Provided by: libtest-assertions-perl_1.054-3_all bug


       Test::Assertions::Manual - A guide to using Test::Assertions


       This is a brief guide to how you can use the Test::Assertions module in your code and test
       scripts.  The "Test::Assertions" documentation has a comprehensive list of options.

Unit testing

       To use Test::Assertions for unit testing, import it with the argument "test":

               use Test::Assertions qw(test);

       The output of Test::Assertions in test mode is suitable for collation with Test::Harness.
       Only the ASSERT() and plan() routines can create any output - all the other routines
       simply return values.

   Planning tests
       Test::Assertions offers a "plan tests" syntax similar to Test::More:

               plan tests => 42;
               # Which creates the output:

       If you find having to increment the number at the top of your test script every time you
       add a test irritating, you can use the automatic, Do What I Mean, form:

               plan tests;

       In this case, Test::Assertions will read your code and count the number of ASSERT
       statements and use this for the expected number of tests.  A caveat is that it expects all
       your ASSERT statements to be executed once only, hence ASSERTs in if and foreach blocks
       will fool Test::Assertions and you'll have to maintain the count manually in these cases.
       Furthermore, it uses caller() to get the filename of the code so it may not work if you
       invoke your program with a relative filename and then change working directory before
       calling this automatic "plan tests;" form.

       Test::Assertions offers a couple of additional functions - only() and ignore() to control
       which tests will be reported.  Usage is as follows:

               ignore(2, 5) if($^O eq 'MsWin32');
               only(1..10) unless($^O eq 'MsWin32');

       Note that these won't stop the actual test code from being attempted, but the results
       won't be reported.

   Testing things
       The routines for constructing tests are deliberately ALL CAPS so you can discriminate at a
       glance between the test and what is being tested.  To check something does what expected,
       use ASSERT:

               ASSERT(1 == 1);

       This gives the output:

               ok 1

       An optional 2nd arg may be supplied for a comment to label the test:

               ASSERT(1 == 1, "an example test");

       This gives the output:

               ok 1 (an example test)

       In the interest of brevity of documentation, I'll omit the 2nd argument from my examples
       below.  For your real-world tests, labelling the output is strongly recommended so when
       something fails you know what it is.

       If you are hopelessly addicted to invoking your tests with an ok() routine,
       Test::Assertions has a concession for Test::Simple/More junkies:

               use Test::Assertions qw(test/ok);
               plan tests => 1;
               ok(1, "ok() works just like ASSERT()");

   More complex tests with helper routines
       Most real-world unit tests will need to check data structures returned from an API.  The
       EQUAL() function compares two data structures deeply (a bit like Test::More's eq_array or

               ASSERT( EQUAL(\@arr, [1,2,3]) );
               ASSERT( EQUAL(\%observed, \%expected) );

       For routines that return large strings or write to files (e.g. templating), you might want
       to have your expected output held externally in a file.  Test::Assertions provides a few
       routines to make this easy.  EQUALS_FILE compares a string to the contents of a file:

               ASSERT( EQUALS_FILE($returned, "expected.txt") );

       Whereas FILES_EQUAL compares the contents of 2 files:

               ASSERT( FILES_EQUAL("observed.txt", "expected.txt") );
               unlink("observed.txt"); #always clean up so state on 2nd run is same as 1st run

       If your files contain serialized data structures, e.g. the output of Data::Dumper, you may
       wish to use do(), or eval() their contents, and use the EQUAL() routine to compare the
       structures, rather than comparing the serialized forms directly.

               my $var1 = do('file1.datadump');
               my $var2 = do('file2.datadump');
               ASSERT( EQUAL($var1, $var2), 'serialized versions matched' );

       The MATCHES_FILE routine compares a string with regex that is read from a file, which is
       most useful if your string contains dates, timestamps, filepaths, or other items which
       might change from one run of the test to the next, or across different machines:

               ASSERT( MATCHES_FILE($string_to_examine, "expected.regex.txt") );

       Another thing you are likely to want to test is code raising exceptions with die().  The
       DIED() function confirms if a coderef raises an exception:

               ASSERT( DIED(
                       sub {

       The DIED routine doesn't clobber $@, so you can use this in your test description:

               ASSERT( DIED(
                       sub {
               ), "raises an exception - " . (chomp $@, $@));

       Occasionally you'll want to check if a perl script simply compiles.  Whilst this is no
       substitute for writing a proper unit test for the script, sometimes it's useful:

               ASSERT( COMPILES("") );

       An optional second argument forces the code to be compiled under 'strict':

               ASSERT( COMPILES("", 1) );

       (normally you'll have this in your script anyway).

