JUnit- Features, Uses, and Best Practices

Software testing is one of the important aspects in making the software worthwhile. Just imagine you have given your best to come up with a spectacular output and suddenly the software crashes!

For most of us, it’s a nightmare!

So, software testing is done to determine whether a particular software is fit for use. It ensures data safety and saves time by making the software free from unnecessary bugs and ensure you deliver the output in time.

Out of various testing methodologies, unit testing is the one which involves the testing of minor components or units of the source code. Here, testing the units can be taken as the smallest part of an application that can be tested.

What is JUnit?

JUnit is not an uncommon term among techies. Avid Java programmers know it is a unit testing framework designed exclusively for Java.

So far, JUnit has maintained its unique role in the development of test-driven development frameworks. It allows to write repeatable tests and is linked as a JAR file at the time of compilation.

A survey was conducted across 10,000 Java projects in 2013 and hosted in GitHub was found that JUnit (clubbed with slf4j-api), was the most used external library. Each one among the array of libraries was used by 30.7% of projects.

What are JUnit test fixtures?

A test fixture in the world of JUnit is nothing but a Java object. When it comes to older versions of JUnit, the fixtures had to be inherited from ‘junit.framework.TestCase’. But when it comes to the newer version, such as JUnit 4, the same method should be annotated with the annotation- @Test.

JUnit Best Practices:

JUnit is a unit toolkit. It can help in developing good and robust tests if it is handled diligently keeping its idiosyncrasies in mind. This article contains various information that will keep you safe from a nightmare.

Here, two of the most useful additional features will also be evaluated:

  • A new ‘TestCase’ that is very useful in multiple threads.
  • A unique mechanism of creating test suites automatically from classfiles in a filesystem.

List of Don’t(s):

To get the best of JUnit features, the user must avoid doing this:

Data should not be loaded from Hard Coded Locations:

Let us consider this case:

Public void setUp () {

FileInpitStream inp (“”C:\\TestData\\dataSet1.dat””);


This code relies on the data set located in ‘C:\\TestData’ path.

Assuming this could be a mistake in two situations:

  • The tester does not get the flexibility to store data in that location and he has to store it in another disk.
  • The tests run on a different platform such as Unix.

It could have a solution:

Public void setUp () {

FileInpitStream inp (“”dataSet1.dat””);


However, this solution for the specified test depends upon running the test from the same directory as the test data. When multiple test cases assume this, it becomes difficult to integrate them into a single test suite without changing the directory used currently.

Writing Test Cases Should Be Avoided with Side Effects:

Test Cases with side effects show up two problems:

  • They are liable to affect data that other test cases depend upon.
  • Tests can only be repeated manually.

Given the first condition, individual TestCase may operate correctly. However, incorporating it into a TestSuite, it might fail other TestCases. The biggest challenge that comes here is, it is difficult to diagnose the failure mode and the location of the error could be far from test failure.

TestCase in the second condition come up with a chance that some system states would be updated, and hence, they cannot be run once again without manual involvement.

Here, manual involvement must be done with proper care. It should be properly documented. Also, there is a chance that the tests could no longer be run in an unattended mode, hence putting a limit to the flexibility to run the tests automatically as a part of a periodic test run.

List of Do(s):

For a successful test, the following are a couple of things that should be taken care of:

  • Tests and Source Codes Must Be Kept In The Same Location:

If this is done, both test and class can be easily compiled during a build. The user is thus forced to keep tests and classes synchronized during the process of development.

  • Tests Should Be Named Properly

Consider the name of the test is ‘TestClassUnderTest’. So, the TestCase for the class ‘MessageLog’ will become ‘TestMessageLog’. Thus, when a test case tests a class, it becomes simple to work. The names of the test methods should explain what they test on this list:

  • testLoggingEmptyMessage()
  • testLoggingWarningMessage()
  • testLoggingNullMessage()
  • testLoggingErrorMessage()

When the naming is done properly, the code readers can easily understand the purpose of each test.

There is a significant change in the uses and capabilities of JUnit framework with every new version released in the market. So, in order to run a test successfully, the user must analyze the capabilities of each version and code it in a way that the code readers should easily understand.

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