test if a certain workflow works correctly (moving
16 windows, focus behaviour, …). Others are regression tests and contain code
17 which previously made i3 crash or lead to unexpected behaviour. They then check
18 if i3 still runs (meaning it did not crash) and if it handled everything
21 The goal of having these tests is to automatically find problems and to
22 automatically get a feel for whether a change in the source code breaks any
23 existing feature. After every modification of the i3 sourcecode, the developer
24 should run the full testsuite. If one of the tests does not pass (but fails),
25 the corresponding problem should be fixed (or, in some cases, the testcase has
26 to be modified). For every bugreport, a testcase should be written to test the
27 correct behaviour. Initially, it will fail, but after fixing the bug, it will
28 pass. This ensures (or increases the chance) that bugs which have been fixed
29 once will never be found again.
31 Also, when implementing a new feature, a testcase might be a good way to be
32 able to easily test if the feature is working correctly. Many developers will
33 test manually if everything works. Having a testcase not only helps you with
34 that, but it will also be useful for every future change.
38 For several reasons, the i3 testsuite has been implemented in Perl:
40 1. Perl has a long tradition of testing. Every popular/bigger Perl module which
41 you can find on CPAN will not only come with documentation, but also with
42 tests. Therefore, the available infrastructure for tests is comprehensive.
43 See for example the excellent http://search.cpan.org/perldoc?Test::More
44 and the referenced http://search.cpan.org/perldoc?Test::Tutorial.
46 2. Perl is widely available and has a well-working package infrastructure.
47 3. The author is familiar with Perl :).
49 Please do not start programming language flamewars at this point.
53 ==== Script: complete-run
55 The testcases are run by a script called +complete-run.pl+. It runs all
56 testcases by default, but you can be more specific and let it only run one or
57 more testcases. Also, it takes care of starting up a separate instance of i3
58 with an appropriate configuration file and creates a folder for each run
59 containing the appropriate i3 logfile for each testcase. The latest folder can
60 always be found under the symlink +latest/+. It is recommended that you run the
61 tests on one or more separate X server instances (you can only start one window
62 manager per X session), for example using the provided Xdummy script.
63 +complete-run.pl+ takes one or more X11 display specifications and parallelizes
64 the testcases appropriately:
66 .Example invocation of complete-run.pl+
67 ---------------------------------------
70 # start two dummy X11 instances in the background
74 $ ./complete-run.pl -d :1,:2
75 # output omitted because it is very long
77 Files=78, Tests=734, 27 wallclock secs ( 0.38 usr 0.48 sys + 17.65 cusr 3.21 csys = 21.72 CPU)
80 $ ./complete-run.pl -d :1 t/04-floating.t
81 [:3] i3 startup: took 0.07s, status = 1
82 [:3] Running t/04-floating.t with logfile testsuite-2011-09-24-16-06-04-4.0.2-226-g1eb011a/i3-log-for-04-floating.t
83 [:3] t/04-floating.t finished
85 output for t/04-floating.t:
86 ok 1 - use X11::XCB::Window;
87 ok 2 - The object isa X11::XCB::Window
88 ok 3 - Window is mapped
89 ok 4 - i3 raised the width to 75
90 ok 5 - i3 raised the height to 50
91 ok 6 - i3 did not map it to (0x0)
92 ok 7 - The object isa X11::XCB::Window
93 ok 8 - i3 let the width at 80
94 ok 9 - i3 let the height at 90
95 ok 10 - i3 mapped it to x=1
96 ok 11 - i3 mapped it to y=18
97 ok 12 - The object isa X11::XCB::Window
98 ok 13 - i3 let the width at 80
99 ok 14 - i3 let the height at 90
102 All tests successful.
103 Files=1, Tests=14, 0 wallclock secs ( 0.01 usr 0.00 sys + 0.19 cusr 0.03 csys = 0.23 CPU)
106 $ less latest/i3-log-for-04-floating.t
107 ----------------------------------------
111 The testsuite makes extensive use of the IPC (Inter-Process Communication)
112 interface which i3 provides. It is used for the startup process of i3, for
113 terminating it cleanly and (most importantly) for modifying and getting the
114 current state (layout tree).
