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<h2>EasyMock 3.1 Readme</h2>
<p>Documentation for release 3.1 (2011-11-10)<br />
© 2001-2011 <a href="http://www.offis.de">OFFIS</a>, <a href="http://tammofreese.de">Tammo Freese</a>, <a href="http://www.ossia-conseil.com/blog/henri/">Henri Tremblay</a>.
</p>
<p>
EasyMock is a library that provides an easy way to use Mock Objects for given
interfaces or classes. EasyMock is available under the terms of the <a href="http://www.apache.org/licenses/LICENSE-2.0.txt">Apache 2 license</a>.
</p>
<p>
Mock Objects simulate parts of the behavior of domain code,
and are able to check whether they are used as defined.
Domain classes can be tested in isolation
by simulating their collaborators with Mock Objects.
</p>
<p>
Writing and maintaining Mock Objects often is a tedious
task that may introduce errors. EasyMock generates Mock Objects
dynamically - no need to write them, and no generated code!
</p>
<h2>
EasyMock Benefits
</h2>
<ul>
<li>Hand-writing classes for Mock Objects is not needed.
</li>
<li>Supports refactoring-safe Mock Objects: test code will not break at runtime when renaming methods or reordering method parameters
</li>
<li>Supports return values and exceptions.
</li>
<li>Supports checking the order of method calls, for one or more Mock Objects.
</li>
</ul>
<h2>
Requirements
</h2>
<ul>
<li>EasyMock only works with Java 1.5.0 and above.</li>
<li>cglib (2.2) and Objenesis (1.2) must be in the classpath to perform class mocking</li>
</ul>
<h2>
Installation
</h2>
<h3>Using Maven</h3>
EasyMock is available in the Maven central repository. Just add the following dependency to your pom.xml:
<pre>
<dependency>
<groupId>org.easymock</groupId>
<artifactId>easymock</artifactId>
<version>3.1</version>
<scope>test</scope>
</dependency>
</pre>
You can obviously use any other dependency tool compatible with the Maven repository.
<h3>Manually</h3>
<ul>
<li>Unzip the EasyMock zip file (<code>easymock-3.1.zip</code>).</li>
<li>Go into the <code>easymock-3.1</code> directory.</li>
<li>Add the EasyMock jar file (<code>easymock.jar</code>) to your classpath.</li>
<li>To perform class mocking, also add <a href="http://www.objenesis.org">Objenesis</a> and <a href="http://cglib.sourceforge.net/">Cglib</a> to your classpath.</li>
<li>The tests are in <code>easymock-3.1-tests.jar</code> and can be launched with a JUnit TestRunner
having JUnit 4.7 on top of EasyMock, cglib and Objenesis in your classpath.</li>
<li>The source code of EasyMock is stored in <code>easymock-3.1-sources.jar</code>.</li>
</ul>
<h2>
Usage
</h2>
<p>
Most parts of a software system do not work in isolation, but collaborate
with other parts to get their job done. In a lot of cases, we do not care
about using collaborators in unit testing, as we trust these collaborators.
If we <em>do</em> care about it, Mock Objects help us to test the unit under test
in isolation. Mock Objects replace collaborators of the unit under
test.
</p>
<p>
The following examples use the interface <code>Collaborator</code>:
</p>
<pre>
package org.easymock.samples;
public interface Collaborator {
void documentAdded(String title);
void documentChanged(String title);
void documentRemoved(String title);
byte voteForRemoval(String title);
byte[] voteForRemovals(String[] title);
}
</pre>
<p>
Implementors of this interface are collaborators
(in this case listeners) of a class named <code>ClassUnderTest</code>:
</p>
<pre>
public class ClassUnderTest {
// ...
public void addListener(Collaborator listener) {
// ...
}
public void addDocument(String title, byte[] document) {
// ...
}
public boolean removeDocument(String title) {
// ...
}
public boolean removeDocuments(String[] titles) {
// ...
}
}
</pre>
<p>
The code for both the class and the interface may be found
in the package <code>org.easymock.samples</code> in <code>easymock-3.1-samples.jar</code>
from the EasyMock zip delivery.
</p>
<p>
The following examples assume that you are familiar with the JUnit testing framework.
Although the tests shown here use JUnit 4, you may as well use JUnit 3 or TestNG.
</p>
<h3>
The first Mock Object
</h3>
<p>
We will now build a test case and toy around with it to understand the
functionality of the EasyMock package. <code>easymock-3.1-samples.jar</code>
contains a modified version of this test. Our first test should check
whether the removal of a non-existing document does <strong>not </strong> lead to a notification
of the collaborator. Here is the test without the definition of the
Mock Object:
</p>
<pre>
package org.easymock.samples;
import org.junit.*;
public class ExampleTest {
private ClassUnderTest classUnderTest;
private Collaborator mock;
@Before
public void setUp() {
classUnderTest = new ClassUnderTest();
classUnderTest.addListener(mock);
}
@Test
public void testRemoveNonExistingDocument() {
// This call should not lead to any notification
// of the Mock Object:
classUnderTest.removeDocument("Does not exist");
}
}
</pre>
<p>
For many tests using EasyMock,
we only need a static import of methods of <code>org.easymock.EasyMock</code>.
</p>
<pre>
import static org.easymock.EasyMock.*;
import org.junit.*;
public class ExampleTest {
private ClassUnderTest classUnderTest;
private Collaborator mock;
}
</pre>
<p>
To get a Mock Object, we need to
</p>
<ol>
<li>create a Mock Object for the interface we would like to simulate,
</li>
<li>record the expected behavior, and
</li>
<li>switch the Mock Object to replay state.
