Java Testing Tools – 10 Best Practices For Writing Test Cases

Without Java, it isn’t easy to envision where today’s Big Data and Machine Learning projects would be at this point. It has been created to provide dynamic capabilities that weren’t available in traditional compiled languages for more than 25 years. Likewise, these skills typically weren’t available in traditional languages. It is now one of the server-side languages utilized extensively for projects involving both back-end and front-end development.

As a professional Java developer, you know the importance of testing your code. But what are the best practices for writing test cases? This blog post will explore ten tips for creating practical Java unit tests. Whether you’re just getting started with testing or looking to optimize your workflow, these tips will help you write better test cases and improve the quality of your code. Explore  Java Tutorial for complete information.

So read on and learn how to make the most of Java testing tools!

1. Utilize A Structure for Your Unit Testing 

Unit testing can be performed using any of Java’s many available frameworks. The most widely used testing frameworks are called TestNG and JUnit, respectively. The following are some of the essential features of JUnit and TestNG:

● Simple in both its installation and its operation.

● Allows the use of annotations

● Allows specific tests to be skipped and grouped together and run concurrently.

● Provides support for parameterized testing, also known as the execution of a unit test, by defining multiple values at the time of the test’s execution.

● Integrates with build technologies such as Ant, Maven, and Gradle, which enables automated test execution.

EasyMock is a mocking framework that may be used in conjunction with other unit testing frameworks such as JUnit and TestNG. EasyMock is not intended to be used as a standalone full-fledged framework. It merely provides the capability to generate mock objects to make testing easier. A DAO class that retrieves data from the database might be invoked, for instance, by a method we want to test on our end. In this particular scenario, EasyMock can be utilized to generate a MockDAO that returns hard-coded data. This allows us to quickly test the method we intend to use without worrying about accessing the database.

2. Use Test Driven Development 

Test-driven development, also known as TDD, is a process for developing software in which tests are generated initially based on the specifications before any coding is done. The test will initially be considered invalid because there is no code yet. After that, the bare minimum amount of code required to pass the test is written. After that, the code goes through a process of refactoring and optimization.

Instead of merely writing code first, which might not even meet the criteria, the goal is to write tests that cover all requirements. Test-driven development (TDD) is beneficial because it results in modular, simple, and easy-to-maintain code. As a result, the development process as a whole move along more quickly, and errors are easier to spot. Additionally, unit tests are generated by utilizing the TDD methodology.

However, TDD might not be the best option in every circumstance. For example, concentrating on the most uncomplicated design possible to pass the test cases and failing to plan can result in significant changes to the code when working on projects with complex designs. Additionally, the TDD methodology is challenging to use in environments where there is interaction with legacy systems, graphical user interface apps, or programs that collaborate with databases. Additionally, as the code is modified, the tests need to be brought up to date.

Therefore, before choosing a method for TDD, the above considerations are to be kept in mind, and a decision should be made according to the type of project being worked on.

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3. Measure Code Coverage 

Code coverage is the percentage of code executed when unit tests are executed. As a result of executing more of its source code during testing, code with high coverage typically has a lower probability of containing undetected errors. Among the most acceptable methods for determining code coverage are:

Use a code coverage tool such as Clover, Cobertura, JaCoCo, or Sonar. Using a tool can increase the quality of testing since these tools can identify untested sections of the code, allowing you to build new tests to cover these parts.

Whenever a new feature is added, write new tests promptly.

Ensure that there are test cases for all possible code branching, i.e., if/else statements.

The concat method below accepts a boolean value as input and appends the two strings passed in only if the boolean value is true:

public String concat(boolean append, String a,String b) {

        String result = null;

        If (append) {

            result = a + b;


        return result.toLowerCase();


The following is a test case for the above method:


        public void testStringUtil() {

      String result = stringUtil.concat(true, “Hello “, “World”);

      System.out.println(“Result is “+result);


In this instance, the test is run with the value true. When the test is performed, it will be successful. As all of the code in the concat method is performed, a code coverage tool will report 100 percent code coverage when executed. If the test is conducted with a false value, however, a NullPointerException will be thrown. Therefore, 100% code coverage is not a reliable indicator of whether all scenarios have been covered and the test is effective.

4. Externalize Test Data

Before JUnit4, test case data had to be hardcoded into the test case to be executed. This restricted that the test case code had to be updated to execute the test with alternative data. However, both JUnit4 and TestNG support externalizing the test data, allowing test cases to be executed with alternative datasets without modifying the source code.

