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JUnit

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Unit Testing with JUnit

• If code has no automated test case written for it to prove that it works, it must be assumed not to work.

• An API that does not have an automated test case to show how it works must be assumed un-maintainable.

• Software without automated test cases cannot be economically refactored. Software that that cannot be refactored cannot be extended economically.

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Don't have the time for unit test?

• Productivity is directly related to the stability of your code base.– The fewer test cases you write, the less s

table your code base becomes.– You spend all your time fixing unintende

d side effects and bugs.

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Where to Get JUnit

• JUnit was written by Erich Gamma and Kent Beck.

• http://www.junit.org/index.htm

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System.out.println is Not Enough

• It is hard to tell if a complex system is working because so many System.out.println methods are printing so much garbage.

• Second, you must determine if something works by looking at a String scrolling by on a console. The string of text scrolling by may make sense the day you wrote it, but will it still make sense in three months?

• Third, when you make changes, things can break in unexpected ways.

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Overview of JUnit

• JUnit is a framework for writing unit tests.• A test case defines a fixture to run a

related set of tests. Typically, every class that you write should have a test case.

• A test fixture provides resources: primitive variables and objects that tests need to run.

• A test suite is a collection of related test cases.

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Practice• 1. Subclass junit.framework.TestCase.• 2. If we need fixture objects, override the setUp

() method.• 3. Define a number of tests that return void and

whose method name begins with test, such as testAdd(), testPut(), and testIterator().

• 4. If we need to release resources that were part of the fixture, override the tearDown() method.

• 5. If we need to group a related set of test cases, define a suite of tests.

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An examplepackage xptoolkit.junit.example;

import junit.framework.*;import java.util.Map;import java.util.HashMap;import junit.extensions.*;public class HashMapTest extends TestCase {

private Map testMap; private Map testMap2; public HashMapTest(String name) { super(name); }

public static Test suite() { return new TestSuite(HashMapTest.class); }

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public static void main (String[] args) { junit.textui.TestRunner.run (suite()); } private static final String APPLE_KEY = "AppleCEO"; private static final String APPLE_VALUE = "AppleCEO"; protected void setUp() { testMap = new HashMap(); testMap.put(APPLE_KEY, APPLE_VALUE); testMap.put("OracleCEO","Larry Ellison"); testMap2 = new HashMap(); testMap2.put("1", "1"); testMap2.put("2", "2"); }

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public void testPut(){ String key = "Employee"; String value = "Rick Hightower"; //put the value in testMap.put(key, value); //read the value back out String value2 = (String)testMap.get(key); assertEquals("The value back from the map ", value, value2); } public void testSize(){ assertEquals (2, testMap.size()); } public void testGet(){ assertEquals(APPLE_VALUE, testMap.get(APPLE_KEY)); assertNull(testMap.get("JUNK_KEY")); }

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public void testPutAll(){ testMap.putAll(testMap2); assertEquals (4, testMap.size()); assertEquals("1", testMap.get("1")); testGet(); } public void testContainsKey(){ assert("It should contain the apple key", testMap.containsKey(APPLE_KEY)); }

public void testContainsValue(){ assert(testMap.containsKey(APPLE_VALUE)); }

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public void testRemove(){ String key = "Employee"; String value = "Rick Hightower"; //put the value in testMap.put(key, value); //remove it testMap.remove(key); //try to read the value back out assertNull(testMap.get(key));

} }

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Explanation 1

• Step 1 is to define a class that derives junit.framework.

import junit.framework.*;...public class HashMapTest extends TestCase {

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Explanation 2

• Next, if our test case needs a fixture, we override the setUp() method

protected void setUp() { testMap = new HashMap(); testMap.put(APPLE_KEY, APPLE_VALUE); testMap.put("OracleCEO","Larry Ellison"); testMap2 = new HashMap(); testMap2.put("1", "1"); testMap2.put("2", "2"); }

the fixture the test case sets up is actually instances of the class under test: the HashMapclass. Garbage-collection will destroy the object.

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Explanation 3

• The HashMapTest class defines several tests to test the HashMap class.

• The JUnit framework uses reflection to look for methods whose names begin with test and uses them as test cases.

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Explanation 4

• It does this when we invoke the TestSuite constructor in the static suite() method,

public static Test suite() { return new TestSuite(HashMapTest.class); }

the composite design pattern

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Explanation 5

• assertEquals()• assertTrue()

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Explanation 6

• Note that the setUp() and tearDown() methods are called before and after every textX() method that is run.

• Because the setUp() method does not allocate any resources that need to be released, the HashMapTest does not need to override the tearDown() method.

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JUnit and Ant

• Copy junit.jar to Ant’s lib directory.<project name="currency" default="test" basedir="."> <property name="lib" value="./lib"/> <property name = "report" value="./report" /> <path id="lib1"> <pathelement location="."/> <fileset dir="${lib}"> <include name="**/*.jar"/> </fileset> </path> <target name="init"> <property name="outdir" value = "class"/> </target> <target name="prepare" depends="init"> <mkdir dir="${outdir}"/> <mkdir dir="${report}"/> </target>

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<target name="compile" depends="prepare"> <javac srcdir ="./src" destdir = "${outdir}"> <classpath refid="lib1"/> </javac> </target> <target name="test" depends="compile"> <junit printsummary = "true"> <formatter type="xml" /> <test name="TestCurrency" todir="${report}"/> <classpath> <pathelement location="${outdir}"/> </classpath> </junit> <junitreport todir="report"> <fileset dir ="${report}" > <include name = "TEST-*.xml"/> </fileset> <report format="frames" todir="${report}/html"/> </junitreport> </target> <target name="clean"> <delete dir="${report}"/> </target></project>

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Reading work

• http://junit.sourceforge.net/doc/cookbook/cookbook.htm