</li>
</ol>
<p>
Here is a first example:
</p>
<pre>
@Before
public void setUp() {
mock = createMock(Collaborator.class); // 1
classUnderTest = new ClassUnderTest();
classUnderTest.addListener(mock);
}
@Test
public void testRemoveNonExistingDocument() {
// 2 (we do not expect anything)
replay(mock); // 3
classUnderTest.removeDocument("Does not exist");
}
</pre>
<p>
After activation in step 3, <code>mock</code>
is a Mock Object for the <code>Collaborator</code>
interface that expects no calls. This means that if we change
our <code>ClassUnderTest</code> to call
any of the interface's methods, the Mock Object will throw
an <code>AssertionError</code>:
</p>
<pre>
java.lang.AssertionError:
Unexpected method call documentRemoved("Does not exist"):
at org.easymock.internal.MockInvocationHandler.invoke(MockInvocationHandler.java:29)
at org.easymock.internal.ObjectMethodsFilter.invoke(ObjectMethodsFilter.java:44)
at $Proxy0.documentRemoved(Unknown Source)
at org.easymock.samples.ClassUnderTest.notifyListenersDocumentRemoved(ClassUnderTest.java:74)
at org.easymock.samples.ClassUnderTest.removeDocument(ClassUnderTest.java:33)
at org.easymock.samples.ExampleTest.testRemoveNonExistingDocument(ExampleTest.java:24)
...
</pre>
<h3>
Adding Behavior
</h3>
<p>
Let us write a second test. If a document
is added on the class under test, we expect a call to <code>mock.documentAdded()</code>
on the Mock Object with the title of the document as argument:
</p>
<pre>
@Test
public void testAddDocument() {
mock.documentAdded("New Document"); // 2
replay(mock); // 3
classUnderTest.addDocument("New Document", new byte[0]);
}
</pre>
<p>
So in the record state (before calling <code>replay</code>),
the Mock Object does <em>not</em> behave like a Mock Object,
but it records method calls. After calling <code>replay</code>,
it behaves like a Mock Object, checking whether the expected
method calls are really done.
</p>
<p>
If <code>classUnderTest.addDocument("New Document", new byte[0])</code>
calls the expected method with a wrong argument, the Mock Object will complain
with an <code>AssertionError</code>:
</p>
<pre>
java.lang.AssertionError:
Unexpected method call documentAdded("Wrong title"):
documentAdded("New Document"): expected: 1, actual: 0
at org.easymock.internal.MockInvocationHandler.invoke(MockInvocationHandler.java:29)
at org.easymock.internal.ObjectMethodsFilter.invoke(ObjectMethodsFilter.java:44)
at $Proxy0.documentAdded(Unknown Source)
at org.easymock.samples.ClassUnderTest.notifyListenersDocumentAdded(ClassUnderTest.java:61)
at org.easymock.samples.ClassUnderTest.addDocument(ClassUnderTest.java:28)
at org.easymock.samples.ExampleTest.testAddDocument(ExampleTest.java:30)
...
</pre>
<p>
All missed expectations are shown, as well as all fulfilled
expectations for the unexpected call (none in this case). If the method
call is executed too often, the Mock Object complains, too:
</p>
<pre>
java.lang.AssertionError:
Unexpected method call documentAdded("New Document"):
documentAdded("New Document"): expected: 1, actual: 2
at org.easymock.internal.MockInvocationHandler.invoke(MockInvocationHandler.java:29)
at org.easymock.internal.ObjectMethodsFilter.invoke(ObjectMethodsFilter.java:44)
at $Proxy0.documentAdded(Unknown Source)
at org.easymock.samples.ClassUnderTest.notifyListenersDocumentAdded(ClassUnderTest.java:62)
at org.easymock.samples.ClassUnderTest.addDocument(ClassUnderTest.java:29)
at org.easymock.samples.ExampleTest.testAddDocument(ExampleTest.java:30)
...
</pre>
<h3>
Verifying Behavior
</h3>
<p>
There is one error that we have not handled so far: If we specify
behavior, we would like to verify that it is actually used. The current
test would pass if no method on the Mock Object is called. To verify that the
specified behavior has been used, we have to call
<code>verify(mock)</code>:
</p>
<pre>
@Test
public void testAddDocument() {
mock.documentAdded("New Document"); // 2
replay(mock); // 3
classUnderTest.addDocument("New Document", new byte[0]);
verify(mock);
}
</pre>
<p>
If the method is not called on the Mock Object, we now get the
following exception:
</p>
<pre>
java.lang.AssertionError:
Expectation failure on verify:
documentAdded("New Document"): expected: 1, actual: 0
at org.easymock.internal.MocksControl.verify(MocksControl.java:70)
at org.easymock.EasyMock.verify(EasyMock.java:536)
at org.easymock.samples.ExampleTest.testAddDocument(ExampleTest.java:31)
...
</pre>
<p>
The message of the exception lists all missed expectations.