The MathChecker class below has a method that checks if a number is odd:

public class MathChecker {

        public Boolean isOdd(int n) {

            if (n%2 != 0) {

                return true;

            } else {

                return false;




The following is a TestNG test case for the MathChecker class:

public class MathCheckerTest {

        private MathChecker checker;


        public void beforeMethod() {

          checker = new MathChecker();




        public void isOdd(int num) {

          System.out.println(“Running test for “+num);

          Boolean result = checker.isOdd(num);

          Assert.assertEquals(result, new Boolean(true));



5. Try To Use Assertions Instead Of Print Statements 

Numerous novice developers practice inserting a System.out.println statement following every line of code to ensure that the code is processed properly. Frequently, this habit expanded to unit tests, resulting in cluttered test code. In addition to the clutter, developers need manual intervention to examine the console output to determine whether the test performed correctly. Utilizing assertions that automatically reveal test outcomes is preferable.

The following StringUtil class is a simple class with one method that concatenates two input strings and returns the result:

public class StringUtil {

    public String concat(String a,String b) {

        return a + b;



The following are two-unit tests for the method above:


        public void testStringUtil_Bad() {

      String result = stringUtil.concat(“Hello “, “World”);

      System.out.println(“Result is “+result);



        public void testStringUtil_Good() {

      String result = stringUtil.concat(“Hello “, “World”);

      assertEquals(“Hello World”, result);


6. Build Tests That Have Deterministic Results

Some procedures do not produce a predictable output, meaning that the output cannot be predicted in advance and varies each time. Consider the following code, which has a complex function and a method for calculating the execution time (in milliseconds) of the complex function:

public class DemoLogic {

    private void veryComplexFunction(){

        //This is a complex function that has a lot of database access and is time consuming

        //To demo this method, I am going to add a Thread.sleep for a random number of milliseconds

        try {

            int time = (int) (Math.random()*100);


        } catch (InterruptedException e) {

            // TODO Auto-generated catch block




    public long calculateTime(){

        long time = 0;

        long before = System.currentTimeMillis();


        long after = System.currentTimeMillis();

        time = after – before;

        return time;



In this situation, the calculateTime method will return a different result each time it is called. As the function’s output is variable, writing a test case for this method would be ineffective. Therefore, the test function will not validate the output for any specific run.

7. Test Negative Scenarios and Borderline Cases

Frequently, developers invest a great deal of time and energy in building test cases to guarantee that the application functions as planned. However, it is also essential to test negative test scenarios. A negative test case assesses a system’s ability to handle incorrect data. In addition to testing for alphabetic values, the following negative test scenarios must be examined:

● The user enters non-alphanumeric data such as special characters.

● User specifies a blank value

● User specifies a value greater than or less than eight characters

Similarly, a borderline test case evaluates the system’s performance under severe conditions. For instance, if a user is expected to provide a numeric number between 1 and 100, 1 and 100 are the boundary values, and it is crucial to test the system for these values.

8. Tests Should Be Simple

There are several methods we might use to be highly particular in the accuracy of our tests. One of these is to limit the cyclomatic complexity of your tests. Cyclomatic complexity is a code statistic representing the number of potential execution routes for a given method. A piece of code with less complexity is simpler to comprehend and maintain, which reduces the likelihood that developers would make errors while working on it.

9. Don’t Couple Your Tests with Implementation Details

You should prevent unit tests from overly tied to the code they are testing. In this sense, they are more adaptable to change, allowing developers to tweak internal implementation and rework as necessary while receiving vital feedback and a safety net.

10. Tests Should Be Readable

This recommended practice overlaps with the one about keeping your testing simple. Developers are more likely to create bugs if tests are difficult to comprehend. However, this is not the only reason we promote test readability.

Test cases also serve as documentation. And they are the ideal sort of documentation since they are executable and do not fall out of sync with their subject matter. However, for the team to reap the benefits of these executable specifications, they must be readable.


Developing a Better Test Case Efficiency is not a notion that can be defined straightforwardly; instead, it is an activity that may be accomplished by following a delicate procedure and engaging in consistent practice.

Because it is the most effective method for reaching higher levels of success in the quality industry, the testing team should never get sick of participating in enhancing activities of this kind. This has been demonstrated in a large number of international testing organizations on important applications and projects.

Java testing tools are a vital part of the software development process. By writing test cases and following best practices, you can ensure that your code is error-free and meets the requirements set by your stakeholders. The 10 tips we’ve shared should help you create high-quality test cases for your Java applications. 

Author Bio:

I am Korra Shailaja, Working as a Digital Marketing professional & Content writer in MindMajix Online Training. I Have good experience in handling technical content writing and aspire to learn new things to grow professionally. I am an expert in delivering content on the market demanding technologies like Mulesoft Training, Dell Boomi Tutorial, Elasticsearch Course, Fortinet Course, PostgreSQL Training, Splunk, Success Factor, Denodo, etc.

James Morkel

Tech website author with a passion for all things technology. Expert in various tech domains, including software, gadgets, artificial intelligence, and emerging technologies. Dedicated to simplifying complex topics and providing informative and engaging content to readers. Stay updated with the latest tech trends and industry news through their insightful articles.

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