357 lines
13 KiB
HTML
357 lines
13 KiB
HTML
<html>
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<META http-equiv="Content-Type" content="text/html; charset=UTF-8">
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Extending the SimpleTest unit tester with additional expectation classes
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</title>
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<link rel="stylesheet" type="text/css" href="docs.css" title="Styles">
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</head>
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<body>
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<div class="menu_back">
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<div class="menu">
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<h2>
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<a href="index.html">SimpleTest</a>
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</h2>
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<ul>
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<li>
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<a href="overview.html">Overview</a>
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</li>
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<li>
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<a href="unit_test_documentation.html">Unit tester</a>
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</li>
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<li>
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<a href="group_test_documentation.html">Group tests</a>
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</li>
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<li>
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<a href="server_stubs_documentation.html">Server stubs</a>
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</li>
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<li>
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<a href="mock_objects_documentation.html">Mock objects</a>
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</li>
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<li>
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<a href="partial_mocks_documentation.html">Partial mocks</a>
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</li>
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<li>
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<a href="reporter_documentation.html">Reporting</a>
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</li>
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<li>
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<span class="chosen">Expectations</span>
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</li>
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<li>
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<a href="web_tester_documentation.html">Web tester</a>
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<a href="form_testing_documentation.html">Testing forms</a>
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<li>
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<a href="authentication_documentation.html">Authentication</a>
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<li>
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<a href="browser_documentation.html">Scriptable browser</a>
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</li>
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</ul>
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</div>
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</div>
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<h1>Expectation documentation</h1>
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<div class="content">
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<p>
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<a class="target" name="mock">
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<h2>More control over mock objects</h2>
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</a>
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</p>
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<p>
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The default behaviour of the
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<a href="mock_objects_documentation.html">mock objects</a>
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in
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<a href="http://sourceforge.net/projects/simpletest/">SimpleTest</a>
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is either an identical match on the argument or to allow any argument at all.
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For almost all tests this is sufficient.
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Sometimes, though, you want to weaken a test case.
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</p>
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<p>
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One place where a test can be too tightly coupled is with
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text matching.
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Suppose we have a component that outputs a helpful error
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message when something goes wrong.
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You want to test that the correct error was sent, but the actual
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text may be rather long.
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If you test for the text exactly, then every time the exact wording
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of the message changes, you will have to go back and edit the test suite.
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</p>
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<p>
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For example, suppose we have a news service that has failed
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to connect to its remote source.
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<pre>
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<strong>class NewsService {
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...
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function publish(&$writer) {
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if (! $this->isConnected()) {
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$writer->write('Cannot connect to news service "' .
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$this->_name . '" at this time. ' .
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'Please try again later.');
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}
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...
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}
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}</strong>
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</pre>
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Here it is sending its content to a
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<span class="new_code">Writer</span> class.
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We could test this behaviour with a
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<span class="new_code">MockWriter</span> like so...
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<pre>
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class TestOfNewsService extends UnitTestCase {
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...
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function testConnectionFailure() {<strong>
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$writer = &new MockWriter($this);
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$writer->expectOnce('write', array(
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'Cannot connect to news service ' .
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'"BBC News" at this time. ' .
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'Please try again later.'));
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$service = &new NewsService('BBC News');
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$service->publish($writer);
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$writer->tally();</strong>
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}
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}
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</pre>
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This is a good example of a brittle test.
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If we decide to add additional instructions, such as
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suggesting an alternative news source, we will break
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our tests even though no underlying functionality
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has been altered.
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</p>
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<p>
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To get around this, we would like to do a regular expression
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test rather than an exact match.
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We can actually do this with...
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<pre>
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class TestOfNewsService extends UnitTestCase {
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...
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function testConnectionFailure() {
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$writer = &new MockWriter($this);<strong>
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$writer->expectOnce(
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'write',
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array(new WantedPatternExpectation('/cannot connect/i')));</strong>
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$service = &new NewsService('BBC News');
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$service->publish($writer);
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$writer->tally();
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}
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}
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</pre>
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Instead of passing in the expected parameter to the
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<span class="new_code">MockWriter</span> we pass an
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expectation class called
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<span class="new_code">WantedPatternExpectation</span>.
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The mock object is smart enough to recognise this as special
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and to treat it differently.
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Rather than simply comparing the incoming argument to this
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object, it uses the expectation object itself to
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perform the test.
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</p>
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<p>
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The <span class="new_code">WantedPatternExpectation</span> takes
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the regular expression to match in its constructor.
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Whenever a comparison is made by the <span class="new_code">MockWriter</span>
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against this expectation class, it will do a
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<span class="new_code">preg_match()</span> with this pattern.
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With our test case above, as long as "cannot connect"
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appears in the text of the string, the mock will issue a pass
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to the unit tester.
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The rest of the text does not matter.
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</p>
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<p>
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The possible expectation classes are...
