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<h1>Mock objects documentation</h1>
This page...
<ul>
<li>
<a href="#what">What are mock objects?</a>
</li>
<li>
<a href="#creation">Creating mock objects</a>.
</li>
<li>
<a href="#expectations">Mocks as critics</a> with expectations.
</li>
</ul>
<div class="content">
<h2>
<a class="target" name="what"></a>What are mock objects?</h2>
<p>
Mock objects have two roles during a test case: actor and critic.
</p>
<p>
The actor behaviour is to simulate objects that are difficult to
set up or time consuming to set up for a test.
The classic example is a database connection.
Setting up a test database at the start of each test would slow
testing to a crawl and would require the installation of the
database engine and test data on the test machine.
If we can simulate the connection and return data of our
choosing we not only win on the pragmatics of testing, but can
also feed our code spurious data to see how it responds.
We can simulate databases being down or other extremes
without having to create a broken database for real.
In other words, we get greater control of the test environment.
</p>
<p>
If mock objects only behaved as actors they would simply be
known as "server stubs".
This was originally a pattern named by Robert Binder (<a href="">Testing
object-oriented systems</a>: models, patterns, and tools,
Addison-Wesley) in 1999.
</p>
<p>
A server stub is a simulation of an object or component.
It should exactly replace a component in a system for test
or prototyping purposes, but remain lightweight.
This allows tests to run more quickly, or if the simulated
class has not been written, to run at all.
</p>
<p>
However, the mock objects not only play a part (by supplying chosen
return values on demand) they are also sensitive to the
messages sent to them (via expectations).
By setting expected parameters for a method call they act
as a guard that the calls upon them are made correctly.
If expectations are not met they save us the effort of
writing a failed test assertion by performing that duty on our
behalf.
</p>
<p>
In the case of an imaginary database connection they can
test that the query, say SQL, was correctly formed by
the object that is using the connection.
Set them up with fairly tight expectations and you will
hardly need manual assertions at all.
</p>
<h2>
<a class="target" name="creation"></a>Creating mock objects</h2>
<p>
All we need is an existing class or interface, say a database connection
that looks like this...
<pre>
<strong>class DatabaseConnection {
function DatabaseConnection() { }
function query($sql) { }
function selectQuery($sql) { }
}</strong>
</pre>
To create a mock version of the class we need to run a
code generator...
<pre>
require_once('simpletest/autorun.php');
require_once('database_connection.php');
<strong>Mock::generate('DatabaseConnection');</strong>
</pre>
This code generates a clone class called
<span class="new_code">MockDatabaseConnection</span>.
This new class appears to be the same, but actually has no behaviour at all.
</p>
<p>
The new class is usually a subclass of <span class="new_code">DatabaseConnection</span>.
Unfortunately, there is no way to create a mock version of a
class with a <span class="new_code">final</span> method without having a living version of
that method.
We consider that unsafe.
If the target is an interface, or if <span class="new_code">final</span> methods are
present in a target class, then a whole new class
is created, but one implemeting the same interfaces.
If you try to pass this separate class through a type hint that specifies
the old concrete class name, it will fail.
Code like that insists on type hinting to a class with <span class="new_code">final</span>
methods probably cannot be safely tested with mocks.
</p>
<p>
If you want to see the generated code, then simply <span class="new_code">print</span>
the output of <span class="new_code">Mock::generate()</span>.
Here is the generated code for the <span class="new_code">DatabaseConnection</span>
class rather than the interface version...
<pre>
class MockDatabaseConnection extends DatabaseConnection {
public $mock;
protected $mocked_methods = array('databaseconnection', 'query', 'selectquery');
function MockDatabaseConnection() {
$this-&gt;mock = new SimpleMock();
$this-&gt;mock-&gt;disableExpectationNameChecks();
}
...
function DatabaseConnection() {
$args = func_get_args();
$result = &amp;$this-&gt;mock-&gt;invoke("DatabaseConnection", $args);
return $result;
}
function query($sql) {
$args = func_get_args();
$result = &amp;$this-&gt;mock-&gt;invoke("query", $args);
return $result;
}
function selectQuery($sql) {
$args = func_get_args();
$result = &amp;$this-&gt;mock-&gt;invoke("selectQuery", $args);
return $result;
}
}
</pre>
Your output may vary depending on the exact version
of SimpleTest you are using.
</p>
<p>
Besides the original methods of the class, you will see some extra
methods that help testing.
More on these later.