</p>
<h3>
Expecting an Explicit Number of Calls
</h3>
<p>
Up to now, our test has only considered a single method call. The next
test should check whether the addition of an already existing
document leads to a call to <code>mock.documentChanged()</code>
with the appropriate argument. To be sure, we check this three
times (hey, it is an example ;-)):
</p>
<pre>
@Test
public void testAddAndChangeDocument() {
mock.documentAdded("Document");
mock.documentChanged("Document");
mock.documentChanged("Document");
mock.documentChanged("Document");
replay(mock);
classUnderTest.addDocument("Document", new byte[0]);
classUnderTest.addDocument("Document", new byte[0]);
classUnderTest.addDocument("Document", new byte[0]);
classUnderTest.addDocument("Document", new byte[0]);
verify(mock);
}
</pre>
<p>
To avoid the repetition of <code>mock.documentChanged("Document")</code>,
EasyMock provides a shortcut. We may specify the call count with the method
<code>times(int times)</code> on the object returned by
<code>expectLastCall()</code>. The code then looks like:
</p>
<pre>
@Test
public void testAddAndChangeDocument() {
mock.documentAdded("Document");
mock.documentChanged("Document");
expectLastCall().times(3);
replay(mock);
classUnderTest.addDocument("Document", new byte[0]);
classUnderTest.addDocument("Document", new byte[0]);
classUnderTest.addDocument("Document", new byte[0]);
classUnderTest.addDocument("Document", new byte[0]);
verify(mock);
}
</pre>
<p>
If the method is called too often, we get an exception that
tells us that the method has been called too many times.
The failure occurs immediately at the first method call
exceeding the limit:
</p>
<pre>
java.lang.AssertionError:
Unexpected method call documentChanged("Document"):
documentChanged("Document"): expected: 3, actual: 4
at org.easymock.internal.MockInvocationHandler.invoke(MockInvocationHandler.java:29)
at org.easymock.internal.ObjectMethodsFilter.invoke(ObjectMethodsFilter.java:44)
at $Proxy0.documentChanged(Unknown Source)
at org.easymock.samples.ClassUnderTest.notifyListenersDocumentChanged(ClassUnderTest.java:67)
at org.easymock.samples.ClassUnderTest.addDocument(ClassUnderTest.java:26)
at org.easymock.samples.ExampleTest.testAddAndChangeDocument(ExampleTest.java:43)
...
</pre>
<p>
If there are too few calls, <code>verify(mock)</code>
throws an <code>AssertionError</code>:
</p>
<pre>
java.lang.AssertionError:
Expectation failure on verify:
documentChanged("Document"): expected: 3, actual: 2
at org.easymock.internal.MocksControl.verify(MocksControl.java:70)
at org.easymock.EasyMock.verify(EasyMock.java:536)
at org.easymock.samples.ExampleTest.testAddAndChangeDocument(ExampleTest.java:43)
...
</pre>
<h3>
Specifying Return Values
</h3>
<p>
For specifying return values,
we wrap the expected call in <code>expect(T value)</code> and specify the return value
with the method <code>andReturn(Object returnValue)</code> on the object returned by
<code>expect(T value)</code>.
</p>
<p>
As an example, we check the workflow for document
removal. If <code>ClassUnderTest</code> gets a call for document
removal, it asks all collaborators for their vote for removal
with calls to <code>byte voteForRemoval(String title)</code> value.
Positive return values are a vote for
removal. If the sum of all values is positive, the document is removed
and <code>documentRemoved(String title)</code> is called on
all collaborators:
</p>
<pre>
@Test
public void testVoteForRemoval() {
mock.documentAdded("Document"); // expect document addition
// expect to be asked to vote for document removal, and vote for it
expect(mock.voteForRemoval("Document")).andReturn((byte) 42);
mock.documentRemoved("Document"); // expect document removal
replay(mock);
classUnderTest.addDocument("Document", new byte[0]);
assertTrue(classUnderTest.removeDocument("Document"));
verify(mock);
}
@Test
public void testVoteAgainstRemoval() {
mock.documentAdded("Document"); // expect document addition
// expect to be asked to vote for document removal, and vote against it
expect(mock.voteForRemoval("Document")).andReturn((byte) -42);
replay(mock);
classUnderTest.addDocument("Document", new byte[0]);
assertFalse(classUnderTest.removeDocument("Document"));
verify(mock);
}
</pre>
<p>
The type of the returned value is checked at compile time. As an example,
the following code will not compile, as the type of the provided return value
does not match the method's return value:
</p>
<pre>
expect(mock.voteForRemoval("Document")).andReturn("wrong type");
</pre>
<p>
Instead of calling <code>expect(T value)</code>
to retrieve the object for setting the return value,
we may also use the object returned by <code>expectLastCall()</code>.
Instead of
</p>
<pre>
expect(mock.voteForRemoval("Document")).andReturn((byte) 42);
</pre>
<p>
we may use
</p>
<pre>
mock.voteForRemoval("Document");
expectLastCall().andReturn((byte) 42);
</pre>
<p>
This type of specification should only be used if the line gets too long,
as it does not support type checking at compile time.
</p>
<h3>
Working with Exceptions
</h3>
<p>
For specifying exceptions (more exactly: Throwables) to be thrown, the object returned by
<code>expectLastCall()</code> and <code>expect(T value)</code> provides the method
<code>andThrow(Throwable throwable)</code>.
The method has to be called in record state after the call to the Mock Object for
which it specifies the <code>Throwable</code> to be thrown.
</p>
<p>
Unchecked exceptions (that is, <code>RuntimeException</code>, <code>Error</code>
and all their subclasses) can be thrown from every method. Checked exceptions can only be
thrown from the methods that do actually throw them.
</p>
<h3>
Creating Return Values or Exceptions
</h3>
<p>
Sometimes we would like our mock object to return a value or throw an exception
that is created at the time of the actual call. Since EasyMock 2.2, the object returned by
<code>expectLastCall()</code> and <code>expect(T value)</code> provides the method
<code>andAnswer(IAnswer answer)</code> which allows to specify an implementation of the
interface <code>IAnswer</code> that is used to create the return value or exception.
</p>
<p>
Inside an <code>IAnswer</code> callback, the arguments passed to the mock call
are available via <code>EasyMock.getCurrentArguments()</code>.
If you use these, refactorings like reordering parameters may break your tests.
You have been warned.
