TAP(3) BSD Library Functions Manual TAP(3)NAMEtap — write tests that implement the Test Anything Protocol
SYNOPSIS
#include <tap.h>
DESCRIPTION
The tap library provides functions for writing test scripts that produce
output consistent with the Test Anything Protocol. A test harness that
parses this protocol can run these tests and produce useful reports indi‐
cating their success or failure.
PRINTF STRINGS
In the descriptions that follow, for any function that takes as the last
two parameters “char *, ...” it can be assumed that the char * is a
printf()-like format string, and the optional arguments are values to be
placed in that string.
TEST PLANS
int plan_tests(unsigned int)
int plan_no_plan(void)
int plan_skip_all(char *, ...)
You must first specify a test plan. This indicates how many tests you
intend to run, and allows the test harness to notice if any tests were
missed, or if the test program exited prematurely.
To do this, use plan_tests(), which always returns 0. The function will
cause your program to exit prematurely if you specify 0 tests.
In some situations you may not know how many tests you will be running,
or you are developing your test program, and do not want to update the
plan_tests() parameter every time you make a change. For those situa‐
tions use plan_no_plan(). It returns 0, and indicates to the test har‐
ness that an indeterminate number of tests will be run.
Both plan_tests() and plan_no_plan() will cause your test program to exit
prematurely with a diagnostic message if they are called more than once.
If your test program detects at run time that some required functionality
is missing (for example, it relies on a database connection which is not
present, or a particular configuration option that has not been included
in the running kernel) use plan_skip_all(), passing as parameters a
string to display indicating the reason for skipping the tests.
SIMPLE TESTS
unsigned int ok(expression, char *, ...)
unsigned int ok1(expression)
unsigned int pass(char *, ...)
unsigned int fail(char *, ...)
Tests are implemented as expressions checked by calls to the ok() and
ok1() macros. In both cases expression should evaluate to true if the
test succeeded.
ok() allows you to specify a name, or comment, describing the test which
will be included in the output. ok1() is for those times when the
expression to be tested is self explanatory and does not need an associ‐
ated comment. In those cases the test expression becomes the comment.
These four calls are equivalent:
int i = 5;
ok(i == 5, "i equals 5"); /* Overly verbose */
ok(i == 5, "i equals %d", i); /* Just to demonstrate printf-like
behaviour of the test name */
ok(i == 5, "i == 5"); /* Needless repetition */
ok1(i == 5); /* Just right */
It is good practice to ensure that the test name describes the meaning
behind the test rather than what you are testing. Viz
ok(db != NULL, "db is not NULL"); /* Not bad, but */
ok(db != NULL, "Database conn. succeeded"); /* this is better */
ok() and ok1() return 1 if the expression evaluated to true, and 0 if it
evaluated to false. This lets you chain calls from ok() to diag() to
only produce diagnostic output if the test failed. For example, this
code will include diagnostic information about why the database connec‐
tion failed, but only if the test failed.
ok(db != NULL, "Database conn. succeeded") ||
diag("Database error code: %d", dberrno);
You also have pass() and fail(). From the Test::More documentation:
Sometimes you just want to say that the tests have passed.
Usually the case is you've got some complicated condition
that is difficult to wedge into an ok(). In this case,
you can simply use pass() (to declare the test ok) or fail
(for not ok).
Use these very, very, very sparingly.
These are synonyms for ok(1, ...) and ok(0, ...).
SKIPPING TESTS
int skip(unsigned int, char *, ...)
skip_start(expression, unsigned int, char *, ...)
skip_end
Sets of tests can be skipped. Ordinarily you would do this because the
test can't be run in this particular testing environment.
For example, suppose some tests should be run as root. If the test is
not being run as root then the tests should be skipped. In this imple‐
mentation, skipped tests are flagged as being ok, with a special message
indicating that they were skipped. It is your responsibility to ensure
that the number of tests skipped (the first parameter to skip()) is cor‐
rect for the number of tests to skip.