</p>
<p>
We can now create instances of the new class within
our test case...
<pre>
require_once('simpletest/autorun.php');
require_once('database_connection.php');
Mock::generate('DatabaseConnection');
class MyTestCase extends UnitTestCase {
function testSomething() {
<strong>$connection = new MockDatabaseConnection();</strong>
}
}
</pre>
The mock version now has all the methods of the original.
Also, any type hints will be faithfully preserved.
Say our query methods expect a <span class="new_code">Query</span> object...
<pre>
<strong>class DatabaseConnection {
function DatabaseConnection() { }
function query(Query $query) { }
function selectQuery(Query $query) { }
}</strong>
</pre>
If we now pass the wrong type of object, or worse a non-object...
<pre>
class MyTestCase extends UnitTestCase {
function testSomething() {
$connection = new MockDatabaseConnection();
$connection-&gt;query('insert into accounts () values ()');
}
}
</pre>
...the code will throw a type violation at you just as the
original class would.
</p>
<p>
The mock version now has all the methods of the original.
Unfortunately, they all return <span class="new_code">null</span>.
As methods that always return <span class="new_code">null</span> are not that useful,
we need to be able to set them to something else...
</p>
<p>
<a class="target" name="stub"><h2>Mocks as actors</h2></a>
</p>
<p>
Changing the return value of a method from <span class="new_code">null</span>
to something else is pretty easy...
<pre>
<strong>$connection-&gt;returns('query', 37)</strong>
</pre>
Now every time we call
<span class="new_code">$connection-&gt;query()</span> we get
the result of 37.
There is nothing special about 37.
The return value can be arbitrarily complicated.
</p>
<p>
Parameters are irrelevant here, we always get the same
values back each time once they have been set up this way.
That may not sound like a convincing replica of a
database connection, but for the half a dozen lines of
a test method it is usually all you need.
</p>
<p>
Things aren't always that simple though.
One common problem is iterators, where constantly returning
the same value could cause an endless loop in the object
being tested.
For these we need to set up sequences of values.
Let's say we have a simple iterator that looks like this...
<pre>
class Iterator {
function Iterator() { }
function next() { }
}
</pre>
This is about the simplest iterator you could have.
Assuming that this iterator only returns text until it
reaches the end, when it returns false, we can simulate it
with...
<pre>
Mock::generate('Iterator');
class IteratorTest extends UnitTestCase() {
function testASequence() {<strong>
$iterator = new MockIterator();
$iterator-&gt;returns('next', false);
$iterator-&gt;returnsAt(0, 'next', 'First string');
$iterator-&gt;returnsAt(1, 'next', 'Second string');</strong>
...
}
}
</pre>
When <span class="new_code">next()</span> is called on the
<span class="new_code">MockIterator</span> it will first return "First string",
on the second call "Second string" will be returned
and on any other call <span class="new_code">false</span> will
be returned.
The sequenced return values take precedence over the constant
return value.
The constant one is a kind of default if you like.
</p>
<p>
Another tricky situation is an overloaded
<span class="new_code">get()</span> operation.
An example of this is an information holder with name/value pairs.
Say we have a configuration class like...
<pre>
class Configuration {
function Configuration() { ... }
function get($key) { ... }
}
</pre>
This is a likely situation for using mock objects, as
actual configuration will vary from machine to machine and
even from test to test.
The problem though is that all the data comes through the
<span class="new_code">get()</span> method and yet
we want different results for different keys.
Luckily the mocks have a filter system...
<pre>
<strong>$config = &amp;new MockConfiguration();
$config-&gt;returns('get', 'primary', array('db_host'));
$config-&gt;returns('get', 'admin', array('db_user'));
$config-&gt;returns('get', 'secret', array('db_password'));</strong>
</pre>
The extra parameter is a list of arguments to attempt
to match.
In this case we are trying to match only one argument which
is the look up key.
Now when the mock object has the
<span class="new_code">get()</span> method invoked
like this...
<pre>
$config-&gt;get('db_user')
</pre>
...it will return "admin".
It finds this by attempting to match the calling arguments
to its list of returns one after another until
a complete match is found.
</p>
<p>
You can set a default argument argument like so...
<pre><strong>
$config-&gt;returns('get', false, array('*'));</strong>
</pre>
This is not the same as setting the return value without
any argument requirements like this...
<pre><strong>
$config-&gt;returns('get', false);</strong>
</pre>
In the first case it will accept any single argument,
but exactly one is required.