</p>
<p>
An alternative to <code>IAnswer</code> are the <code>andDelegateTo</code> and
<code>andStubDelegateTo</code> methods. They allow to delegate the call to a
concrete implementation of the mocked interface that will then provide the answer.
The pros are that the arguments found in <code>EasyMock.getCurrentArguments()</code>
for <code>IAnswer</code> are now passed to the method of the concrete implementation.
This is refactoring safe. The cons are that you have to provide an implementation
which is kind of doing a mock manually... Which is what you try to avoid by
using EasyMock. It can also be painful if the interface has many methods. Finally,
the type of the concrete class can't be checked statically against the mock type.
If for some reason, the concrete class isn't implementing the method that is
delegated, you will get an exception during the replay only. However, this
case should be quite rare.
</p>
<p>
To understand correctly the two options, here is an example:
</p>
<pre>
List<String> l = createMock(List.class);
// andAnswer style
expect(l.remove(10)).andAnswer(new IAnswer<String>() {
public String answer() throws Throwable {
return getCurrentArguments()[0].toString();
}
});
// andDelegateTo style
expect(l.remove(10)).andDelegateTo(new ArrayList<String>() {
@Override
public String remove(int index) {
return Integer.toString(index);
}
});
</pre>
<h3>
Changing Behavior for the Same Method Call
</h3>
<p>
It is also possible to specify a changing behavior for a method.
The methods <code>times</code>, <code>andReturn</code>, and <code>andThrow</code>
may be chained. As an example, we define <code>voteForRemoval("Document")</code> to
</p>
<ul>
<li>return 42 for the first three calls,
</li>
<li>throw a <code>RuntimeException</code> for the next four calls,
</li>
<li>return -42 once.
</li>
</ul>
<pre>
expect(mock.voteForRemoval("Document"))
.andReturn((byte) 42).times(3)
.andThrow(new RuntimeException(), 4)
.andReturn((byte) -42);
</pre>
<h3>
Relaxing Call Counts
</h3>
<p>
To relax the expected call counts, there are additional methods
that may be used instead of <code>times(int count)</code>:
</p>
<dl>
<dt><code>times(int min, int max)</code></dt>
<dd>to expect between <code>min</code> and <code>max</code> calls,</dd>
<dt><code>atLeastOnce()</code></dt>
<dd>to expect at least one call, and</dd>
<dt><code>anyTimes()</code></dt>
<dd>to expected an unrestricted number of calls.</dd>
</dl>
<p>
If no call count is specified, one call is expected. If we would like to state this
explicitely, <code>once()</code> or <code>times(1)</code> may be used.
</p>
<h3>
Strict Mocks
</h3>
<p>
On a Mock Object returned by a <code>EasyMock.createMock()</code>,
the order of method calls is not checked.
If you would like a strict Mock Object that checks the order of method calls,
use <code>EasyMock.create<i>Strict</i>Mock()</code> to create it.</p>
<p>
If an unexpected method is called on a strict Mock Object,
the message of the exception will show the method calls
expected at this point followed by the first conflicting one.
<code>verify(mock)</code> shows all missing method calls.
</p>
<h3>
Switching Order Checking On and Off
</h3>
<p>
Sometimes, it is necessary to have a Mock Object that checks the order of only some calls.
In record phase, you may switch order checking on by calling <code>checkOrder(mock, true)</code>
and switch it off by calling <code>checkOrder(mock, false)</code>.
</p>
<p>
There are two differences between a strict Mock Object and a normal Mock Object:
</p>
<ol>
<li> A strict Mock Object has order checking enabled after creation. </li>
<li> A strict Mock Object has order checking enabled after reset (see <em>Reusing a Mock Object</em>). </li>
</ol>
<h3>
Flexible Expectations with Argument Matchers
</h3>
<p>
To match an actual method call on the Mock Object with an
expectation, <code>Object</code> arguments are by default compared with
<code>equals()</code>. This may lead to problems. As an example,
we consider the following expectation:
</p>
<pre>
String[] documents = new String[] { "Document 1", "Document 2" };
expect(mock.voteForRemovals(documents)).andReturn(42);
</pre>
<p>
If the method is called with another array with the same contents,
we get an exception, as <code>equals()</code> compares object
identity for arrays:
</p>
<pre>
java.lang.AssertionError:
Unexpected method call voteForRemovals([Ljava.lang.String;@9a029e):
voteForRemovals([Ljava.lang.String;@2db19d): expected: 1, actual: 0
documentRemoved("Document 1"): expected: 1, actual: 0
documentRemoved("Document 2"): expected: 1, actual: 0
at org.easymock.internal.MockInvocationHandler.invoke(MockInvocationHandler.java:29)
at org.easymock.internal.ObjectMethodsFilter.invoke(ObjectMethodsFilter.java:44)
at $Proxy0.voteForRemovals(Unknown Source)
at org.easymock.samples.ClassUnderTest.listenersAllowRemovals(ClassUnderTest.java:88)
at org.easymock.samples.ClassUnderTest.removeDocuments(ClassUnderTest.java:48)
at org.easymock.samples.ExampleTest.testVoteForRemovals(ExampleTest.java:83)
...
</pre>
<p>
To specify that only array equality is needed for this call, we may use the method
<code>aryEq</code> that is statically imported from the <code>EasyMock</code> class:
</p>
<pre>
String[] documents = new String[] { "Document 1", "Document 2" };
expect(mock.voteForRemovals(aryEq(documents))).andReturn(42);
</pre>
<p>
If you would like to use matchers in a call, you have to specify matchers for all
arguments of the method call.
</p>
<p>
There are a couple of predefined argument matchers available.
