Provided by: libtest-mockobject-perl_1.20120301-1_all 
NAME
Test::MockObject - Perl extension for emulating troublesome interfaces
SYNOPSIS
use Test::MockObject;
my $mock = Test::MockObject->new();
$mock->set_true( 'somemethod' );
ok( $mock->somemethod() );
$mock->set_true( 'veritas')
->set_false( 'ficta' )
->set_series( 'amicae', 'Sunny', 'Kylie', 'Bella' );
DESCRIPTION
It's a simple program that doesn't use any other modules, and those are easy to test.
More often, testing a program completely means faking up input to another module, trying
to coax the right output from something you're not supposed to be testing anyway.
Testing is a lot easier when you can control the entire environment. With
Test::MockObject, you can get a lot closer.
Test::MockObject allows you to create objects that conform to particular interfaces with
very little code. You don't have to reimplement the behavior, just the input and the
output.
IMPORTANT CAVEATS
Before you go wild with your testing powers, consider three caveats:
• It is possible to write highly detailed unit tests that pass even when your
integration tests may fail. Testing the pieces individually does not excuse you from
testing the whole thing together.
• In cases where you only need to mock one or two pieces of an existing module, consider
Test::MockObject::Extends instead.
• If the code under testing produces strange errors about type checks, pass the "-debug"
flag when using "Test::MockObject" or "Test::MockObject::Extends". This will load both
UNIVERSAL::isa and UNIVERSAL::can to perform additional debugging on the incorrect use
of both methods from the UNIVERSAL package. (This behavior used to be active by
default, but that was, however correct, probably a burden to onerous for the CPAN.)
EXPORT
None.
METHODS
The most important thing a Mock Object can do is to conform sufficiently to an interface.
For example, if you're testing something that relies on CGI.pm, you may find it easier to
create a mock object that returns controllable results at given times than to fake query
string input.
The Basics
• "new"
Creates a new mock object. By default, this is a blessed hash. Pass a reference to
bless that reference.
my $mock_array = Test::MockObject->new( [] );
my $mock_scalar = Test::MockObject->new( \( my $scalar ) );
my $mock_code = Test::MockObject->new( sub {} );
my $mock_glob = Test::MockObject->new( \*GLOB );
Mocking
Your mock object is nearly useless if you don't tell it what it's mocking. This is done
by installing methods. You control the output of these mocked methods. In addition, any
mocked method is tracked. You can tell not only what was called, but which arguments were
passed. Please note that you cannot track non-mocked method calls. They will still be
allowed, though Test::MockObject will carp() about them. This is considered a feature,
though it may be possible to disable this in the future.
As implied in the example above, it's possible to chain these calls together. Thanks to a
suggestion from the fabulous Piers Cawley (CPAN RT #1249), this feature came about in
version 0.09. Shorter testing code is nice!
• "mock(name, coderef)"
Adds a coderef to the object. This allows code to call the named method on the
object. For example, this code:
my $mock = Test::MockObject->new();
$mock->mock( 'fluorinate',
sub { 'impurifying precious bodily fluids' } );
print $mock->fluorinate;
will print a helpful warning message. Please note that methods are only added to a
single object at a time and not the class. (There is no small similarity to the Self
programming language or the Class::Prototyped module.)
This method forms the basis for most of Test::MockObject's testing goodness.
Please Note: this method used to be "add()". Due to its ambiguity, it now has a
different spelling. For backwards compatibility purposes, add() is available, though
version 0.07 deprecated it. It goes to some contortions to try to do what you mean,
but I make few guarantees.
• "fake_module(module name), [ subname =" coderef, ... ]
Note: See Test::MockModule for an alternate (and better) approach.
Lies to Perl that it has already loaded a named module. This is handy when providing
a mockup of a real module if you'd like to prevent the actual module from interfering
with the nice fakery. If you're mocking Regexp::English, say:
$mock->fake_module( 'Regexp::English' );
This is both a class and as an object method. Beware that this must take place before
the actual module has a chance to load. Either wrap it in a BEGIN block before a use
or require or place it before a "use_ok()" or "require_ok()" call.
