Junit 4.0 with examples

1. Junit 4.0
-Pallavi Khandekar

2. What is JUnit?
• JUnit is an open source regression testing framework.
• Written by Erich Gamma and Kent Beck
• Part of xUnit family. (e.g. NUnit, CPPUnit etc)
• Eclipse includes JUnit. You can also run JUnit outside of
Eclipse using JUnit’s window.
• Home page:
– http://junit.org.

3. Unit Testing
• Key element in Extreme Programming.
• Focuses on fundamental block at a time.
• Helps to find problems early.
• Easy to maintain.
• Simplifies Integration testing.

4. Unit Testing (contn..)
• Proves as documentation of System(proves that
system works).
• Leads to high quality code, higher productivity and
low maintenance.
• JUnit helps developer write unit tests as they
develop the system.
• Makes writing test cases easy and painless.

5. Application of JUnit:
Test Driven Development (TDD)
TDD = TFD + Refactoring

6. Principles of testing frameworks.
• Each unit test should run independently of all other
unit tests.
• Errors must be detected and reported test by test.
• It must be easy to define which unit tests will run.
• It should be easy to add unit tests.
• Help us reduce the cost of writing tests by reusing
code.

7. Terminologies in Junit
•A test case tests single method.
Runner Result
Test Suite •A unit test tests all methods in a class.
Unit Test 3 •A test suite combines unit test cases.
• Test fixtures provide software support for all
Unit Test 2 operations. (e.g. mock database)
•The test runner runs the unit test or entire test
suite.
Unit Test 1
•The test result collects & summarizes all test
information of tests e.g. a test can pass , fail
Test Fixtures (assertion error) and error (exception is thrown)

8. Important Classes and Annotation of
Junit Framework
Test : - Annotation that tells that the attached method is a test method.
Suite :- A class which runs all the unit test cases defined in @SuiteClasses
annotation.
Assert:- Assert class provides lot of assert methods which we can use to throw an
exception if the proposition to it fails.
Runner:- It runs a unit test/ suite and notifies RunNotifier of the significant
event.
RunListener :- Listens to events triggered by Runner. (e.g. Test Begin, Test End etc)
Result:- Collects and summarizes all the information from multiple tests.

9. Annotations

10. Test Methods

11. Simple Case Study
• Create a Java project in Eclipse with two folders
– src : will hold all the source code files
– test: will hold all the test cases
• Write a method ‘multiply’ in Java class.
/** This method multiplies the two integers.
* @param x : first integer to be multiplied.
* @param y : second integer to be multiplied.
* @return integer product
*/
public int multiply(int x, int y)
{
return x/y;
}

12. Simple Case Study (cond..)
• Create a JUnit test case in ‘test’ folder . (File->
New - > JUnit Test Case)
• Add method to test the ‘multiply’ method.
@Test
/**
* test method to test Multiply functionality.
*/
public void testMultiply() {
MyFirstClass tester = new MyFirstClass();
assertEquals("Result", 50, tester.multiply(5, 10));
}

13. Simple Case Study (cond..)
• To execute the test case just right click and say Run as Junit
test.
The bar will be red if
the test fails.
It also displays in
Failure trace the
expected value and
actual output of
function in test.

14. Example 2
public class TestCounter {
//Declare Counter
Counter objCounter; Test class for Counter.
@Before Note*:
public void setUp()
Each test begins with a brand new
{
objCounter = new Counter(); Counter object. So for the
} decrement method we compared
return value with -1.
@Test
public void testIncrement() { Each tests are independent of each
assertTrue(objCounter.increment() == 1); other.
assertTrue(objCounter.increment() == 2);
}
@Test
public void testDecrement() {
assertTrue(objCounter.decrement() == -1);
}
}

15. public class Counter {
Example 2
This is actual Counter Class.
int intCounter = 0;
//increament's counter
public int increment(){
return intCounter+=1;
}
//decreament's counter
public int decrement(){
return intCounter-=1;
}
//return's counter
public int getIntCounter()
{
return intCounter;
}
}

16. Expected Exception handling TestCases
Method to test: Test Case
public class ArrayManipulations { int[] a1= {1,2,3,4,5,6,7,8,9,10}; //length=10
int[] b1= {0,2,4,6,8,10}; //length 6
public void Bar(int a[],int b[], int n) @Test(expected =
{ ArrayIndexOutOfBoundsException.class)
a[0]=b[0]; public void testBarPreconditions() {
int i=1; ArrayManipulations tester = new
while (i<n) { ArrayManipulations();
a[i]=b[i]+a[i-1];
a[i-1]=0; int n = 11;
i=i+1; tester.Bar(a1, b1, n);
} }
}
}

17. Test Suites
• Test Suite is created from
import org.junit.runner.RunWith; New->Others->Junit->Junit Test
import org.junit.runners.Suite; Suite
import org.junit.runners.Suite.SuiteClasses;
•The suite will run all tests in
classes mentioned in
@RunWith(Suite.class) @SuiteClasses
@SuiteClasses({ MyTestClass.class, TestCounter.class })
public class AllTests { •We can add on the .class
names whenever a new unit
} test is created.

18. Advantages of Junit framework
• Alternate front ends to display results of tests are available
like command line, AWT and Swing.
• Separate class loaders for each unit test to avoid side
effects.
• Provides methods like setUp and tearDown for standard
resource initialization.
• A set of assert methods to check results of tests.
• Integration with popular tools such as Ant and Maven and
IDE’s like Eclipse and Jbuilder.

19. Disadvantages of Junit Framework
• Cannot do dependency testing. TestNG allows this.
• Not suitable for higher level testing. (Large test suites.)

20. References
• http://junit.org.
• Javadoc: http://kentbeck.github.com/junit/javadoc/latest/
• Book: Junit in Action by Vincent Massol with Ted Husted

21. Thank You !!!
Questions ?