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<table>
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<tbody>
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<tr>
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<td><span class="new_code">EqualExpectation</span></td><td>An equality, rather than the stronger identity comparison</td>
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</tr>
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<tr>
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<td><span class="new_code">NotEqualExpectation</span></td><td>An inequality comparison</td>
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</tr>
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<tr>
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<td><span class="new_code">IndenticalExpectation</span></td><td>The default mock object check which must match exactly</td>
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</tr>
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<tr>
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<td><span class="new_code">NotIndenticalExpectation</span></td><td>Inverts the mock object logic</td>
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</tr>
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<tr>
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<td><span class="new_code">WantedPatternExpectation</span></td><td>Uses a Perl Regex to match a string</td>
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</tr>
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<tr>
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<td><span class="new_code">NoUnwantedPatternExpectation</span></td><td>Passes only if failing a Perl Regex</td>
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</tr>
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<tr>
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<td><span class="new_code">IsAExpectation</span></td><td>Checks the type or class name only</td>
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</tr>
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<tr>
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<td><span class="new_code">NotAExpectation</span></td><td>Opposite of the <span class="new_code">IsAExpectation</span></td>
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</tr>
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<tr>
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<td><span class="new_code">MethodExistsExpectation</span></td><td>Checks a method is available on an object</td>
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</tr>
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</tbody>
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</table>
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Most take the expected value in the constructor.
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The exceptions are the pattern matchers, which take a regular expression,
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and the <span class="new_code">IsAExpectation</span> and <span class="new_code">NotAExpectation</span> which takes a type
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or class name as a string.
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</p>
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<p>
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<a class="target" name="behaviour">
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<h2>Using expectations to control stubs</h2>
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</a>
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</p>
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<p>
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The expectation classes can be used not just for sending assertions
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from mock objects, but also for selecting behaviour for either
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the
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<a href="mock_objects_documentation.html">mock objects</a>
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or the
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<a href="server_stubs_documentation.html">server stubs</a>.
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Anywhere a list of arguments is given, a list of expectation objects
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can be inserted instead.
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</p>
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<p>
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Suppose we want an authorisation server stub to simulate a successful login
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only if it receives a valid session object.
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We can do this as follows...
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<pre>
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Stub::generate('Authorisation');
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<strong>
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$authorisation = new StubAuthorisation();
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$authorisation->setReturnValue(
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'isAllowed',
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true,
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array(new IsAExpectation('Session', 'Must be a session')));
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$authorisation->setReturnValue('isAllowed', false);</strong>
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</pre>
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We have set the default stub behaviour to return false when
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<span class="new_code">isAllowed</span> is called.
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When we call the method with a single parameter that
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is a <span class="new_code">Session</span> object, it will return true.
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We have also added a second parameter as a message.
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This will be displayed as part of the mock object
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failure message if this expectation is the cause of
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a failure.
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</p>
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<p>
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This kind of sophistication is rarely useful, but is included for
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completeness.
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</p>
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<p>
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<a class="target" name="extending">
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<h2>Creating your own expectations</h2>
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</a>
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</p>
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<p>
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The expectation classes have a very simple structure.
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So simple that it is easy to create your own versions for
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commonly used test logic.
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</p>
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<p>
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As an example here is the creation of a class to test for
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valid IP addresses.
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In order to work correctly with the stubs and mocks the new
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expectation class should extend
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<span class="new_code">SimpleExpectation</span>...
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<pre>
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<strong>class ValidIp extends SimpleExpectation {
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function test($ip) {
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return (ip2long($ip) != -1);
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}
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function testMessage($ip) {
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return "Address [$ip] should be a valid IP address";
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}
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}</strong>
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</pre>
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There are only two methods to implement.
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The <span class="new_code">test()</span> method should
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evaluate to true if the expectation is to pass, and
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false otherwise.
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The <span class="new_code">testMessage()</span> method
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should simply return some helpful text explaining the test
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that was carried out.
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</p>
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<p>
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This class can now be used in place of the earlier expectation
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classes.
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</p>
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<p>
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<a class="target" name="unit">
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<h2>Under the bonnet of the unit tester</h2>
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</a>
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</p>
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<p>
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The <a href="http://sourceforge.net/projects/simpletest/">SimpleTest unit testing framework</a>
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also uses the expectation classes internally for the
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<a href="unit_test_documentation.html">UnitTestCase class</a>.
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We can also take advantage of these mechanisms to reuse our
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homebrew expectation classes within the test suites directly.
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</p>
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<p>
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The most crude way of doing this is to use the
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<span class="new_code">SimpleTest::assertExpectation()</span> method to
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test against it directly...
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<pre>
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<strong>class TestOfNetworking extends UnitTestCase {
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...
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function testGetValidIp() {
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$server = &new Server();
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$this->assertExpectation(
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new ValidIp(),
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$server->getIp(),
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'Server IP address->%s');
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}
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}</strong>
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</pre>
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This is a little untidy compared with our usual
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<span class="new_code">assert...()</span> syntax.
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</p>
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<p>
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For such a simple case we would normally create a
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separate assertion method on our test case rather
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than bother using the expectation class.
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If we pretend that our expectation is a little more
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complicated for a moment, so that we want to reuse it,
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we get...
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<pre>
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class TestOfNetworking extends UnitTestCase {
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...<strong>
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function assertValidIp($ip, $message = '%s') {
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$this->assertExpectation(new ValidIp(), $ip, $message);
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}</strong>
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function testGetValidIp() {
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$server = &new Server();<strong>
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$this->assertValidIp(
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$server->getIp(),
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'Server IP address->%s');</strong>
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}
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}
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</pre>
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It is unlikely we would ever need this degree of control
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over the testing machinery.
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It is rare to need the expectations for more than pattern
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matching.
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Also, complex expectation classes could make the tests
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harder to read and debug.
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These mechanisms are really of most use to authors of systems
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that will extend the test framework to create their own tool set.
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</p>
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</div>
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<div class="copyright">
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Copyright<br>Marcus Baker, Jason Sweat, Perrick Penet 2004
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</div>
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</body>
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</html>
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