JUnit

Outline
• What's JUnit ?
• Hierarchy for JUnit
• Examples

What's JUnit
• A unit test framework for Java
• Originated from xUnit
• An important component in test-driven
development (TDD)
o TDD comes from XP (eXtreme Programming)
o XP is a methodology to realize agile SW
development
Useful when the spec changes frequently.
Test case guarantees your SW quality
when you do refactor.

Hierarchy for JUnit (2/2)
• TestRunner
o Use to run the test & get/show the test result
• Test
o Define the interface for test
• TestCase (Implements the Test interface)
o A test case is a test method.
• TestSuite (Implements the Test interface)
o A test suite collects the test methods in TestCase class (the
method name's prefix must be "test")
o A test suite also collects the Tests (TestCase+TestSuite)
• TestResult
o Use to collect the test result.

Something you must know before UT
• Test Class
o The class you use to test the tested class.

• Tested Class
o The class you want to test.
To verify the correctness to the tested class,
the test class will invoke the tested class's method.

(Test Class) (Tested Class)
Origin2DPointTest.java Origin2DPoint.java

Examples (1/7)
1. TestCase
o A specific test method which is indicated when
invoking the constructor

2. TestSuite
o Collects all the test methods in TestCase

3. TestSuite (1+2)
o Collects the Tests (TestCase + TestSuite)

Examples (2/7)
• Directory structure for example
o tw/xxxx/shape/
Point.java
OriginPoint.java

o tw/xxxx/shape/tests
OriginPointTest.java
xxxx
location to junit

• Compile & Run
xxxx
xxxx

xxxx

Examples (3/7)
• Point.java
public class Point{
private int x;
private int y;

public Point(int x, int y){
this.x = x;
this.y = y;
}

public Point(){
this(0,0);
}

public int getX(){
return this.x;
}

public int getY(){
return this.y;
}
}

Examples (4/7)
• OriginPointTest.java
public class OriginPointTest extends TestCase{ public void testOriginY(){
private Point orignPoint; System.out.println("[testOriginY]");
assertEquals(0, orignPoint.getY());
public OriginPointTest(String name){ System.out.println("[[testOriginY]]");
super(name); }
}
public void prefixIsNotTest_testAbnormal(){
protected void setUp(){ System.out.println("[prefixIsNotTest_testAbnormal]");
System.out.println("[setUp]"); fail();
orignPoint = new OriginPoint(); System.out.println("[[prefixIsNotTest_testAbnormal]]");
System.out.println("[[setUp]]"); }
}
public static void main(String[] args){
protected void tearDown(){ TestCase testCase = new OriginPointTest("prefixIsNotTest_testAbnormal") ;
System.out.println("[tearDown]"); TestSuite testSuite = new TestSuite(OriginPointTest.class);
orignPoint = null; System.out.println("case 1");
System.out.println("[[tearDown]]"); TestRunner.run(testCase);
System.out.println("case 2");
} TestRunner.run(testSuite);
System.out.println("case 3");
public void testOriginX(){ testSuite.addTest(testCase);
System.out.println("[testOriginX]"); TestRunner.run(testSuite);
assertEquals(0, orignPoint.getX()); }
System.out.println("[[testOriginX]]"); }
}

Examples (5/7)
• Execution Result (Case 1)

Examples (6/7)

Examples (7/7)
setUp will be invoked
before each test method

tearDown will be invoked
testSuite = new
before each tested method
TestSuite(OriginPointTest.class);

testCase = new
OriginPointTest("prefixIsNotTest_testAbnormal")

Failure means a test case fail

Error means a test case
occurs exception

Sequence Diagram (1/2)
• A TestRunner run a TestCase.

Sequence Diagram (2/2)
• A TestRunner run a TestSuite.

run it recursively

Summary
• new TestCase("testMethod")
o run --> invoke the method "testMethod“

• new TestSuite(testCase.class)
o collects all the methods whose prefix is "test"
and add it as TestCase to the TestSuite.
o run --> invoke the method "run" in each TestCase.

• testSuite.addTest(...)
o testSuite.addTest(testCase)
o testSuite.addTest(testSuite2)

JUnit

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