In the second case any number of arguments will do and
it acts as a catchall after all other matches.
Note that if we add further single parameter options after
the wildcard in the first case, they will be ignored as the wildcard
will match first.
With complex parameter lists the ordering could be important
or else desired matches could be masked by earlier wildcard
ones.
Declare the most specific matches first if you are not sure.
</p>
<p>
There are times when you want a specific reference to be
dished out by the mock rather than a copy or object handle.
This a rarity to say the least, but you might be simulating
a container that can hold primitives such as strings.
For example...
<pre>
class Pad {
function Pad() { }
function &amp;note($index) { }
}
</pre>
In this case you can set a reference into the mock's
return list...
<pre>
function testTaskReads() {
$note = 'Buy books';
$pad = new MockPad();
$vector-&gt;<strong>returnsByReference(</strong>'note', $note, array(3)<strong>)</strong>;
$task = new Task($pad);
...
}
</pre>
With this arrangement you know that every time
<span class="new_code">$pad-&gt;note(3)</span> is
called it will return the same <span class="new_code">$note</span> each time,
even if it get's modified.
</p>
<p>
These three factors, timing, parameters and whether to copy,
can be combined orthogonally.
For example...
<pre>
$buy_books = 'Buy books';
$write_code = 'Write code';
$pad = new MockPad();
$vector-&gt;<strong>returnsByReferenceAt(0, 'note', $buy_books, array('*', 3));</strong>
$vector-&gt;<strong>returnsByReferenceAt(1, 'note', $write_code, array('*', 3));</strong>
</pre>
This will return a reference to <span class="new_code">$buy_books</span> and
then to <span class="new_code">$write_code</span>, but only if two parameters
were set the second of which must be the integer 3.
That should cover most situations.
</p>
<p>
A final tricky case is one object creating another, known
as a factory pattern.
Suppose that on a successful query to our imaginary
database, a result set is returned as an iterator, with
each call to the the iterator's <span class="new_code">next()</span> giving
one row until false.
This sounds like a simulation nightmare, but in fact it can all
be mocked using the mechanics above...
<pre>
Mock::generate('DatabaseConnection');
Mock::generate('ResultIterator');
class DatabaseTest extends UnitTestCase {
function testUserFinderReadsResultsFromDatabase() {<strong>
$result = new MockResultIterator();
$result-&gt;returns('next', false);
$result-&gt;returnsAt(0, 'next', array(1, 'tom'));
$result-&gt;returnsAt(1, 'next', array(3, 'dick'));
$result-&gt;returnsAt(2, 'next', array(6, 'harry'));
$connection = new MockDatabaseConnection();
$connection-&gt;returns('selectQuery', $result);</strong>
$finder = new UserFinder(<strong>$connection</strong>);
$this-&gt;assertIdentical(
$finder-&gt;findNames(),
array('tom', 'dick', 'harry'));
}
}
</pre>
Now only if our
<span class="new_code">$connection</span> is called with the
<span class="new_code">query()</span> method will the
<span class="new_code">$result</span> be returned that is
itself exhausted after the third call to <span class="new_code">next()</span>.
This should be enough
information for our <span class="new_code">UserFinder</span> class,
the class actually
being tested here, to come up with goods.
A very precise test and not a real database in sight.
</p>
<p>
We could refine this test further by insisting that the correct
query is sent...
<pre>
$connection-&gt;returns('selectQuery', $result, array(<strong>'select name, id from people'</strong>));
</pre>
This is actually a bad idea.
</p>
<p>
We have a <span class="new_code">UserFinder</span> in object land, talking to
database tables using a large interface - the whole of SQL.
Imagine that we have written a lot of tests that now depend
on the exact SQL string passed.
These queries could change en masse for all sorts of reasons
not related to the specific test.
For example the quoting rules could change, a table name could
change, a link table added or whatever.
This would require the rewriting of every single test any time
one of these refactoring is made, yet the intended behaviour has
stayed the same.
Tests are supposed to help refactoring, not hinder it.
I'd certainly like to have a test suite that passes while I change
table names.
</p>
<p>
As a rule it is best not to mock a fat interface.
</p>
<p>
By contrast, here is the round trip test...
<pre>
class DatabaseTest extends UnitTestCase {<strong>
function setUp() { ... }
function tearDown() { ... }</strong>
function testUserFinderReadsResultsFromDatabase() {
$finder = new UserFinder(<strong>new DatabaseConnection()</strong>);
$finder-&gt;add('tom');
$finder-&gt;add('dick');
$finder-&gt;add('harry');
$this-&gt;assertIdentical(
$finder-&gt;findNames(),
array('tom', 'dick', 'harry'));
}
}
</pre>
This test is immune to schema changes.