</p>
<dl>
<dt><code>eq(X value)</code></dt>
<dd>Matches if the actual value is equals the expected value. Available for all primitive types and for objects.</dd>
<dt><code>anyBoolean()</code>, <code>anyByte()</code>, <code>anyChar()</code>, <code>anyDouble()</code>, <code>anyFloat()</code>, <code>anyInt()</code>, <code>anyLong()</code>, <code>anyObject()</code>, <code>anyObject(Class clazz)</code>, <code>anyShort()</code></dt>
<dd>Matches any value. Available for all primitive types and for objects.</dd>
<dt><code>eq(X value, X delta)</code></dt>
<dd>Matches if the actual value is equal to the given value allowing the given delta. Available for <code>float</code> and <code>double</code>.</dd>
<dt><code>aryEq(X value)</code></dt>
<dd>Matches if the actual value is equal to the given value according to <code>Arrays.equals()</code>. Available for primitive and object arrays.</dd>
<dt><code>isNull()</code>, <code>isNull(Class clazz)</code></dt>
<dd>Matches if the actual value is null. Available for objects.</dd>
<dt><code>notNull()</code>, <code>notNull(Class clazz)</code></dt>
<dd>Matches if the actual value is not null. Available for objects.</dd>
<dt><code>same(X value)</code></dt>
<dd>Matches if the actual value is the same as the given value. Available for objects.</dd>
<dt><code>isA(Class clazz)</code></dt>
<dd>Matches if the actual value is an instance of the given class, or if it is in instance of a class that extends or implements the given class. Null always return false. Available for objects.</dd>
<dt><code>lt(X value)</code>, <code>leq(X value)</code>, <code>geq(X value)</code>, <code>gt(X value)</code></dt>
<dd>Matches if the actual value is less/less or equal/greater or equal/greater than the given value. Available for all numeric primitive types and <code>Comparable</code>.</dd>
<dt><code>startsWith(String prefix), contains(String substring), endsWith(String suffix)</code></dt>
<dd>Matches if the actual value starts with/contains/ends with the given value. Available for <code>String</code>s.</dd>
<dt><code>matches(String regex), find(String regex)</code></dt>
<dd>Matches if the actual value/a substring of the actual value matches the given regular expression. Available for <code>String</code>s.</dd>
<dt><code>and(X first, X second)</code></dt>
<dd>Matches if the matchers used in <code>first</code> and <code>second</code> both match. Available for all primitive types and for objects.</dd>
<dt><code>or(X first, X second)</code></dt>
<dd>Matches if one of the matchers used in <code>first</code> and <code>second</code> match. Available for all primitive types and for objects.</dd>
<dt><code>not(X value)</code></dt>
<dd>Matches if the matcher used in <code>value</code> does not match.</dd>
<dt><code>cmpEq(X value)</code></dt>
<dd>Matches if the actual value is equals according to <code>Comparable.compareTo(X o)</code>. Available for all numeric primitive types and <code>Comparable</code>.</dd>
<dt><code>cmp(X value, Comparator<X> comparator, LogicalOperator operator)</code></dt>
<dd>Matches if <code>comparator.compare(actual, value) operator 0</code> where the operator is <,<=,>,>= or ==. Available for objects.</dd>
<dt><code>capture(Capture<T> capture)</code>, <code>captureXXX(Capture<T> capture)</code></dt>
<dd>Matches any value but captures it in the <code>Capture</code> parameter for later access. You can do <code>and(someMatcher(...), capture(c))</code> to
capture a parameter from a specific call to the method. You can also specify a <code>CaptureType</code> telling that a given <code>Capture</code> should keep
the first, the last, all or no captured values.</dd>
</dl>
<h3>
Defining your own Argument Matchers
</h3>
<p>
Sometimes it is desirable to define own argument matchers. Let's say that an
argument matcher is needed that matches an exception if the given exception has the same type and an equal message.
It should be used this way:
</p>
<pre>
IllegalStateException e = new IllegalStateException("Operation not allowed.")
expect(mock.logThrowable(eqException(e))).andReturn(true);
</pre>
<p>
Two steps are necessary to achieve this: The new argument matcher has to be defined,
and the static method <code>eqException</code> has to be declared.
</p>
<p>
To define the new argument matcher, we implement the interface <code>org.easymock.IArgumentMatcher</code>.
This interface contains two methods: <code>matches(Object actual)</code> checks whether the actual argument
matches the given argument, and <code>appendTo(StringBuffer buffer)</code> appends a string representation
of the argument matcher to the given string buffer. The implementation is straightforward:
</p>
<pre>
import org.easymock.IArgumentMatcher;
public class ThrowableEquals implements IArgumentMatcher {
private Throwable expected;
public ThrowableEquals(Throwable expected) {
this.expected = expected;
}
public boolean matches(Object actual) {
if (!(actual instanceof Throwable)) {
return false;
}
String actualMessage = ((Throwable) actual).getMessage();
return expected.getClass().equals(actual.getClass())
&& expected.getMessage().equals(actualMessage);
}
public void appendTo(StringBuffer buffer) {
buffer.append("eqException(");
buffer.append(expected.getClass().getName());
buffer.append(" with message \"");
buffer.append(expected.getMessage());
buffer.append("\"")");
}
}
</pre>
<p>
The method <code>eqException</code> must create the argument matcher with the given Throwable,
report it to EasyMock via the static method <code>reportMatcher(IArgumentMatcher matcher)</code>,
and return a value so that it may be used inside the call
(typically <code>0</code>, <code>null</code> or <code>false</code>). A first attempt may look like:
</p>
<pre>
public static Throwable eqException(Throwable in) {
EasyMock.reportMatcher(new ThrowableEquals(in));
return null;
}
</pre>
<p>
However, this only works if the method <code>logThrowable</code> in the example usage accepts
<code>Throwable</code>s, and does not require something more specific like a <code>RuntimeException</code>.