You can optionally add functions to the mocked module by passing them as name =>
coderef pairs to "fake_module()". This is handy if you want to test an "import()":
my $import;
$mock->fake_module(
'Regexp::English',
import => sub { $import = caller }
);
use_ok( 'Regexp::Esperanto' );
is( $import, 'Regexp::Esperanto',
'Regexp::Esperanto should use() Regexp::English' );
If you use "fake_module()" to mock a module that already exists in memory -- one
you've loaded elsewhere perhaps, but do not pass any subroutines to mock, this method
will throw an exception. This is because if you call the constructor later on, you
probably won't get a mock object back and you'll be confused.
• "fake_new(module name)"
Note: see Test::MockObject::Extends for a better alternative to this method.
Provides a fake constructor for the given module that returns the invoking mock
object. Used in conjunction with "fake_module()", you can force the tested unit to
work with the mock object instead.
$mock->fake_module( 'CGI' );
$mock->fake_new( 'CGI' );
use_ok( 'Some::Module' );
my $s = Some::Module->new();
is( $s->{_cgi}, $mock,
'new() should create and store a new CGI object' );
• "set_always(name, value)"
Adds a method of the specified name that always returns the specified value.
• "set_true(name_1, name_2, ... name_n)"
Adds a method of the specified name that always returns a true value. This can take a
list of names.
• "set_false(name_1, name_2, ... name_n)"
Adds a method of the specified name that always returns a false value. (Since it
installs an empty subroutine, the value should be false in both scalar and list
contexts.) This can take a list of names.
• "set_list(name, [ item1, item2, ... ]"
Adds a method that always returns a given list of values. It takes some care to
provide a list and not an array, if that's important to you.
• "set_series(name, [ item1, item2, ... ]"
Adds a method that will return the next item in a series on each call. This can help
to test error handling, by forcing a failure on the first method call and then
subsequent successes. Note that the series does not repeat; it will eventually run
out.
• "set_bound(name, reference)"
Adds a method bound to a variable. Pass in a reference to a variable in your test.
When you change the variable, the return value of the new method will change as well.
This is often handier than replacing mock methods.
• "set_isa( name1, name2, ... namen )"
Adds an apparent parent to the module, so that calling "isa()" on the mock will return
true appropriately. Sometimes you really need this.
• "remove(name)"
Removes a named method.
Checking Your Mocks
• "can( $method_name )"
Returns a subroutine reference if this particular mocked object can handle the named
method, false otherwise.
• "isa( $class_name )"
Returns true if the invocant object mocks a particular class. You must have used
"set_isa()" first.
• "called(name)"
Checks to see if something has called a named method on the object. This returns a
boolean value. The current implementation does not scale especially well, so use this
sparingly if you need to search through hundreds of calls.
• "clear()"
Clears the internal record of all method calls on the object. It's handy to do this
every now and then. Note that this does not affect the mocked methods, only all of
the methods called on the object to this point.
It's handy to "clear()" methods in between series of tests. That makes it much easier
to call "next_method()" without having to skip over the calls from the last set of
tests.
• "next_call([ position ])"
Returns the name and argument list of the next mocked method called on an object, in
list context. In scalar context, returns only the method name. There are two
important things to know about this method. First, it starts at the beginning of the
call list. If your code runs like this:
$mock->set_true( 'foo' );
$mock->set_true( 'bar' );
$mock->set_true( 'baz' );
$mock->foo();
$mock->bar( 3, 4 );
$mock->foo( 1, 2 );
Then you might see output of:
my ($name, $args) = $mock->next_call();
print "$name (@$args)";
# prints 'foo'
$name = $mock->next_call();
print $name;
# prints 'bar'
($name, $args) = $mock->next_call();
print "$name (@$args)";
# prints 'foo 1 2'
If you provide an optional number as the position argument, the method will skip that
many calls, returning the data for the last one skipped.
$mock->foo();
$mock->bar();
$mock->baz();
$name = $mock->next_call();
print $name;
# prints 'foo'
$name = $mock->next_call( 2 );
print $name
# prints 'baz'
When it reaches the end of the list, it returns undef. This is probably the most
convenient method in the whole module, but for the sake of completeness and backwards
compatibility (it takes me a while to reach the truest state of laziness!), there are
several other methods.