It will only fail if you actually break the functionality, which
is what you want a test to do.
</p>
<p>
The catch is those <span class="new_code">setUp()</span> and <span class="new_code">tearDown()</span>
methods that we've rather glossed over.
They have to clear out the database tables and ensure that the
schema is defined correctly.
That can be a chunk of extra work, but you usually have this code
lying around anyway for deployment purposes.
</p>
<p>
One place where you definitely need a mock is simulating failures.
Say the database goes down while <span class="new_code">UserFinder</span> is doing
it's work.
Does <span class="new_code">UserFinder</span> behave well...?
<pre>
class DatabaseTest extends UnitTestCase {
function testUserFinder() {
$connection = new MockDatabaseConnection();<strong>
$connection-&gt;throwOn('selectQuery', new TimedOut('Ouch!'));</strong>
$alert = new MockAlerts();<strong>
$alert-&gt;expectOnce('notify', 'Database is busy - please retry');</strong>
$finder = new UserFinder($connection, $alert);
$this-&gt;assertIdentical($finder-&gt;findNames(), array());
}
}
</pre>
We've passed the <span class="new_code">UserFinder</span> an <span class="new_code">$alert</span>
object.
This is going to do some kind of pretty notifications in the
user interface in the event of an error.
We'd rather not sprinkle our code with hard wired <span class="new_code">print</span>
statements if we can avoid it.
Wrapping the means of output means we can use this code anywhere.
It also makes testing easier.
</p>
<p>
To pass this test, the finder has to write a nice user friendly
message to <span class="new_code">$alert</span>, rather than propogating the exception.
So far, so good.
</p>
<p>
How do we get the mock <span class="new_code">DatabaseConnection</span> to throw an exception?
We generate the exception using the <span class="new_code">throwOn</span> method
on the mock.
</p>
<p>
Finally, what if the method you want to simulate does not exist yet?
If you set a return value on a method that is not there, SimpleTest
will throw an error.
What if you are using <span class="new_code">__call()</span> to simulate dynamic methods?
</p>
<p>
Objects with dynamic interfaces, using <span class="new_code">__call</span>, can
be problematic with the current mock objects implementation.
You can mock the <span class="new_code">__call()</span> method, but this is ugly.
Why should a test know anything about such low level implementation details?
It just wants to simulate the call.
</p>
<p>
The way round this is to add extra methods to the mock when
generating it.
<pre>
<strong>Mock::generate('DatabaseConnection', 'MockDatabaseConnection', array('setOptions'));</strong>
</pre>
In a large test suite this could cause trouble, as you probably
already have a mock version of the class called
<span class="new_code">MockDatabaseConnection</span> without the extra methods.
The code generator will not generate a mock version of the class if
one of the same name already exists.
You will confusingly fail to see your method if another definition
was run first.
</p>
<p>
To cope with this, SimpleTest allows you to choose any name for the
new class at the same time as you add the extra methods.
<pre>
Mock::generate('DatabaseConnection', <strong>'MockDatabaseConnectionWithOptions'</strong>, array('setOptions'));
</pre>
Here the mock will behave as if the <span class="new_code">setOptions()</span>
existed in the original class.
</p>
<p>
Mock objects can only be used within test cases, as upon expectations
they send messages straight to the currently running test case.
Creating them outside a test case will cause a run time error
when an expectation is triggered and there is no running test case
for the message to end up.
We cover expectations next.
</p>
<h2>
<a class="target" name="expectations"></a>Mocks as critics</h2>
<p>
Although the server stubs approach insulates your tests from
real world disruption, it is only half the benefit.
You can have the class under test receiving the required
messages, but is your new class sending correct ones?
Testing this can get messy without a mock objects library.
</p>
<p>
By way of example, let's take a simple <span class="new_code">PageController</span>
class to handle a credit card payment form...
<pre>
class PaymentForm extends PageController {
function __construct($alert, $payment_gateway) { ... }
function makePayment($request) { ... }
}
</pre>
This class takes a <span class="new_code">PaymentGateway</span> to actually talk
to the bank.
It also takes an <span class="new_code">Alert</span> object to handle errors.
This class talks to the page or template.
It's responsible for painting the error message and highlighting any
form fields that are incorrect.