   Aggregating other tests together
       For complex systems you may have a whole tree of unit tests, corresponding to different
       areas of functionality of the system.  For example, there may be a set of tests
       corresponding to the expression evaluation sublanguage within a templating system.
       Rather than simply aggregating everything with Test::Harness in one flat list, you may
       want to aggregate each subtree of related functionality so that the Test::Harness
       summarisation is across these higher-level units.

       Test::Assertions provides two functions to aggregate the output of other tests.  These
       work on result strings (starting with "ok" or "not ok").  ASSESS is the lower-level
       routine working directly on result strings, ASSESS_FILE runs a unit test script and parses
       the output.  In a scalar context they return a summary result string:

               @results = ('ok 1', 'not ok 2', 'A comment', 'ok 3');
               print scalar ASSESS(\@results);

       would result in something like:

               not ok (1 errors in 3 tests)

       This output is of course a suitable input to ASSESS so complex hierarchies may be created.
       In an array context, they return a boolean value and a description which is suitable for
       feeding into ASSERT (although ASSERT's $;$ prototype means it will ignore the description)

               ASSERT ASSESS_FILE("expr/set_1.t");
               ASSERT ASSESS_FILE("expr/set_2.t");
               ASSERT ASSESS_FILE("expr/set_3.t");

       would generate output such as:

               ok 1
               ok 2
               ok 3

       Finally Test::Assertions provides a helper routine to interpret result strings:

               ($bool, $description) = INTERPRET("not ok 4 (test four)");

       would result in:

               $bool = 0;
               $description = "test four";

       which might be useful for writing your own custom collation code.

Using Test::Assertions for run-time checking

       C programmers often use ASSERT macros to trap runtime "should never happen" errors in
       their code.  You can use Test::Assertions to do this:

               use Test::Assertions qq(die);
               $rv = some_function();
               ASSERT($rv == 0, "some_function returned a non-zero value");

       You can also import Test::Assertions with warn rather than die so that the code continues

               use constant ASSERTIONS_MODE => $ENV{ENVIRONMENT} eq 'production'? 'warn' : 'die';
               use Test::Assertions(ASSERTIONS_MODE);

       Environment variables provide a nice way of switching compile-time behaviour from outside
       the process.

   Minimising overhead
       Importing Test::Assertions with no arguments results in ASSERT statements doing nothing,
       but unlike ASSERT macros in C where the preprocessor filters this out before compilation,
       there are 2 types of residual overhead:

       Runtime overhead
           When Test::Assertions is imported with no arguments, the ASSERT statement is aliased
           to an empty sub.  There is a small overhead in executing this.  In practice, unless
           you do an ASSERT on every other line, or in a performance-critical loop, you're
           unlikely to notice the overhead compared to the other work that your code is doing.

       Compilation overhead
           The Test::Assertions module must be compiled even when it is imported with no
           arguments.  Test::Assertions loads its helper modules on demand and avoids using
           pragmas to minimise its compilation overhead.  Currently Test::Assertions does not go
           to more extreme measures to cut its compilation overhead in the interests of
           maintainability and ease of installation.

       Both can be minimised by using a constant:

               use constant ENABLE_ASSERTIONS => $ENV{ENABLE_ASSERTIONS};

               #Minimise compile-time overhead
               if(ENABLE_ASSERTIONS) {
                       require Test::Assertions;
                       import Test::Assertions qq(die);

               $rv = some_function();

               #Eliminate runtime overhead
               ASSERT($rv == 0, "some_function returned a non-zero value") if(ENABLE_ASSERTIONS);

       Unlike Carp::Assert, Test::Assertions does not come with a "built-in" constant (DEBUG in
       the case of Carp::Assert).  Define your own constant, attach it to your own compile-time
       logic (e.g. env vars) and call it whatever you like.

