關(guān)于單元測(cè)試，模擬對(duì)象一直是不可缺少的，尤其對(duì)于復(fù)雜的應(yīng)用來說。
?????? 這么多的模擬對(duì)象框架中，個(gè)人覺得比較好用的當(dāng)屬EasyMock了。當(dāng)然JMock也不錯(cuò)。
?????? 下面簡(jiǎn)單介紹一下EasyMock?。（基本翻譯EasyMock的文檔，可能有些地方不是很恰當(dāng)）
?????
???????EasyMock 2
主要用于給指定的接口提供模擬對(duì)象。
模擬對(duì)象只是模擬領(lǐng)域代碼直接的部分行為，能檢測(cè)是否他們?nèi)缍x中的被使用。使用
Mock
對(duì)象，來模擬合作接口，有助于隔離測(cè)試相應(yīng)的領(lǐng)域類。
創(chuàng)建和維持
Mock
對(duì)象經(jīng)常是繁瑣的任務(wù)，并且可能會(huì)引入錯(cuò)誤。
EasyMock 2
動(dòng)態(tài)產(chǎn)生
Mock
對(duì)象，不需要?jiǎng)?chuàng)建，并且不會(huì)產(chǎn)生代碼。
有利的方面：
不需要手工寫類來處理
mock
對(duì)象。
支持安全的重構(gòu)
Mock
對(duì)象：測(cè)試代碼不會(huì)在運(yùn)行期打斷當(dāng)重新命名方法或者更改方法參數(shù)。
支持返回值和例外。
支持檢察方法調(diào)用次序，對(duì)于一個(gè)或者多個(gè)
Mock
對(duì)象。
不利的方面：
2.0
僅使用于
java 2
版本
5.0
或者以上
????
??? 以一個(gè)例子來說明如何使用EasyMock:
???假設(shè)有一個(gè)合作接口Collaborator：
??????????? 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); }
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我們主要的測(cè)試類為：
package org.easymock.samples;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set; public class ClassUnderTest {??? private Set<Collaborator> listeners = new HashSet<Collaborator>(); ??? private Map<String, byte[]> documents = new HashMap<String, byte[]>(); ??? public void addListener(Collaborator listener) {
??????? listeners.add(listener);
??? }??? public void addDocument(String title, byte[] document) {
??????? boolean documentChange = documents.containsKey(title);
??????? documents.put(title, document);
??????? if (documentChange) {
??????????? notifyListenersDocumentChanged(title);
??????? } else {
??????????? notifyListenersDocumentAdded(title);
??????? }
??? }??? public boolean removeDocument(String title) {
??????? if (!documents.containsKey(title)) {
??????????? return true;
??????? }??????? if (!listenersAllowRemoval(title)) {
??????????? return false;
??????? }??????? documents.remove(title);
??????? notifyListenersDocumentRemoved(title); ??????? return true;
??? } ??? public boolean removeDocuments(String[] titles) {
??????? if (!listenersAllowRemovals(titles)) {
??????????? return false;
??????? }??????? for (String title : titles) {
??????????? documents.remove(title);
??????????? notifyListenersDocumentRemoved(title);
??????? }
??????? return true;
??? }??? private void notifyListenersDocumentAdded(String title) {
??????? for (Collaborator listener : listeners) {
??????????? listener.documentAdded(title);
??????? }
??? }??? private void notifyListenersDocumentChanged(String title) {
??????? for (Collaborator listener : listeners) {
??????????? listener.documentChanged(title);
??????? }
??? }??? private void notifyListenersDocumentRemoved(String title) {
??????? for (Collaborator listener : listeners) {
??????????? listener.documentRemoved(title);
??????? }
??? }??? private boolean listenersAllowRemoval(String title) {
??????? int result = 0;
??????? for (Collaborator listener : listeners) {
??????????? result += listener.voteForRemoval(title);
??????? }
??????? return result > 0;
??? }??? private boolean listenersAllowRemovals(String[] titles) {
??????? int result = 0;
??????? for (Collaborator listener : listeners) {
??????????? result += listener.voteForRemovals(titles);
??????? }
??????? return result > 0;
??? }}
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第一個(gè)Mock 對(duì)象
我們將創(chuàng)建test case 并且圍繞此理解相關(guān)的EasyMock 包的功能。第一個(gè)測(cè)試方法，用于檢測(cè)是否刪除一個(gè)不存在的文檔，不會(huì)發(fā)通知給合作類。
??????????package org.easymock.samples; ? import junit.framework.TestCase; ? public class ExampleTest extends TestCase {? ??? private ClassUnderTest classUnderTest; ??? private Collaborator mock; ? ??? protected void setUp() {??????? classUnderTest = new ClassUnderTest(); ??????? classUnderTest.addListener(mock); ??? } ? ??? public void testRemoveNonExistingDocument() {??? ????????// This call should not lead to any notification ???? ???// of the Mock Object: ????????classUnderTest.removeDocument("Does not exist");??? } }
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????對(duì)于多數(shù)測(cè)試類，使用EasyMock 2,我們只需要靜態(tài)引入org.easymock.EasyMock的方法。?????? ?import static org.easymock.EasyMock.*; import junit.framework.TestCase; ? public class ExampleTest extends TestCase { ? ??? private ClassUnderTest classUnderTest; ??? private Collaborator mock; ??? }
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?????