116 See [http://i3wm.org/docs/ipc.html] for documentation on the IPC interface.
120 In order to open new windows, change attributes, get events, etc., the
121 testsuite uses X11::XCB, a new (and quite specific to i3 at the moment) Perl
122 module which uses the XCB protocol description to generate Perl bindings to
123 X11. They work in a very similar way to libxcb (which i3 uses) and provide
124 relatively high-level interfaces (objects such as +X11::XCB::Window+) aswell as
125 access to the low-level interface, which is very useful when testing a window
128 === Filesystem structure
130 In the git root of i3, the testcases live in the folder +testcases+. This
131 folder contains the +complete-run.pl+ and +Xdummy+ scripts and a base
132 configuration file which will be used for the tests. The different testcases
133 themselve can be found in the conventionally named subfolder +t+:
135 .Filesystem structure
136 --------------------------------------------
138 │ ├── complete-run.pl
143 │ │ ├── 02-fullscreen.t
145 │ │ ├── omitted for brevity
147 │ │ ├── 74-regress-focus-toggle.t
151 --------------------------------------------
153 == Anatomy of a testcase
155 Learning by example is definitely a good strategy when you are wondering how to
156 write a testcase. Let's take +t/11-goto.t+ as an easy example and go through it
159 .t/11-goto.t: Boilerplate
160 ----------------------
162 # vim:ts=4:sw=4:expandtab
167 my $x = X11::XCB::Connection->new;
168 -----------------------
170 This is what we call boilerplate. It exists at the top of every test file (to
171 some extent). The first line is the shebang, which specifies that this file is
172 a Perl script. The second line contains VIM specific settings on how to
173 edit/format this file (use spaces instead of tabs, indent using 4 spaces).
174 Afterwards, the +i3test+ module is used. This module contains i3 testsuite
175 specific functions which you are strongly encouraged to use. They make writing
176 testcases a lot easier and will make it easier for other people to read your
179 The next line uses the +File::Temp+ module. This is specific to this testcase,
180 because it needs to generate a temporary name during the test. Many testcases
181 use only the +i3test+ module.
183 The last line opens a connection to X11. You might or might not need this in
184 your testcase, depending on whether you are going to open windows (etc.) or
185 only use i3 commands.
188 ----------------------
189 my $tmp = fresh_workspace;
192 ----------------------
194 The first line calls i3test's +fresh_workspace+ function which looks for a
195 currently unused workspace, switches to it, and returns its name. The variable
196 +$tmp+ will end up having a value such as +"/tmp/87kBVcHbA9"+. Note that this
197 is not (necessarily) a valid path, it's just a random workspace name.
199 So, now that we are on a new workspace, we ensure that the workspace uses
200 horizontal orientation by issuing the +split h+ command (see the i3 User's
201 Guide for a list of commands). This is not strictly necessary, but good style.
202 In general, the +cmd+ function executes the specified i3 command by using the
203 IPC interface and returns once i3 acknowledged the command.
206 ----------------------
207 #####################################################################
208 # Create two windows and make sure focus switching works
209 #####################################################################
211 my $top = open_window($x);
212 my $mid = open_window($x);
213 my $bottom = open_window($x);
214 ----------------------
216 In every major section of a testcase, you should put a comment like the one
217 above. This makes it immediately clear how the file is structured.
219 The +open_window+ function opens a standard window, which will then be put into
220 tiling mode by i3. If you want a floating window, use the
221 +open_floating_window+ function. These functions accept the same parameters as
222 +X11::XCB::Window->new+, see the i3test documentation at TODO.
