1Test::MockObject(3)   User Contributed Perl Documentation  Test::MockObject(3)
2
3
4

NAME

6       Test::MockObject - Perl extension for emulating troublesome interfaces
7

SYNOPSIS

9         use Test::MockObject;
10         my $mock = Test::MockObject->new();
11         $mock->set_true( 'somemethod' );
12         ok( $mock->somemethod() );
13
14         $mock->set_true( 'veritas')
15              ->set_false( 'ficta' )
16              ->set_series( 'amicae', 'Sunny', 'Kylie', 'Bella' );
17

DESCRIPTION

19       It's a simple program that doesn't use any other modules, and those are
20       easy to test.  More often, testing a program completely means faking up
21       input to another module, trying to coax the right output from something
22       you're not supposed to be testing anyway.
23
24       Testing is a lot easier when you can control the entire environment.
25       With Test::MockObject, you can get a lot closer.
26
27       Test::MockObject allows you to create objects that conform to
28       particular interfaces with very little code.  You don't have to
29       reimplement the behavior, just the input and the output.
30
31   IMPORTANT CAVEATS
32       Before you go wild with your testing powers, consider three caveats:
33
34       •   It is possible to write highly detailed unit tests that pass even
35           when your integration tests may fail.  Testing the pieces
36           individually does not excuse you from testing the whole thing
37           together.
38
39       •   In cases where you only need to mock one or two pieces of an
40           existing module, consider Test::MockObject::Extends instead.
41
42       •   If the code under testing produces strange errors about type
43           checks, pass the "-debug" flag when using "Test::MockObject" or
44           "Test::MockObject::Extends". This will load both UNIVERSAL::isa and
45           UNIVERSAL::can to perform additional debugging on the incorrect use
46           of both methods from the UNIVERSAL package. (This behavior used to
47           be active by default, but that was, however correct, probably a
48           burden to onerous for the CPAN.)
49
50   EXPORT
51       None.
52
53   METHODS
54       The most important thing a Mock Object can do is to conform
55       sufficiently to an interface.  For example, if you're testing something
56       that relies on CGI.pm, you may find it easier to create a mock object
57       that returns controllable results at given times than to fake query
58       string input.
59
60       The Basics
61
62       •   "new"
63
64           Creates a new mock object.  By default, this is a blessed hash.
65           Pass a reference to bless that reference.
66
67               my $mock_array  = Test::MockObject->new( [] );
68               my $mock_scalar = Test::MockObject->new( \( my $scalar ) );
69               my $mock_code   = Test::MockObject->new( sub {} );
70               my $mock_glob   = Test::MockObject->new( \*GLOB );
71
72       Mocking
73
74       Your mock object is nearly useless if you don't tell it what it's
75       mocking.  This is done by installing methods.  You control the output
76       of these mocked methods.  In addition, any mocked method is tracked.
77       You can tell not only what was called, but which arguments were passed.
78       Please note that you cannot track non-mocked method calls.  They will
79       still be allowed, though Test::MockObject will carp() about them.  This
80       is considered a feature, though it may be possible to disable this in
81       the future.
82
83       As implied in the example above, it's possible to chain these calls
84       together.  Thanks to a suggestion from the fabulous Piers Cawley (CPAN
85       RT #1249), this feature came about in version 0.09.  Shorter testing
86       code is nice!
87
88       •   "mock(name, coderef [, name2, coderef2, ...])"
89
90           Adds one or more coderefs to the object.  This allows code to call
91           the named methods on the object.  For example, this code:
92
93               my $mock = Test::MockObject->new();
94               $mock->mock( 'fluorinate',
95                   sub { 'impurifying precious bodily fluids' } );
96               print $mock->fluorinate;
97
98           will print a helpful warning message.  Please note that methods are
99           only added to a single object at a time and not the class.  (There
100           is no small similarity to the Self programming language or the
101           Class::Prototyped module.)
102
103           This method forms the basis for most of Test::MockObject's testing
104           goodness.
105
106           Please Note: this method used to be add().  Due to its ambiguity,
107           it now has a different spelling.  For backwards compatibility
108           purposes, add() is available, though version 0.07 deprecated it.
109           It goes to some contortions to try to do what you mean, but I make
110           few guarantees.
111
112       •   "fake_module(module name), [ subname =" coderef, ... ]
113
114           Note: See Test::MockModule for an alternate (and better) approach.
115
116           Lies to Perl that it has already loaded a named module.  This is
117           handy when providing a mockup of a real module if you'd like to
118           prevent the actual module from interfering with the nice fakery.
119           If you're mocking Regexp::English, say:
120
121               $mock->fake_module( 'Regexp::English' );
122
123           This is both a class and as an object method.  Beware that this
124           must take place before the actual module has a chance to load.
125           Either wrap it in a BEGIN block before a use or require or place it
126           before a use_ok() or require_ok() call.
127
128           You can optionally add functions to the mocked module by passing
129           them as name => coderef pairs to fake_module().  This is handy if
130           you want to test an import():
131
132               my $import;
133               $mock->fake_module(
134                   'Regexp::English',
135                   import => sub { $import = caller }
136               );
137               use_ok( 'Regexp::Esperanto' );
138               is( $import, 'Regexp::Esperanto',
139                   'Regexp::Esperanto should use() Regexp::English' );
140
141           If you use fake_module() to mock a module that already exists in
142           memory -- one you've loaded elsewhere perhaps, but do not pass any
143           subroutines to mock, this method will throw an exception.  This is
144           because if you call the constructor later on, you probably won't
145           get a mock object back and you'll be confused.
146
147       •   "fake_new(module name)"
148
149           Note: see Test::MockObject::Extends for a better alternative to
150           this method.
151
152           Provides a fake constructor for the given module that returns the
153           invoking mock object.  Used in conjunction with fake_module(), you
154           can force the tested unit to work with the mock object instead.
155
156               $mock->fake_module( 'CGI' );
157               $mock->fake_new( 'CGI' );
158
159               use_ok( 'Some::Module' );
160               my $s = Some::Module->new();
161               is( $s->{_cgi}, $mock,
162                   'new() should create and store a new CGI object' );
163
164       •   "set_always(name, value)"
165
166           Adds a method of the specified name that always returns the
167           specified value.
168
169       •   "set_true(name_1, name_2, ... name_n)"
170
171           Adds a method of the specified name that always returns a true
172           value.  This can take a list of names.
173
174       •   "set_false(name_1, name_2, ... name_n)"
175
176           Adds a method of the specified name that always returns a false
177           value.  (Since it installs an empty subroutine, the value should be
178           false in both scalar and list contexts.)  This can take a list of
179           names.
180
181       •   "set_list(name, [ item1, item2, ... ]"
182
183           Adds a method that always returns a given list of values.  It takes
184           some care to provide a list and not an array, if that's important
185           to you.
186
187       •   "set_series(name, [ item1, item2, ... ]"
188
189           Adds a method that will return the next item in a series on each
190           call.  This can help to test error handling, by forcing a failure
191           on the first method call and then subsequent successes.  Note that
