Test::Tester(3perl) Perl Programmers Reference Guide Test::Tester(3perl)
NAME
Test::Tester - Ease testing test modules built with Test::Builder
SYNOPSIS
use Test::Tester tests => 6;
use Test::MyStyle;
check_test(
sub {
is_mystyle_eq("this", "that", "not eq");
},
{
ok => 0, # expect this to fail
name => "not eq",
diag => "Expected: 'this'\nGot: 'that'",
}
);
or
use Test::Tester tests => 6;
use Test::MyStyle;
check_test(
sub {
is_mystyle_qr("this", "that", "not matching");
},
{
ok => 0, # expect this to fail
name => "not matching",
diag => qr/Expected: 'this'\s+Got: 'that'/,
}
);
or
use Test::Tester;
use Test::More tests => 3;
use Test::MyStyle;
my ($premature, @results) = run_tests(
sub {
is_database_alive("dbname");
}
);
# now use Test::More::like to check the diagnostic output
like($results[0]->{diag}, "/^Database ping took \\d+ seconds$"/, "diag");
DESCRIPTION
If you have written a test module based on Test::Builder then
Test::Tester allows you to test it with the minimum of effort.
HOW TO USE (THE EASY WAY)
From version 0.08 Test::Tester no longer requires you to included
anything special in your test modules. All you need to do is
use Test::Tester;
in your test script before any other Test::Builder based modules and
away you go.
Other modules based on Test::Builder can be used to help with the
testing. In fact you can even use functions from your module to test
other functions from the same module (while this is possible it is
probably not a good idea, if your module has bugs, then using it to test
itself may give the wrong answers).
The easiest way to test is to do something like
check_test(
sub { is_mystyle_eq("this", "that", "not eq") },
{
ok => 0, # we expect the test to fail
name => "not eq",
diag => "Expected: 'this'\nGot: 'that'",
}
);
this will execute the is_mystyle_eq test, capturing its results and
checking that they are what was expected.
You may need to examine the test results in a more flexible way, for
example, the diagnostic output may be quite long or complex or it may
involve something that you cannot predict in advance like a timestamp.
In this case you can get direct access to the test results:
my ($premature, @results) = run_tests(
sub {
is_database_alive("dbname");
}
);
like($result[0]->{diag}, "/^Database ping took \\d+ seconds$"/, "diag");
or
check_test(
sub { is_mystyle_qr("this", "that", "not matching") },
{
ok => 0, # we expect the test to fail
name => "not matching",
diag => qr/Expected: 'this'\s+Got: 'that'/,
}
);
We cannot predict how long the database ping will take so we use
Test::More's like() test to check that the diagnostic string is of the
right form.
HOW TO USE (THE HARD WAY)
This is here for backwards compatibility only
Make your module use the Test::Tester::Capture object instead of the
Test::Builder one. How to do this depends on your module but assuming
that your module holds the Test::Builder object in $Test and that all
your test routines access it through $Test then providing a function
something like this
sub set_builder
{
$Test = shift;
}
should allow your test scripts to do
Test::YourModule::set_builder(Test::Tester->capture);
and after that any tests inside your module will captured.
TEST RESULTS
The result of each test is captured in a hash. These hashes are the same
as the hashes returned by Test::Builder->details but with a couple of
extra fields.
These fields are documented in Test::Builder in the details() function
ok
Did the test pass?
actual_ok
Did the test really pass? That is, did the pass come from
Test::Builder->ok() or did it pass because it was a TODO test?
name
The name supplied for the test.
type
What kind of test? Possibilities include, skip, todo etc. See
Test::Builder for more details.
reason
The reason for the skip, todo etc. See Test::Builder for more details.
These fields are exclusive to Test::Tester.
diag
Any diagnostics that were output for the test. This only includes
diagnostics output after the test result is declared.
Note that Test::Builder ensures that any diagnostics end in a \n and
it in earlier versions of Test::Tester it was essential that you have
the final \n in your expected diagnostics. From version 0.10 onward,
Test::Tester will add the \n if you forgot it. It will not add a \n if
you are expecting no diagnostics. See below for help tracking down
hard to find space and tab related problems.
depth
This allows you to check that your test module is setting the correct
value for $Test::Builder::Level and thus giving the correct file and
line number when a test fails. It is calculated by looking at caller()
and $Test::Builder::Level. It should count how many subroutines there
are before jumping into the function you are testing. So for example
in
run_tests( sub { my_test_function("a", "b") } );
the depth should be 1 and in
sub deeper { my_test_function("a", "b") }
run_tests(sub { deeper() });
depth should be 2, that is 1 for the sub {} and one for deeper(). This
might seem a little complex but if your tests look like the simple
examples in this doc then you don't need to worry as the depth will
always be 1 and that's what Test::Tester expects by default.
Note: if you do not specify a value for depth in check_test() then it
automatically compares it against 1, if you really want to skip the
depth test then pass in undef.
Note: depth will not be correctly calculated for tests that run from a
signal handler or an END block or anywhere else that hides the call
stack.
Some of Test::Tester's functions return arrays of these hashes, just
like Test::Builder->details. That is, the hash for the first test will
be array element 1 (not 0). Element 0 will not be a hash it will be a
string which contains any diagnostic output that came before the first
test. This should usually be empty, if it's not, it means something
output diagnostics before any test results showed up.