224 .t/11-goto.t: Helper function
225 ----------------------
227 # Returns the input focus after sending the given command to i3 via IPC
228 # end sleeping for half a second to make sure i3 reacted
235 return $x->input_focus;
237 ----------------------
239 This section defines a helper function which will be used over and over in this
240 testcase. If you have code which gets executed more than once or twice
241 (depending on the length of your test, use your best judgement), please put it
242 in a function. Tests should be short, concise and clear.
244 The +focus_after+ function executes a command and returns the X11 focus after
245 the command was executed. The +sync_with_i3+ command makes sure that i3 could
246 push its state to X11. See <<i3_sync>> to learn how this works exactly.
248 .t/11-goto.t: Test assumptions
249 ----------------------
250 $focus = $x->input_focus;
251 is($focus, $bottom->id, "Latest window focused");
253 $focus = focus_after('focus left');
254 is($focus, $mid->id, "Middle window focused");
255 ----------------------
257 Now, we run the first two real tests. They use +Test::More+'s +is+ function,
258 which compares two values and prints the differences if they are not the same.
259 After the arguments, we supply a short comment to indicate what we are testing
260 here. This makes it vastly more easy for the developer to spot which testcase
261 is the problem in case one fails.
263 The first test checks that the most recently opened window is focused.
264 Afterwards, the command +focus left+ is issued and it is verified that the
265 middle window now has focus.
267 Note that this is not a comprehensive test of the +focus+ command -- we would
268 have to test wrapping, focus when using a more complex layout, focusing the
269 parent/child containers, etc. But that is not the point of this testcase.
270 Instead, we just want to know if +$x->input_focus+ corresponds with what we are
271 expecting. If not, something is completely wrong with the test environment and
272 this trivial test will fail.
274 .t/11-goto.t: Test that the feature does not work (yet)
275 ----------------------
276 #####################################################################
277 # Now goto a mark which does not exist
278 #####################################################################
280 my $random_mark = mktemp('mark.XXXXXX');
282 $focus = focus_after(qq|[con_mark="$random_mark"] focus|);
283 is($focus, $mid->id, "focus unchanged");
284 ----------------------
286 In this new major section, a random mark (mark is an identifier for a window,
287 see "VIM-like marks" in the i3 User’s Guide) will be generated. Afterwards, we
288 test that trying to focus that mark will not do anything. This is important: Do
289 not only test that using a feature has the expected outcome, but also test that
290 using it without properly initializing it does no harm. This command could for
291 example have changed focus anyways (a bug) or crash i3 (obviously a bug).
293 .t/11-goto.t: Test that the feature does work
294 ----------------------
295 cmd "mark $random_mark";
297 $focus = focus_after('focus left');
298 is($focus, $top->id, "Top window focused");
300 $focus = focus_after(qq|[con_mark="$random_mark"] focus|);
301 is($focus, $mid->id, "goto worked");
302 ----------------------
304 Remember: Focus was on the middle window (we verified that earlier in "Test
305 assumptions"). We now mark the middle window with our randomly generated mark.
306 Afterwards, we switch focus away from the middle window to be able to tell if
307 focusing it via its mark will work. If it does work (next test), the goto
310 .t/11-goto.t: Test corner case
311 ----------------------
312 # check that we can specify multiple criteria
314 $focus = focus_after('focus left');
315 is($focus, $top->id, "Top window focused");
317 $focus = focus_after(qq|[con_mark="$random_mark" con_mark="$random_mark"] focus|);
318 is($focus, $mid->id, "goto worked");