為了取得Mock 對(duì)象，需要：
l???????? 創(chuàng)建Mock 對(duì)象從需要模擬的接口
l???????? 記錄期待的行為
l???????? 轉(zhuǎn)換到Mock對(duì)象，replay狀態(tài)。
例如：????? ?protected void setUp() {??? ????mock = createMock(Collaborator.class); // 1 ??????? classUnderTest = new ClassUnderTest(); ??????? classUnderTest.addListener(mock); ??? }
?public void testRemoveNonExistingDocument() {??????? // 2 (we do not expect anything) ??????? replay(mock); // 3 ??????? classUnderTest.removeDocument("Does not exist");??? }
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??
在執(zhí)行第三步后，mock 為Collaborator接口的Mock對(duì)象，并且期待沒有什么調(diào)用。這就意味著，如果我們改變ClassUnderTest去調(diào)用此接口的任何方法，則Mock對(duì)象會(huì)拋出AssertionError：
???????? ?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) ??? ...
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增加行為
??????
讓我們開始第二個(gè)測(cè)試。如果document被classUnderTest增加，我們期待調(diào)用
mock.documentAdded()在Mock對(duì)象使用document的標(biāo)題作為參數(shù)：??public void testAddDocument() {?????? ?mock.documentAdded("New Document"); // 2??????? replay(mock); // 3 ??????? classUnderTest.addDocument("New Document", new byte[0]); ????}
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如果classUnderTest.addDocument("New Document", new byte[0])調(diào)用期待的方法，使用錯(cuò)誤的參數(shù)，Mock對(duì)象會(huì)拋出AssertionError:?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) ??? ...
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同樣，如果調(diào)用多次此方法，則也會(huì)拋出例外：
?java.lang.AssertionError: ??Unexpected method call documentAdded("New Document"):??? documentAdded("New Document"): expected: 1, actual: 1 (+1)??? 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) ??? ...
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驗(yàn)證行為
?????? 當(dāng)我們指定行為后，我們將驗(yàn)證實(shí)際發(fā)生的。當(dāng)前的測(cè)試將會(huì)判斷是否Mock對(duì)象會(huì)真實(shí)調(diào)用。可以調(diào)用verify(mock)來山正是否指定的行為被調(diào)用。
?public void testAddDocument() {??????? mock.documentAdded("New Document"); // 2 ????????replay(mock); // 3 ??????? classUnderTest.addDocument("New Document", new byte[0]);?????? ?verify(mock); ??? }
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如果失敗，則拋出AssertionError
期待明顯數(shù)量的調(diào)用
到現(xiàn)在，我們的測(cè)試只是調(diào)用一個(gè)簡(jiǎn)單的方法。下一個(gè)測(cè)試將會(huì)檢測(cè)是否已經(jīng)存在document導(dǎo)致mock.documentChanged()調(diào)用。為了確認(rèn)，調(diào)用三次
?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); ??? }
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為了避免重復(fù)的mock.documentChanged("Document"),EasyMock提供一個(gè)快捷方式。可以通過調(diào)用方法expectLastCall().times(int times)來指定最后一次調(diào)用的次數(shù)。
??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); ??? }
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指定返回值
?????? 對(duì)于指定返回值，我們通過封裝expect(T value)返回的對(duì)象并且指定返回的值，使用方法andReturn(Object returnValue)于expect(T value).返回的對(duì)象。
例如：
?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); ??? } ? ??? 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); ??? }
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取代expect(T value)調(diào)用，可以通過expectLastCall().來代替?expect(mock.voteForRemoval("Document")).andReturn((byte) 42);
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等同于
?mock.voteForRemoval("Document");expectLastCall().andReturn((byte) 42);
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處理例外
對(duì)于指定的例外(更確切的:Throwables)被拋出，由expectLastCall()和expect(T value)返回的對(duì)象，提供了方法andThrow(Throwable throwable)。方法不得不被調(diào)用記錄狀態(tài)，在調(diào)用Mock對(duì)象后，對(duì)于此指定了要拋出的Throwable。
基本的方法，已經(jīng)說完了，當(dāng)然這不能完全說明EasyMock的使用。更多的因素請(qǐng)參考EasyMock的文檔
http://www.easymock.org/Documentation.html
posted on 2006-09-20 20:38
布衣郎 閱讀(3078)
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