In the latter case, our code sample would not compile:
</p>
<pre>
IllegalStateException e = new IllegalStateException("Operation not allowed.")
expect(mock.logThrowable(eqException(e))).andReturn(true);
</pre>
<p>
Java 5.0 to the rescue: Instead of defining <code>eqException</code> with a <code>Throwable</code> as
parameter and return value, we use a generic type that extends <code>Throwable</code>:
</p>
<pre>
public static <T extends Throwable> T eqException(T in) {
reportMatcher(new ThrowableEquals(in));
return null;
}
</pre>
<h3>
Reusing a Mock Object
</h3>
<p>
Mock Objects may be reset by <code>reset(mock)</code>.
</p>
<p>
If needed, a mock can also be converted from one type to another by calling <code>resetToNice(mock)</code>,
<code>resetToDefault(mock)</code> ou <code>resetToStrict(mock)</code>.
</p>
<h3>
Using Stub Behavior for Methods
</h3>
<p>
Sometimes, we would like our Mock Object to respond to some method calls, but we do not want to
check how often they are called, when they are called, or even if they are called at all.
This stub behavoir may be defined by using the methods <code>andStubReturn(Object value)</code>,
<code>andStubThrow(Throwable throwable)</code>, <code>andStubAnswer(IAnswer<Tgt; answer)</code>
and <code>asStub()</code>. The following code
configures the MockObject to answer 42 to <code>voteForRemoval("Document")</code> once
and -1 for all other arguments:
</p>
<pre>
expect(mock.voteForRemoval("Document")).andReturn(42);
expect(mock.voteForRemoval(not(eq("Document")))).andStubReturn(-1);
</pre>
<h3>
Nice Mocks
</h3>
<p>
On a Mock Object returned by <code>createMock()</code> the default behavior for all methods is to throw an
<code>AssertionError</code> for all unexpected method calls.
If you would like a "nice" Mock Object that by default allows all method calls and returns
appropriate empty values (<code>0</code>, <code>null</code> or <code>false</code>), use <code>create<i>Nice</i>Mock()</code> instead.
</p>
<a id="Object_Methods"/><h3>Object Methods</h3>
<p>
The behavior for the four Object methods <code>equals()</code>,
<code>hashCode()</code>, <code>toString()</code> and <code>finalize()</code>
cannot be changed for Mock Objects created with EasyMock,
even if they are part of the interface for which the
Mock Object is created.
</p>
<h3>Checking Method Call Order Between Mocks</h3>
<p>
Up to this point, we have seen a mock object as a single object that is configured by static methods
on the class <code>EasyMock</code>. But many of these static methods just identify the hidden control of the Mock Object
and delegate to it. A Mock Control is an object implementing the <code>IMocksControl</code> interface.
</p>
<p>
So instead of
</p>
<pre>
IMyInterface mock = createStrictMock(IMyInterface.class);
replay(mock);
verify(mock);
reset(mock);
</pre>
<p>
we may use the equivalent code:
</p>
<pre>
IMocksControl ctrl = createStrictControl();
IMyInterface mock = ctrl.createMock(IMyInterface.class);
ctrl.replay();
ctrl.verify();
ctrl.reset();
</pre>
<p>
The IMocksControl allows to create more than one Mock Object, and so it is possible to check the order of method calls
between mocks. As an example, we set up two mock objects for the interface <code>IMyInterface</code>, and we expect the calls
<code>mock1.a()</code> and <code>mock2.a()</code> ordered, then an open number of calls to <code>mock1.c()</code>
and <code>mock2.c()</code>, and finally <code>mock2.b()</code> and <code>mock1.b()</code>, in this order:
</p>
<pre>
IMocksControl ctrl = createStrictControl();
IMyInterface mock1 = ctrl.createMock(IMyInterface.class);
IMyInterface mock2 = ctrl.createMock(IMyInterface.class);
mock1.a();
mock2.a();
ctrl.checkOrder(false);
mock1.c();
expectLastCall().anyTimes();
mock2.c();
expectLastCall().anyTimes();
ctrl.checkOrder(true);
mock2.b();
mock1.b();
ctrl.replay();
</pre>
<h3>Naming Mock Objects</h3>
<p>
Mock Objects can be named at creation using
<code>createMock(String name, Class<T> toMock)</code>,
<code>createStrictMock(String name, Class<T> toMock)</code> or
<code>createNiceMock(String name, Class<T> toMock)</code>.
The names will be shown in exception failures.
</p>
<h3>Serializing Mocks</h3>
<p>
Mocks can be serialized at any time during their life. However, there are some obvious contraints:
</p>
<ul>
<li>All used matchers should be serializable (all genuine EasyMock ones are)
</li>
<li>Recorded parameters should also be serializable
</li>
</ul>
<h3>Multithreading</h3>
<p>
During recording, a mock is <b>not</b> thread-safe. So a giving mock (or mocks linked to the same <code>IMocksControl</code>)
can only be recorded from a single thread. However, different mocks can be recorded simultaneously in different threads.
</p>
<p>
During the replay phase, mocks are by default thread-safe. This can be change for a given mock if <code>makeThreadSafe(mock, false)</code>
is called during the recording phase. This can prevent deadlocks in some rare situations.
</p>
<p>
Finally, calling <code>checkIsUsedInOneThread(mock, true)</code> on a mock will make sure the mock is used in only one thread and
throw an exception otherwise. This can be handy to make sure a thread-unsafe mocked object is used correctly.