   How expensive is a null ASSERT?
       Here's an indication of the overhead of calling ASSERT when Test::Assertions is imported
       with no arguments.  A comparison is included with Carp::Assert just to show that it's in
       the same ballpark - we are not advocating one module over the other.  As outlined above,
       using a constant to disable assertions is recommended in performance-critical code.


               use Benchmark;
               use Test::Assertions;
               use Carp::Assert;
               use constant ENABLE_ASSERTIONS => 0;

               #Compare null ASSERT to simple linear algebra statement
               timethis(1e6, sub{
                       ASSERT(1); #Test::Assertions
               timethis(1e6, sub{
                       assert(1); #Carp::Assert
               timethis(1e6, sub{
                       ASSERT(1) if ENABLE_ASSERTIONS;
               timethis(1e6, sub{
                       $x=$x*2 + 3;

       Results on Sun E250 (with 2x400Mhz CPUs) running perl 5.6.1 on solaris 9:

               Test::Assertions:           timethis 1000000:  3 wallclock secs ( 3.88 usr +  0.00 sys =  3.88 CPU) @ 257731.96/s (n=1000000)
               Carp::Assert:               timethis 1000000:  6 wallclock secs ( 6.08 usr +  0.00 sys =  6.08 CPU) @ 164473.68/s (n=1000000)
               Test::Assertions + const:   timethis 1000000: -1 wallclock secs ( 0.07 usr +  0.00 sys =  0.07 CPU) @ 14285714.29/s (n=1000000) (warning: too few iterations for a reliable count)
               some algebra:               timethis 1000000:  1 wallclock secs ( 2.50 usr +  0.00 sys =  2.50 CPU) @ 400000.00/s (n=1000000)

       Results for 1.7Ghz pentium M running activestate perl 5.6.1 on win XP:

               Test::Assertions:           timethis 1000000:  0 wallclock secs ( 0.42 usr +  0.00 sys =  0.42 CPU) @ 2380952.38/s (n=1000000)
               Carp::Assert:               timethis 1000000:  0 wallclock secs ( 0.57 usr +  0.00 sys =  0.57 CPU) @ 1751313.49/s (n=1000000)
               Test::Assertions + const:   timethis 1000000: -1 wallclock secs (-0.02 usr +  0.00 sys = -0.02 CPU) @ -50000000.00/s (n=1000000) (warning: too few iterations for a reliable count)
               some algebra:               timethis 1000000:  0 wallclock secs ( 0.50 usr +  0.00 sys =  0.50 CPU) @ 1996007.98/s (n=1000000)

   How significant is the compile-time overhead?
       Here's an indication of the compile-time overhead for Test::Assertions v1.050 and
       Carp::Assert v0.18.  The cost of running import() is also included.


               use Benchmark;
               use lib qw(../lib);

               timethis(3e2, sub {
                       require Test::Assertions;
                       delete $INC{"Test/"};

               timethis(3e2, sub {
                       require Test::Assertions;
                       import Test::Assertions;
                       delete $INC{"Test/"};

               timethis(3e2, sub {
                       require Carp::Assert;
                       delete $INC{"Carp/"};

               timethis(3e2, sub {
                       require Carp::Assert;
                       import Carp::Assert;
                       delete $INC{"Carp/"};

       Results on Sun E250 (with 2x400Mhz CPUs) running perl 5.6.1 on solaris 9:

               Test::Assertions:           timethis 300:  6 wallclock secs ( 6.19 usr +  0.10 sys =  6.29 CPU) @ 47.69/s (n=300)
               Test::Assertions + import:  timethis 300:  7 wallclock secs ( 6.56 usr +  0.03 sys =  6.59 CPU) @ 45.52/s (n=300)
               Carp::Assert:               timethis 300:  3 wallclock secs ( 2.47 usr +  0.32 sys =  2.79 CPU) @ 107.53/s (n=300)
               Carp::Assert + import:      timethis 300: 41 wallclock secs (40.58 usr +  0.32 sys = 40.90 CPU) @  7.33/s (n=300)

       Results for 1.7Ghz pentium M running activestate perl 5.6.1 on win XP:

               Test::Assertions:           timethis 300:  2 wallclock secs ( 1.45 usr +  0.21 sys =  1.66 CPU) @ 180.51/s (n=300)
               Test::Assertions + import:  timethis 300:  2 wallclock secs ( 1.58 usr +  0.29 sys =  1.87 CPU) @ 160.26/s (n=300)
               Carp::Assert:               timethis 300:  1 wallclock secs ( 0.99 usr +  0.26 sys =  1.25 CPU) @ 239.62/s (n=300)
               Carp::Assert + import:      timethis 300:  6 wallclock secs ( 5.42 usr +  0.38 sys =  5.80 CPU) @ 51.74/s (n=300)

       If using a constant to control compilation is not to your liking, you may want to
       experiment with SelfLoader or AutoLoader to cut down the compilation overhead further by
       delaying compilation of some of the subroutines in Test::Assertions (see SelfLoader and
       AutoLoader for more information) until the first time they are used.


       $Revision: 1.10 $ on $Date: 2005/05/04 15:56:39 $


       John Alden <cpan _at_ bbc _dot_ co _dot_ uk>