JUnit & JUnit Testing

Overview

• Large applications can have 100s of code files and millions of lines of code, Inorder to checkapp behaviour against expected behaviour we do testing.
• Integration Testing: Deploy the Complete application by deploying the war or jar and test. This is also called as system testing.
• Unit Testing: Test specific units of application code independently. Ex: Testing a specific method or group of methods.
• Advantages of Unit testing:
  • Find bugs early(run under CI)
  • Easy to fix bugs
  • In Integration testing when the bug arises it difficult to find which method is causing an issue. In unit testing specif method is responsible for the bug and reduces the cost in the long run.
• Note: Integration+Unit testing should be done for better bug free code.

Junit Annotations

• JUnit Annotations is a special form of syntactic meta-data that can be added to Java source code for better code readability and structure. Variables, parameters, packages, methods and classes can be annotated. Annotations were introduced in Junit4, which makes Java code more readable and simple.

S.no	Annotations	Description
1.	@Test	This annotation is a replacement of org.junit.TestCase which indicates that public void method to which it is attached can be executed as a test Case.
2.	@Before	This annotation is used if you want to execute some statement such as preconditions before each test case.
3.	@BeforeClass	This annotation is used if you want to execute some statements before all the test cases for e.g. test connection must be executed before all the test cases.
4.	@After	This annotation can be used if you want to execute some statements after each Test Case for e.g resetting variables, deleting temporary files ,variables, etc.
5.	@AfterClass	This annotation can be used if you want to execute some statements after all test cases for e.g. Releasing resources after executing all test cases.
6.	@Ignores	This annotation can be used if you want to ignore some statements during test execution for e.g. disabling some test cases during test execution.
7.	@Test(timeout=500)	This annotation can be used if you want to set some timeout during test execution for e.g. if you are working under some SLA (Service level agreement), and tests need to be completed within some specified time.
8.	@Test(expected=IllegalArgumentException.class)	This annotation can be used if you want to handle some exception during test execution. For, e.g., if you want to check whether a particular method is throwing specified exception or not.

JUnit Assert Class

• This class provides a bunch of assertion methods useful in writing a test case. If all assert statements are passed, test results are successful. If any assert statement fails, test results are failed.

S.no	Method	Description
1.	void assertEquals(boolean expected, boolean actual)	It checks whether two values are equals similar to equals method of Object class
2.	void assertFalse(boolean condition)	functionality is to check that a condition is false.
3.	void assertNotNull(Object object)	assertNotNull functionality is to check that an object is not null.
4.	void assertNull(Object object)	assertNull functionality is to check that an object is null.
5.	void assertTrue(boolean condition)	assertTrue functionality is to check that a condition is true.
6.	void fail()	If you want to throw any assertion error, you have fail() that always results in a fail verdict.
7.	void assertSame([String message])	assertSame functionality is to check that the two objects refer to the same object.
8.	void assertNotSame([String message])	assertNotSame functionality is to check that the two objects do not refer to the same object.