One way of implementing this is with a “do { } while(0);” loop, or an
“if() { } else { }” construct, to ensure that there are no additional
side effects from the skipped tests.
if(getuid() != 0) {
skip(1, "because test only works as root");
} else {
ok(do_something_as_root() == 0, "Did something as root");
}
Two macros are provided to assist with this. The previous example could
be re-written as follows.
skip_start(getuid() != 0, 1, "because test only works as root");
ok(do_something_as_root() == 0, "Did something as root");
skip_end; /* It's a macro, no parentheses */
MARKING TESTS AS “TODO”
void todo_start(char *, ...)
void todo_end(void)
Sets of tests can be flagged as being “TODO”. These are tests that you
expect to fail, probably because you haven't fixed a bug, or finished a
new feature yet. These tests will still be run, but with additional out‐
put that indicates that they are expected to fail. Should a test start
to succeed unexpectedly, tools like prove(1) will indicate this, and you
can move the test out of the todo block. This is much more useful than
simply commenting out (or “#ifdef 0 ... #endif”) the tests.
todo_start("dwim() not returning true yet");
ok(dwim(), "Did what the user wanted");
todo_end();
Should dwim() ever start succeeding you will know about it as soon as you
run the tests. Note that unlike the skip_*() family, additional code
between todo_start() and todo_end() is executed.
SKIP vs. TODO
From the Test::More documentation;
If it's something the user might not be able to do, use SKIP.
This includes optional modules that aren't installed, running
under an OS that doesn't have some feature (like fork() or
symlinks), or maybe you need an Internet connection and one
isn't available.
If it's something the programmer hasn't done yet, use TODO.
This is for any code you haven't written yet, or bugs you have
yet to fix, but want to put tests in your testing script
(always a good idea).
DIAGNOSTIC OUTPUT
unsigned int diag(char *, ...)
If your tests need to produce diagnostic output, use diag(). It ensures
that the output will not be considered by the TAP test harness. diag()
adds the necessary trailing “\n” for you.
diag("Expected return code 0, got return code %d", rcode);
diag() always returns 0.
EXIT STATUS
int exit_status(void)
For maximum compatability your test program should return a particular
exit code. This is calculated by exit_status() so it is sufficient to
always return from main() with either “return exit_status();” or
“exit(exit_status());” as appropriate.
EXAMPLES
The tests directory in the source distribution contains numerous tests of
tap functionality, written using tap. Examine them for examples of how
to construct test suites.
COMPATABILITYtap strives to be compatible with the Perl Test::More and Test::Harness
modules. The test suite verifies that tap is bug-for-bug compatible with
their behaviour. This is why some functions which would more naturally
return nothing return constant values.
If the POSIX Threads Library (libpthread, -lpthread) is found at compile
time, tap should be thread safe. Indications to the contrary (and test
cases that expose incorrect behaviour) are very welcome.
SEE ALSOTest::More(1), Test::Harness(1), prove(1)STANDARDStap requires a ISO/IEC 9899:1999 (“ISO C99”) compiler. Some of the tap
functionality is implemented as variadic macros, and that functionality
was not formally codified until C99. Patches to use tap with earlier
compilers that have their own implementation of variadic macros will be
gratefully received.
HISTORYtap was written to help improve the quality and coverage of the FreeBSD
regression test suite, and released in the hope that others find it a
useful tool to help improve the quality of their code.
AUTHORS
Nik Clayton ⟨nik@ngo.org.uk⟩, ⟨nik@FreeBSD.org⟩
tap would not exist without the efforts of
Michael G Schwern ⟨schqern@pobox.com⟩,
Andy Lester ⟨andy@petdance.com⟩, and the countless others who have worked
on the Perl QA programme.
BUGS
Ideally, running the tests would have no side effects on the behaviour of
the application you are testing. However, it is not always possible to
avoid them. The following side effects of using tap are known.
· stdout is set to unbuffered mode after calling any of the
plan_*() functions.
BSD December 20, 2004 BSD
