Top Most JUnit4 Annotations : Test Examples and Tutorial

JUnit4 Annotations are single big change from JUnit 3 to JUnit 4 which is introduced in Java 5. With annotations creating and running a JUnit test becomes more easy and more readable, but you can only take full advantage of JUnit4 if you know the correct meaning of  annotations used on this version and how to use them while writing tests. In this

Junit tutorial we will not only understand meaning of those annotations but also we will see examples of JUnit4 annotations. By the way this is my first post in unit testing but if you are new here than you may like post 10 tips to write better code comments and 10 Object oriented design principles for Programmer as well.

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Top Most Best Practices to write JUnit test cases in Java

JUnit best practices in Java

No doubt writing good JUnit test cases is a rare skill just like writing good Code. A good, well thought and well written JUnit test can prevent several production issues during initial development or later maintenance in Java application. Though one can only be perfect in writing JUnit test by practice and a level of business knowledge which is important to envision different scenarios on which a method gets called, some best practices or experience of other developer may help to guide other programmers. In this Java article I am sharing some JUnit tips and Junit best practices which I have learned and follow while writing unit tests using JUnit for Java programs. One of the book which helped me a lot is Pragmatic Unit Testing in Java with JUnit by Andrew Hunt and Dave Thomas,  This book shares lot of JUnit best practices which is worth reading and learning if you are serious about Unit testing using JUnit. Never undermine importance of automated testing and test cases written by Developer who writes the code and that's the reason many company are asking programmer to design, code and provide unit tests during there Java interviews. These JUnit best practices not just apply to JUnit but to any other testing framework as well like TestNG, they are more on testing and writing test cases which is more important skill than tool like JUnit or TestNG.

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Top Most How to write Unit Test in Java using JUnit4 in Eclipse and Netbeans

Writing Junit tests for Java classes in Eclipse and Netbeans IDE are super easy, and I will show you with that later in this JUnit tutorial. Before that, let’s revise what is unit test and why should you write them. Unit test is to test smaller unit of code, e.g. methods.  Writing unit test to test individual unit of code is one of the best development practice and helps to find bug earlier in development cycle. Though there are other unit testing framework available in Java e.g. TestNG, JUnit has it’s own place among Java developers. IMHO code review and unit testing are two most important practices for improving code quality and should always be followed during software development. Sad thing is that not every developer follows it; some programmer don’t write unit test due to ignorance and others due to laziness. Any way, it’s just start which take time, once you start writing unit tests, you will automatically start enjoying it. I have seen Java developers testing there code with main() method, but now they prefer to test them with JUnit testcases. I agree few initial tests are difficult because of knowledge and inertia and best way to approach is to start with simplest of JUnit tests. In this JUnit tutorial, I will show you how to write and execute JUnit test from Eclipse and Netbeans, two popular Java IDE. By the way, if you are looking for any good book on JUnit and unit testing, you should look Pragmatic Unit Testing in Java with JUnit, it's an amazing book and teaches a lot about both JUnit and unit testing in Java.

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Top Most JUnit 4 Tutorial - Test Exception thrown by Java Method with Example

One part of unit testing a Java method is checking exception thrown by that method. A Java unit test should verify correct exception thrown in exceptional case and no exception should be thrown in normal case. In JUnit 3.XX, there was no direct support to pass or fail a test based upon exception thrown by a Java method. JUnit4 address this issue and provides an easy, and readable way to test exception thrown by a Java method. There are many situations when you need to  test exception thrown by any method in Java. Classical example of this is testing API methods which should throw IllegalArgumentException if arguments passed to method are not matching to pre-conditions. In order to test exception thrown by any method in JUnit 4 you need to use @Test(expected=IllegalArgumentException.class)annotation. You can replace IllegalArgumentException.class with any other exception e.g. NullPointerException.class or ArithmeticException.class etc. Bottom line is that JUnit 4 will execute that test and check if method actually throws expected exception or not. If method throws expected exception, specified as "expected", than JUnit 4 will pass that test, but if method throws any other exception, or doesn't throw any exception than JUnit4 will fail that particular test.

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