• "call_pos(position)"
Returns the name of the method called on the object at a specified position. This is
handy if you need to test a certain order of calls. For example:
Some::Function( $mock );
is( $mock->call_pos(1), 'setup',
'Function() should first call setup()' );
is( $mock->call_pos(-1), 'end',
'... and last call end()' );
Positions can be positive or negative. Please note that the first position is, in
fact, 1. (This may change in the future. I like it, but am willing to reconsider.)
• "call_args(position)"
Returns a list of the arguments provided to the method called at the appropriate
position. Following the test above, one might say:
is( ($mock->call_args(1))[0], $mock,
'... passing the object to setup()' );
is( scalar $mock->call_args(-1), 0,
'... and no args to end()' );
• "call_args_pos(call position, argument position)"
Returns the argument at the specified position for the method call at the specified
position. One might rewrite the first test of the last example as:
is( $mock->call_args_pos(1, 1), $mock,
'... passing the object to setup()');
• "call_args_string(position, [ separator ])"
Returns a stringified version of the arguments at the specified position. If no
separator is given, they will not be separated. This can be used as:
is( $mock->call_args_string(1), "$mock initialize",
'... passing object, initialize as arguments' );
• "called_ok(method name, [ test name ])"
Tests to see whether a method of the specified name has been called on the object.
This and the following methods use Test::Builder, so they integrate nicely with a test
suite built around Test::Simple, Test::More, or anything else compatible:
$mock->foo();
$mock->called_ok( 'foo' );
A generic default test name is provided.
• "called_pos_ok(position, method name, [ test name ])"
Tests to see whether the named method was called at the specified position. A default
test name is provided.
• "called_args_pos_is(method position, argument position, expected, [ test name ])"
Tests to see whether the argument at the appropriate position of the method in the
specified position equals a specified value. A default, rather non-descript test name
is provided.
• "called_args_string_is(method position, separator, expected, [ test name ])"
Joins together all of the arguments to a method at the appropriate position and
matches against a specified string. A generically bland test name is provided by
default. You can probably do much better.
• "check_class_loaded( $class_name )"
Attempts to determine whether you have a class of the given name loaded and compiled.
Returns true or false.
Logging
Test::MockObject logs all mocked methods by default. Sometimes you don't want to do this.
To prevent logging all calls to a given method, prepend the name of the method with "-"
when mocking it.
That is:
$mock->set_true( '-foo', 'bar' );
will set mock both "foo()" and "bar()", causing both to return true. However, the object
will log only calls to "bar()", not "foo()". To log "foo()" again, merely mock it again
without the leading "-":
$mock->set_true( 'foo' );
$mock will log all subsequent calls to "foo()" again.
Subclassing
There are two methods provided for subclassing:
• "dispatch_mocked_method( $method_name, @_ )"
This method determines how to call a method (named as $method_name) not available in
this class. It also controls logging. You may or may not find it useful, but I
certainly take advantage of it for Test::MockObject::Extends.
• "log_call( $method_name, @_ )"
This method tracks the call of the named method and its arguments.
TODO
• Add a factory method to avoid namespace collisions (soon)
• Add more useful methods (catch "import()"?)
AUTHOR
chromatic, <chromatic at wgz dot org>
Thanks go to Curtis 'Ovid' Poe, as well as ONSITE! Technology, Inc., for finding several
bugs and providing several constructive suggestions.
Jay Bonci also found a false positive in "called_ok()". Thanks!
Chris Winters was the first to report I'd accidentally scheduled 0.12 for deletion without
uploading a newer version. He also gave useful feedback on Test::MockObject::Extends.
Stevan Little provided the impetus and code for "set_isa()".
Nicholas Clark found a documentation error.
Mutant suggested a potential problem with fake_module().
SEE ALSO
perl, Test::Tutorial, Test::More, http://www.perl.com/pub/a/2001/12/04/testing.html, and
http://www.perl.com/pub/a/2002/07/10/tmo.html.
COPYRIGHT
Copyright (c) 2002 - 2011 by chromatic <chromatic at wgz dot org>.
This program is free software; you can use, modify, and redistribute it under the same
terms as Perl 5.10.x itself.
See http://www.perl.com/perl/misc/Artistic.html