</p>
<h3>EasyMockSupport</h3>
<p>
<code>EasyMockSupport</code> is a class that meant to be used as a helper or base class to your test cases. It will automatically registers all
created mocks (or in fact all created controls) and to replay, reset or verify them in batch instead of explicitly. Here's a JUnit example:
</p>
<pre>
public class SupportTest extends EasyMockSupport {
private Collaborator firstCollaborator;
private Collaborator secondCollaborator;
private ClassTested classUnderTest;
@Before
public void setup() {
classUnderTest = new ClassTested();
}
@Test
public void addDocument() {
// creation phase
firstCollaborator = createMock(Collaborator.class);
secondCollaborator = createMock(Collaborator.class);
classUnderTest.addListener(firstCollaborator);
classUnderTest.addListener(secondCollaborator);
// recording phase
firstCollaborator.documentAdded("New Document");
secondCollaborator.documentAdded("New Document");
replayAll(); // replay all mocks at once
// test
classUnderTest.addDocument("New Document", new byte[0]);
verifyAll(); // verify all mocks at once
}
}
</pre>
<h3>Altering EasyMock default behavior</h3>
<p>
EasyMock provides a property mecanisim allowing to alter its behavior. It mainly aims
at allowing to use a legacy behavior on a new version. Currently supported properties are:
</p>
<dl>
<dt><code>easymock.notThreadSafeByDefault</code></dt>
<dd>If true, a mock won't be thread-safe by default. Possible values are "true" or "false". Default is false</dd>
<dt><code>easymock.enableThreadSafetyCheckByDefault</code></dt>
<dd>If true, thread-safety check feature will be on by default. Possible values are "true" or "false". Default is false</dd>
<dt><code>easymock.disableClassMocking</code></dt>
<dd>Do not allow class mocking (only allow interface mocking). Possible values are "true" or "false". Default is false.</dd>
</dl>
<p>
Properties can be set in three ways. Each step in the list can overwrite
previous ones.
</p>
<ul>
<li>In an <code>easymock.properties</code> file set in the classpath default package
</li>
<li>As a system property
</li>
<li>By calling <code>EasyMock.setEasyMockProperty</code>. Constants are available
in the <code>EasyMock</code> class
</li>
</ul>
<h3>Backward Compatibility</h3>
<p>EasyMock 3 still has a Class Extension project (although deprecated) to
allow an easier migration from EasyMock 2 to EasyMock 3. It is a source not a binary
compatibility. So the code will need to be recompiled.
</p>
<p>EasyMock 2.1 introduced a callback feature that has been removed in EasyMock 2.2,
as it was too complex. Since EasyMock 2.2, the <code>IAnswer</code> interface
provides the functionality for callbacks.
</p>
<h3>OSGi</h3>
<p>
EasyMock jar can be used as an OSGi bundle. It exports <code>org.easymock</code>,
<code>org.easymock.internal</code> and <code>org.easymock.internal.matchers</code>
packages. However, to import the two latter, you need to specify the <code>poweruser</code>
attribute at true (<code>poweruser=true</code>). These packages are meant to be
used to extend EasyMock so they usually don't need to be imported.
</p>
<h3>Partial mocking</h3>
<p>
Sometimes you may need to mock only some methods of a class and keep
the normal behavior of others. This usually happens when you want to
test a method that calls some others in the same class. So you want to
keep the normal behavior of the tested method and mock the others.
</p>
<p>
In this case, the first thing to do is to consider a refactoring since
most of the time this problem caused by a bad design. If it's not
the case or if you can't do otherwise because of some development constraints,
here's the solution.
</p>
<pre>
ToMock mock = createMockBuilder(ToMock.class)
.addMockedMethod("mockedMethod").createMock();
</pre>
<p>In this case only the methods added with <code>addMockedMethod(s)</code> will be
mocked (<code>mockedMethod()</code> in the example). The others will still
behave as they used to. One exception: abstract methods are conveniently mocked by default.
</p>
<p><code>createMockBuilder</code> returns a <code>IMockBuilder</code> interface. It contains various methods to
easily create a partial mock. Have a look at the javadoc.
</p>
<p>
<b>Remark:</b> EasyMock provides a default behavior for Object's methods (<i>equals, hashCode, toString, finalize</i>).
However, for a partial mock, if these methods are not mocked explicitly, they will have their normal behavior
instead of EasyMock default's one.
</p>
<h3>Self testing</h3>
<p>
It is possible to create a mock by calling one of its constructor. This can be handy when a
class method needs to be tested but the class other methods, mocked. For that you should do
something like
</p>
<pre>
ToMock mock = createMockBuilder(ToMock.class)
.withConstructor(1, 2, 3); // 1, 2, 3 are the constructor parameters
</pre>
<p>
See the <code>ConstructorCalledMockTest</code> for an example.
</p>
<h3>Replace default class instantiator</h3>
<p>
For some reason (usually an unsupported JVM), it is possible that EasyMock isn't able to mock
a class mock in your environment. Under the hood, class instantiation is implemented with a factory
pattern. In case of failure, you can replace the default instantiator with:
</p>
<ul>
<li>The good old <code>DefaultClassInstantiator</code> which works well with Serializable classes
and otherwise tries to guess the best constructor and parameters to use.</li>
<li>You own instantiator which only needs to implement <code>IClassInstantiator</code>.</li>
</ul>
<p>
You set this new instantiator using <code>ClassInstantiatorFactory.setInstantiator()</code>.
You can set back the default one with <code>setDefaultInstantiator()</code>.
</p>
<p>
<b>Important:</b>
The instantiator is kept statically so it will stick between your unit tests. Make sure you
reset it if needed.