SPACES AND TABS
Appearances can be deceptive, especially when it comes to emptiness. If
you are scratching your head trying to work out why Test::Tester is
saying that your diagnostics are wrong when they look perfectly right
then the answer is probably whitespace. From version 0.10 on,
Test::Tester surrounds the expected and got diag values with single
quotes to make it easier to spot trailing whitespace. So in this example
# Got diag (5 bytes):
# 'abcd '
# Expected diag (4 bytes):
# 'abcd'
it is quite clear that there is a space at the end of the first string.
Another way to solve this problem is to use colour and inverse video on
an ANSI terminal, see below COLOUR below if you want this.
Unfortunately this is sometimes not enough, neither colour nor quotes
will help you with problems involving tabs, other non-printing
characters and certain kinds of problems inherent in Unicode. To deal
with this, you can switch Test::Tester into a mode whereby all "tricky"
characters are shown as \{xx}. Tricky characters are those with ASCII
code less than 33 or higher than 126. This makes the output more
difficult to read but much easier to find subtle differences between
strings. To turn on this mode either call show_space() in your test
script or set the "TESTTESTERSPACE" environment variable to be a true
value. The example above would then look like
# Got diag (5 bytes):
# abcd\x{20}
# Expected diag (4 bytes):
# abcd
COLOUR
If you prefer to use colour as a means of finding tricky whitespace
characters then you can set the "TESTTESTCOLOUR" environment variable to
a comma separated pair of colours, the first for the foreground, the
second for the background. For example "white,red" will print white text
on a red background. This requires the Term::ANSIColor module. You can
specify any colour that would be acceptable to the
Term::ANSIColor::color function.
If you spell colour differently, that's no problem. The
"TESTTESTERCOLOR" variable also works (if both are set then the British
spelling wins out).
EXPORTED FUNCTIONS
($premature, @results) = run_tests(\&test_sub)
\&test_sub is a reference to a subroutine.
run_tests runs the subroutine in $test_sub and captures the results of
any tests inside it. You can run more than 1 test inside this subroutine
if you like.
$premature is a string containing any diagnostic output from before the
first test.
@results is an array of test result hashes.
cmp_result(\%result, \%expect, $name)
\%result is a ref to a test result hash.
\%expect is a ref to a hash of expected values for the test result.
cmp_result compares the result with the expected values. If any
differences are found it outputs diagnostics. You may leave out any
field from the expected result and cmp_result will not do the comparison
of that field.
cmp_results(\@results, \@expects, $name)
\@results is a ref to an array of test results.
\@expects is a ref to an array of hash refs.
cmp_results checks that the results match the expected results and if
any differences are found it outputs diagnostics. It first checks that
the number of elements in \@results and \@expects is the same. Then it
goes through each result checking it against the expected result as in
cmp_result() above.
($premature, @results) = check_tests(\&test_sub, \@expects, $name)
\&test_sub is a reference to a subroutine.
\@expect is a ref to an array of hash refs which are expected test
results.
check_tests combines run_tests and cmp_tests into a single call. It also
checks if the tests died at any stage.
It returns the same values as run_tests, so you can further examine the
test results if you need to.
($premature, @results) = check_test(\&test_sub, \%expect, $name)
\&test_sub is a reference to a subroutine.
\%expect is a ref to an hash of expected values for the test result.
check_test is a wrapper around check_tests. It combines run_tests and
cmp_tests into a single call, checking if the test died. It assumes that
only a single test is run inside \&test_sub and include a test to make
sure this is true.
It returns the same values as run_tests, so you can further examine the
test results if you need to.
show_space()
Turn on the escaping of characters as described in the SPACES AND TABS
section.
HOW IT WORKS
Normally, a test module (let's call it Test:MyStyle) calls
Test::Builder->new to get the Test::Builder object. Test::MyStyle calls
methods on this object to record information about test results. When
Test::Tester is loaded, it replaces Test::Builder's new() method with
one which returns a Test::Tester::Delegate object. Most of the time this
object behaves as the real Test::Builder object. Any methods that are
called are delegated to the real Test::Builder object so everything
works perfectly. However once we go into test mode, the method calls
are no longer passed to the real Test::Builder object, instead they go
to the Test::Tester::Capture object. This object seems exactly like the
real Test::Builder object, except, instead of outputting test results
and diagnostics, it just records all the information for later analysis.
CAVEATS
Support for calling Test::Builder->note is minimal. It's implemented as
an empty stub, so modules that use it will not crash but the calls are
not recorded for testing purposes like the others. Patches welcome.
SEE ALSO
Test::Builder the source of testing goodness. Test::Builder::Tester for
an alternative approach to the problem tackled by Test::Tester -
captures the strings output by Test::Builder. This means you cannot get
separate access to the individual pieces of information and you must
predict exactly what your test will output.
AUTHOR
This module is copyright 2005 Fergal Daly <fergal@esatclear.ie>, some
parts are based on other people's work.
Plan handling lifted from Test::More. written by Michael G Schwern
<schwern@pobox.com>.
Test::Tester::Capture is a cut down and hacked up version of
Test::Builder. Test::Builder was written by chromatic
<chromatic@wgz.org> and Michael G Schwern <schwern@pobox.com>.
LICENSE
Under the same license as Perl itself
See <https://dev.perl.org/licenses/>
perl v5.40.1 2026-08-30 Test::Tester(3perl)
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