192           the series does not repeat; it will eventually run out.
193
194       •   "set_bound(name, reference)"
195
196           Adds a method bound to a variable.  Pass in a reference to a
197           variable in your test.  When you change the variable, the return
198           value of the new method will change as well.  This is often handier
199           than replacing mock methods.
200
201       •   "set_isa( name1, name2, ... namen )"
202
203           Adds an apparent parent to the module, so that calling isa() on the
204           mock will return true appropriately.  Sometimes you really need
205           this.
206
207       •   remove(name)
208
209           Removes a named method.
210
211       Checking Your Mocks
212
213       •   can( $method_name )
214
215           Returns a subroutine reference if this particular mocked object can
216           handle the named method, false otherwise.
217
218       •   isa( $class_name )
219
220           Returns true if the invocant object mocks a particular class.  You
221           must have used set_isa() first.
222
223       •   called(name)
224
225           Checks to see if something has called a named method on the object.
226           This returns a boolean value.  The current implementation does not
227           scale especially well, so use this sparingly if you need to search
228           through hundreds of calls.
229
230       •   clear()
231
232           Clears the internal record of all method calls on the object.  It's
233           handy to do this every now and then.  Note that this does not
234           affect the mocked methods, only all of the methods called on the
235           object to this point.
236
237           It's handy to clear() methods in between series of tests.  That
238           makes it much easier to call next_method() without having to skip
239           over the calls from the last set of tests.
240
241       •   "next_call([ position ])"
242
243           Returns the name and argument list of the next mocked method called
244           on an object, in list context.  In scalar context, returns only the
245           method name.  There are two important things to know about this
246           method.  First, it starts at the beginning of the call list.  If
247           your code runs like this:
248
249               $mock->set_true( 'foo' );
250               $mock->set_true( 'bar' );
251               $mock->set_true( 'baz' );
252
253               $mock->foo();
254               $mock->bar( 3, 4 );
255               $mock->foo( 1, 2 );
256
257           Then you might see output of:
258
259               my ($name, $args) = $mock->next_call();
260               print "$name (@$args)";
261
262               # prints 'foo'
263
264               $name = $mock->next_call();
265               print $name;
266
267               # prints 'bar'
268
269               ($name, $args) = $mock->next_call();
270               print "$name (@$args)";
271
272               # prints 'foo 1 2'
273
274           If you provide an optional number as the position argument, the
275           method will skip that many calls, returning the data for the last
276           one skipped.
277
278               $mock->foo();
279               $mock->bar();
280               $mock->baz();
281
282               $name = $mock->next_call();
283               print $name;
284
285               # prints 'foo'
286
287               $name = $mock->next_call( 2 );
288               print $name
289
290               # prints 'baz'
291
292           When it reaches the end of the list, it returns undef.  This is
293           probably the most convenient method in the whole module, but for
294           the sake of completeness and backwards compatibility (it takes me a
295           while to reach the truest state of laziness!), there are several
296           other methods.
297
298       •   call_pos(position)
299
300           Returns the name of the method called on the object at a specified
301           position.  This is handy if you need to test a certain order of
302           calls.  For example:
303
304               Some::Function( $mock );
305               is( $mock->call_pos(1),  'setup',
306                   'Function() should first call setup()' );
307               is( $mock->call_pos(-1), 'end',
308                   '... and last call end()' );
309
310           Positions can be positive or negative.  Please note that the first
311           position is, in fact, 1.  (This may change in the future.  I like
312           it, but am willing to reconsider.)
313
314       •   call_args(position)
315
316           Returns a list of the arguments provided to the method called at
317           the appropriate position.  Following the test above, one might say:
318
319               is( ($mock->call_args(1))[0], $mock,
320                   '... passing the object to setup()' );
321               is( scalar $mock->call_args(-1), 0,
322                   '... and no args to end()' );
323
324       •   "call_args_pos(call position, argument position)"
325
326           Returns the argument at the specified position for the method call
327           at the specified position.  One might rewrite the first test of the
328           last example as:
329
330               is( $mock->call_args_pos(1, 1), $mock,
331                   '... passing the object to setup()');
332
333       •   "call_args_string(position, [ separator ])"
334
335           Returns a stringified version of the arguments at the specified
336           position.  If no separator is given, they will not be separated.
337           This can be used as:
338
339               is( $mock->call_args_string(1), "$mock initialize",
340                   '... passing object, initialize as arguments' );
341
342       •   "called_ok(method name, [ test name ])"
343
344           Tests to see whether a method of the specified name has been called
345           on the object.  This and the following methods use Test::Builder,
346           so they integrate nicely with a test suite built around
347           Test::Simple, Test::More, or anything else compatible:
348
349               $mock->foo();
350               $mock->called_ok( 'foo' );
351
352           A generic default test name is provided.
353
354       •   "called_pos_ok(position, method name, [ test name ])"
355
356           Tests to see whether the named method was called at the specified
357           position.  A default test name is provided.
358
359       •   "called_args_pos_is(method position, argument position, expected, [
360           test name ])"
361
362           Tests to see whether the argument at the appropriate position of
363           the method in the specified position equals a specified value.  A
364           default, rather non-descript test name is provided.
365
366       •   "called_args_string_is(method position, separator, expected, [ test
367           name ])"
368
369           Joins together all of the arguments to a method at the appropriate
370           position and matches against a specified string.  A generically
371           bland test name is provided by default.  You can probably do much
372           better.
373
374       •   check_class_loaded( $class_name )
375
376           Attempts to determine whether you have a class of the given name
377           loaded and compiled.  Returns true or false.
378
379       Logging
380
381       Test::MockObject logs all mocked methods by default.  Sometimes you
382       don't want to do this.  To prevent logging all calls to a given method,
383       prepend the name of the method with "-" when mocking it.
384
385       That is:
386
387           $mock->set_true( '-foo', 'bar' );
388
389       will set mock both foo() and bar(), causing both to return true.
390       However, the object will log only calls to bar(), not foo().  To log
391       foo() again, merely mock it again without the leading "-":
392
393           $mock->set_true( 'foo' );
394
395       $mock will log all subsequent calls to foo() again.
396
397       Subclassing
398
399       There are two methods provided for subclassing:
400
401       •   "dispatch_mocked_method( $method_name, @_ )"
402
403           This method determines how to call a method (named as $method_name)
404           not available in this class.  It also controls logging.  You may or
405           may not find it useful, but I certainly take advantage of it for
406           Test::MockObject::Extends.
407
408       •   "log_call( $method_name, @_ )"
409
410           This method tracks the call of the named method and its arguments.
411