</p>
<h3>Serialize a class mock</h3>
<p>
A class mock can also be serialized. However, since it extends a serializable class, this class
might have defined a special behavior using for instance <code>writeObject</code>. These methods
will still be called when serializing the mock and might fail. The workaround is usually to call
a constructor when creating the mock.
</p>
<p>
Also, de-serializing the mock in a different class loader than the serialization might fail. It wasn't tested.
</p>
<h3>Class Mocking Limitations</h3>
<ul>
<li>To be coherent with interface mocking, EasyMock provides a built-in behavior
for <code>equals()</code>, <code>toString()</code>, <code>hashCode()</code> and <code>finalize()</code>
even for class mocking. It means that you cannot record your own behavior for
these methods. This limitation is considered to be a feature
that prevents you from having to care about these methods.
</li>
<li>Final methods cannot be mocked. If called, their normal code will be executed.
</li>
<li>Private methods cannot be mocked. If called, their normal code will be executed.
During partial mocking, if your method under test is calling some private methods,
you will need to test them as well since you cannot mock them.
</li>
<li>Class instantiation is performed using
<a href="http://objenesis.googlecode.com/svn/docs/index.html">Objenesis</a>.
Supported JVMs are listed
<a href="http://code.google.com/p/objenesis/wiki/ListOfCurrentlySupportedVMs">here</a>.
</li>
</ul>
<h2>
EasyMock Development
</h2>
<p>
EasyMock has been developed by Tammo Freese at OFFIS. It is maintained by Henri Tremblay
since 2007. The development of EasyMock is hosted on <a href="http://sourceforge.net/projects/easymock/">SourceForge</a>
to allow other developers and companies to contribute.
</p>
<p>
Class mocking (previously known as EasyMock Class Extension) was initially developed
by Joel Shellman, Chad Woolley and Henri Tremblay on the files section of Yahoo!Groups.
</p>
<p>
Thanks to the people who gave feedback or provided patches, including
Nascif Abousalh-Neto, Dave Astels, Francois Beausoleil, George Dinwiddie, Shane Duan,
Wolfgang Frech, Steve Freeman, Oren Gross, John D. Heintz, Dale King, Brian Knorr,
Dierk Koenig, Chris Kreussling, Robert Leftwich, Patrick Lightbody, Johannes Link,
Rex Madden, David McIntosh, Karsten Menne, Bill Michell,
Stephan Mikaty, Ivan Moore, Ilja Preuss, Justin Sampson, Markus Schmidlin, Richard Scott,
Joel Shellman, Jiří Mareš, Alexandre de Pellegrin
Shaun Smith, Marco Struck, Ralf Stuckert, Victor Szathmary, Bill Uetrecht,
Frank Westphal, Chad Woolley, Bernd Worsch,
Rodrigo Damazio, Bruno Fonseca, Ben Hutchison and numerous others.
</p>
<p>
Please check the <a href="http://www.easymock.org">EasyMock home page</a> for new versions,
and send bug reports and suggestions to the
<a href="mailto:easymock@yahoogroups.com?subject=EasyMock ${project.version} feedback">EasyMock Yahoo!Group</a>.
If you would like to subscribe to the EasyMock Yahoo!Group, send a message to
<a href="mailto:easymock-subscribe@yahoogroups.com">easymock-subscribe@yahoogroups.com</a>.
</p>
<h3>
EasyMock Version 3.1 (2011-11-10) Release Notes
</h3>
<p>
New in version 3.1:
</p>
<ul>
<li>NoClassDefFoundError on calling EasyMock.replay/reset/verify on an interface mock without cglib in the classpath (EASYMOCK-40)
</li>
<li>Can compile in Java 7 (capture methods for primitive types are renamed and deprecated) (EASYMOCK-100)
</li>
<li>Fix memory leak in cglib callback registration process (EASYMOCK-89)
</li>
<li>Ignore calls to finalize on a mock (EASYMOCK-21)
</li>
<li>MockBuilder.addMockedMethod should fail for final methods (EASYMOCK-44)
</li>
<li>Bridge method should not be considered by MockBuilder.addMockedMethod (EASYMOCK-90)
</li>
<li>Perform a smoke test with PowerMock to make sure it is still working (EASYMOCK-88)
</li>
<li>Add the class or interface name in error message for each invocation (EASYMOCK-104)
</li>
</ul>
<p>
New in version 3.0:
</p>
<ul>
<li>EasyMock CE is now merged into EasyMock (2325762)
</li>
<li>Add "boolean capture(...)" for completude (but I don't think it's useful)
</li>
<li>Can't answer by delegating to a protected method (2891256)
</li>
<li>Failure during recording phase can impact following tests (2914683)
</li>
<li>Return a specific error when null is recorded as return value on a method returning a primitive type (2936175)
</li>
<li>Can disable class mocking with <code>EasyMock.DISABLE_CLASS_MOCKING</code>
</li>
<li>Remove deprecated classes from EasyMock 1
</li>
<li>Should not fail on a mock not having a <code>toString</code> method (2937916)
</li>
<li>Improved error message when matchers are mixed with raw params during method recording (2860190)
</li>
<li>Check there are still results available in a recorded behaviour before trying to match with it (2940400)
</li>
<li>Allow to mock classes from an Eclipse plugin (2994002)
</li>
<li>Add <code>isNull(Class<T>)</code>, <code>notNull(Class<T>)</code> and <code>anyObject(Class<T>)</code> for easier generic handling (2958636)
</li>
</ul>
<p>
For older release notes, see <a href="Documentation.html">EasyMock 2 and EasyMock 2 Class Extension documentations</a>.
</p>
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