</p>
<p>
It might look something like...
<pre>
class Alert {
function warn($warning, $id) {
print '&lt;div class="warning"&gt;' . $warning . '&lt;/div&gt;';
print '&lt;style type="text/css"&gt;#' . $id . ' { background-color: red }&lt;/style&gt;';
}
}
</pre>
</p>
<p>
Our interest is in the <span class="new_code">makePayment()</span> method.
If we fail to enter a "CVV2" number (the three digit number
on the back of the credit card), we want to show an error rather than
try to process the payment.
In test form...
<pre>
&lt;?php
require_once('simpletest/autorun.php');
require_once('payment_form.php');
Mock::generate('Alert');
Mock::generate('PaymentGateway');
class PaymentFormFailuresShouldBeGraceful extends UnitTestCase {
function testMissingCvv2CausesAlert() {
$alert = new MockAlert();
<strong>$alert-&gt;expectOnce(
'warn',
array('Missing three digit security code', 'cvv2'));</strong>
$controller = new PaymentForm(<strong>$alert</strong>, new MockPaymentGateway());
$controller-&gt;makePayment($this-&gt;requestWithMissingCvv2());
}
function requestWithMissingCvv2() { ... }
}
?&gt;
</pre>
The first question you may be asking is, where are the assertions?
</p>
<p>
The call to <span class="new_code">expectOnce('warn', array(...))</span> instructs the mock
to expect a call to <span class="new_code">warn()</span> before the test ends.
When it gets a call to <span class="new_code">warn()</span>, it checks the arguments.
If the arguments don't match, then a failure is generated.
It also fails if the method is never called at all.
</p>
<p>
The test above not only asserts that <span class="new_code">warn</span> was called,
but that it received the string "Missing three digit security code"
and also the tag "cvv2".
The equivalent of <span class="new_code">assertIdentical()</span> is applied to both
fields when the parameters are compared.
</p>
<p>
If you are not interested in the actual message, and we are not
for user interface code that changes often, we can skip that
parameter with the "*" operator...
<pre>
class PaymentFormFailuresShouldBeGraceful extends UnitTestCase {
function testMissingCvv2CausesAlert() {
$alert = new MockAlert();
$alert-&gt;expectOnce('warn', array(<strong>'*'</strong>, 'cvv2'));
$controller = new PaymentForm($alert, new MockPaymentGateway());
$controller-&gt;makePayment($this-&gt;requestWithMissingCvv2());
}
function requestWithMissingCvv2() { ... }
}
</pre>
We can weaken the test further by missing
out the parameters array...
<pre>
function testMissingCvv2CausesAlert() {
$alert = new MockAlert();
<strong>$alert-&gt;expectOnce('warn');</strong>
$controller = new PaymentForm($alert, new MockPaymentGateway());
$controller-&gt;makePayment($this-&gt;requestWithMissingCvv2());
}
</pre>
This will only test that the method is called,
which is a bit drastic in this case.
Later on, we'll see how we can weaken the expectations more precisely.
</p>
<p>
Tests without assertions can be both compact and very expressive.
Because we intercept the call on the way into an object, here of
the <span class="new_code">Alert</span> class, we avoid having to assert its state
afterwards.
This not only avoids the assertions in the tests, but also having
to add extra test only accessors to the original code.
If you catch yourself adding such accessors, called "state based testing",
it's probably time to consider using mocks in the tests.
This is called "behaviour based testing", and is normally superior.
</p>
<p>
Let's add another test.
Let's make sure that we don't even attempt a payment without a CVV2...
<pre>
class PaymentFormFailuresShouldBeGraceful extends UnitTestCase {
function testMissingCvv2CausesAlert() { ... }
function testNoPaymentAttemptedWithMissingCvv2() {
$payment_gateway = new MockPaymentGateway();
<strong>$payment_gateway-&gt;expectNever('pay');</strong>
$controller = new PaymentForm(new MockAlert(), $payment_gateway);
$controller-&gt;makePayment($this-&gt;requestWithMissingCvv2());
}
...
}
</pre>
Asserting a negative can be very hard in tests, but
<span class="new_code">expectNever()</span> makes it easy.
</p>
<p>
<span class="new_code">expectOnce()</span> and <span class="new_code">expectNever()</span> are
sufficient for most tests, but
occasionally you want to test multiple events.
Normally for usability purposes we want all missing fields
in the form to light up, not just the first one.
This means that we should get multiple calls to
<span class="new_code">Alert::warn()</span>, not just one...