319 ----------------------
321 Now we test the same feature, but specifying the mark twice in the command.
322 This should have no effect, but let’s be sure: test it and see if things go
325 .t/11-goto.t: Test second code path
326 ----------------------
327 #####################################################################
328 # Check whether the focus command will switch to a different
329 # workspace if necessary
330 #####################################################################
332 my $tmp2 = fresh_workspace;
334 is(focused_ws(), $tmp2, 'tmp2 now focused');
336 cmd qq|[con_mark="$random_mark"] focus|;
338 is(focused_ws(), $tmp, 'tmp now focused');
339 ----------------------
341 This part of the test checks that focusing windows by mark works across
342 workspaces. It uses i3test's +focused_ws+ function to get the current
345 .t/11-goto.t: Test second code path
346 ----------------------
348 ----------------------
350 The end of every testcase has to contain the +done_testing+ line. This tells
351 +complete-run.pl+ that the test was finished successfully. If it does not
352 occur, the test might have crashed during execution -- some of the reasons why
353 that could happen are bugs in the used modules, bugs in the testcase itself or
354 an i3 crash resulting in the testcase being unable to communicate with i3 via
358 == Appendix A: The i3 sync protocol
360 Consider the following situation: You open two windows in your testcase, then
361 you use +focus left+ and want to verify that the X11 focus has been updated
362 properly. Sounds simple, right? Let’s assume you use this straight-forward
365 .Racey focus testcase
367 my $left = open_window($x);
368 my $right = open_window($x);
370 is($x->input_focus, $left->id, 'left window focused');
373 However, the test fails. Sometimes. Apparantly, there is a race condition in
374 your test. If you think about it, this is because you are using two different
375 pieces of software: You tell i3 to update focus, i3 confirms that, and then you
376 ask X11 to give you the current focus. There is a certain time i3 needs to
377 update the X11 state. If the testcase gets CPU time before X11 processed i3's
378 requests, the test will fail.
380 image::i3-sync.png["Diagram of the race condition", title="Diagram of the race condition"]
382 One way to "solve" this would be to add +sleep 0.5;+ after the +cmd+ call.
383 After 0.5 seconds it should be safe to assume that focus has been updated,
386 In practice, this usually works. However, it has several problems:
388 1. This is obviously not a clean solution, but a workaround. Ugly.
389 2. On very slow machines, this might not work. Unlikely, but in different
390 situations (a delay to wait for i3 to startup) the necessary time is much
391 harder to guess, even for fast machines.
392 3. This *wastes a lot of time*. Usually, your computer is much faster than 0.5s
393 to update the status. However, sometimes, it might take 0.4s, so we can’t
396 To illustrate how grave the problem with wasting time actually is: Before
397 removing all sleeps from the testsuite, a typical run using 4 separate X
398 servers took around 50 seconds on my machine. After removing all the sleeps,
399 we achieved times of about 25 seconds. This is very significant and influences
400 the way you think about tests -- the faster they are, the more likely you are
401 to check whether everything still works quite often (which you should).
403 What I am trying to say is: Delays adds up quickly and make the test suite
406 The real solution for this problem is a mechanism which I call "the i3 sync
407 protocol". The idea is to send a request (which does not modify state) via X11
408 to i3 which will then be answered. Due to the request's position in the event
409 queue (*after* all previous events), you can be sure that by the time you
410 receive the reply, all other events have been dealt with by i3 (and, more
413 image::i3-sync-working.png["Diagram of the i3 sync solution", title="Diagram of the i3 sync solution"]
415 === Implementation details
417 The client which wants to sync with i3 initiates the protocol by sending a
418 ClientMessage to the X11 root window:
422 # Generate a ClientMessage, see xcb_client_message_t
423 my $msg = pack "CCSLLLLLLL",
424 CLIENT_MESSAGE, # response_type
427 $root, # destination window
428 $x->atom(name => 'I3_SYNC')->id,
430 $_sync_window->id, # data[0]: our own window id
431 $myrnd, # data[1]: a random value to identify the request
436 # Send it to the root window -- since i3 uses the SubstructureRedirect
437 # event mask, it will get the ClientMessage.
438 $x->send_event(0, $root, EVENT_MASK_SUBSTRUCTURE_REDIRECT, $msg);
441 i3 will then reply with the same ClientMessage, sent to the window specified in
442 +data[0]+. In the reply, +data[0]+ and +data[1]+ are exactly the same as in the
443 request. You should use a random value in +data[1]+ and check that you received
444 the same one when getting the reply.
446 == Appendix B: Socket activation