TODO

413       •   Add a factory method to avoid namespace collisions (soon)
414
415       •   Add more useful methods (catch import()?)
416

AUTHOR

418       chromatic, <chromatic at wgz dot org>
419
420       Thanks go to Curtis 'Ovid' Poe, as well as ONSITE! Technology, Inc.,
421       for finding several bugs and providing several constructive
422       suggestions.
423
424       Jay Bonci also found a false positive in called_ok().  Thanks!
425
426       Chris Winters was the first to report I'd accidentally scheduled 0.12
427       for deletion without uploading a newer version.  He also gave useful
428       feedback on Test::MockObject::Extends.
429
430       Stevan Little provided the impetus and code for set_isa().
431
432       Nicholas Clark found a documentation error.
433
434       Mutant suggested a potential problem with fake_module().
435

SEE ALSO

437       perl, Test::Tutorial, Test::More,
438       http://www.perl.com/pub/a/2001/12/04/testing.html, and
439       http://www.perl.com/pub/a/2002/07/10/tmo.html.
440
442       Copyright (c) 2002 - 2016 by chromatic <chromatic at wgz dot org>.
443
444       This program is free software; you can use, modify, and redistribute it
445       under the same terms as Perl 5.24 itself.
446
447       See http://www.perl.com/perl/misc/Artistic.html
448
449
450
451perl v5.36.0                      2023-01-20               Test::MockObject(3)
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