<pre>
function testAllRequiredFieldsHighlightedOnEmptyRequest() {
$alert = new MockAlert();<strong>
$alert-&gt;expectAt(0, 'warn', array('*', 'cc_number'));
$alert-&gt;expectAt(1, 'warn', array('*', 'expiry'));
$alert-&gt;expectAt(2, 'warn', array('*', 'cvv2'));
$alert-&gt;expectAt(3, 'warn', array('*', 'card_holder'));
$alert-&gt;expectAt(4, 'warn', array('*', 'address'));
$alert-&gt;expectAt(5, 'warn', array('*', 'postcode'));
$alert-&gt;expectAt(6, 'warn', array('*', 'country'));
$alert-&gt;expectCallCount('warn', 7);</strong>
$controller = new PaymentForm($alert, new MockPaymentGateway());
$controller-&gt;makePayment($this-&gt;requestWithMissingCvv2());
}
</pre>
The counter in <span class="new_code">expectAt()</span> is the number of times
the method has been called already.
Here we are asserting that every field will be highlighted.
</p>
<p>
Note that we are forced to assert the order too.
SimpleTest does not yet have a way to avoid this, but
this will be fixed in future versions.
</p>
<p>
Here is the full list of expectations you can set on a mock object
in <a href="http://simpletest.org/">SimpleTest</a>.
As with the assertions, these methods take an optional failure message.
<table>
<thead><tr>
<th>Expectation</th>
<th>Description</th>
</tr></thead>
<tbody>
<tr>
<td><span class="new_code">expect($method, $args)</span></td>
<td>Arguments must match if called</td>
</tr>
<tr>
<td><span class="new_code">expectAt($timing, $method, $args)</span></td>
<td>Arguments must match when called on the <span class="new_code">$timing</span>'th time</td>
</tr>
<tr>
<td><span class="new_code">expectCallCount($method, $count)</span></td>
<td>The method must be called exactly this many times</td>
</tr>
<tr>
<td><span class="new_code">expectMaximumCallCount($method, $count)</span></td>
<td>Call this method no more than <span class="new_code">$count</span> times</td>
</tr>
<tr>
<td><span class="new_code">expectMinimumCallCount($method, $count)</span></td>
<td>Must be called at least <span class="new_code">$count</span> times</td>
</tr>
<tr>
<td><span class="new_code">expectNever($method)</span></td>
<td>Must never be called</td>
</tr>
<tr>
<td><span class="new_code">expectOnce($method, $args)</span></td>
<td>Must be called once and with the expected arguments if supplied</td>
</tr>
<tr>
<td><span class="new_code">expectAtLeastOnce($method, $args)</span></td>
<td>Must be called at least once, and always with any expected arguments</td>
</tr>
</tbody>
</table>
Where the parameters are...
<dl>
<dt class="new_code">$method</dt>
<dd>The method name, as a string, to apply the condition to.</dd>
<dt class="new_code">$args</dt>
<dd>
The arguments as a list. Wildcards can be included in the same
manner as for <span class="new_code">setReturn()</span>.
This argument is optional for <span class="new_code">expectOnce()</span>
and <span class="new_code">expectAtLeastOnce()</span>.
</dd>
<dt class="new_code">$timing</dt>
<dd>
The only point in time to test the condition.
The first call starts at zero and the count is for
each method independently.
</dd>
<dt class="new_code">$count</dt>
<dd>The number of calls expected.</dd>
</dl>
</p>
<p>
If you have just one call in your test, make sure you're using
<span class="new_code">expectOnce</span>.<br>
Using <span class="new_code">$mocked-&gt;expectAt(0, 'method', 'args);</span>
on its own will allow the method to never be called.
Checking the arguments and the overall call count
are currently independant.
Add an <span class="new_code">expectCallCount()</span> expectation when you
are using <span class="new_code">expectAt()</span> unless zero calls is allowed.
</p>
<p>
Like the assertions within test cases, all of the expectations
can take a message override as an extra parameter.
Also the original failure message can be embedded in the output
as "%s".
</p>
</div>
References and related information...
<ul>
<li>
The original
<a href="http://www.mockobjects.com/">Mock objects</a> paper.
</li>
<li>
SimpleTest project page on <a href="http://sourceforge.net/projects/simpletest/">SourceForge</a>.
</li>
<li>
SimpleTest home page on <a href="http://www.lastcraft.com/simple_test.php">LastCraft</a>.
</li>
</ul>
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