How to Use Java Integration Testing

Unit testing can be used to mock all the dependencies of a single Java class in order to isolate it from the rest of the system. This way the class under test is in a controlled environment where you can test its own business logic with nothing else in the way. There are times, however, when you should not use mocking during testing. For these cases, you need Java integration testing. Read on to learn: 

What is a Java Integration Test?

While there is no hard and fast definition, a Java integration test generally:

• Uses the database
• Uses the network
• Uses an external system (e.g., a queue or a mail server)
• Reads/writes files or performs other I/O

Sometimes, there isn’t a clear distinction between an integration test and a unit test. A basic rule of thumb is that a Java integration test meets the following criteria:

• A test uses the database
• A test uses the network
• Uses an external system (e.g. a queue or a mail server)
• Reads/writes files or performs other I/O

Unit Test vs. Integration Test

The chart below breaks down the differences between Java unit tests versus Java integration tests.

When to Use Java Integration Testing

Java integration testing should be used when you are interested in the interface of this class with its dependencies. By doing so, you zoom out from a single class to testing a component of the system. This is appropriate if the system is built on multiple classes or uses other systems, e.g., a database or a queue.

Java Integration Testing Best Practices

While there may not be a hard-and-fast definition for what comprises a Java integration test, there are best practices for implementing them and what to do if and when they fail.   

1. Use Detailed Logging

The use of detailed logging must be accounted for when conducting Java integration tests. When a unit test fails it is very easy to understand why since the scope is very narrow. When an integration test fails it’s often not so simple. Because an integration test by definition is based on many components and a specific data flow, identifying the failure cause is not always straightforward. Using detailed logging statements can help alleviate this problem. They’re always needed in an Enterprise application regardless of unit tests. This way, when an integration test fails you can examine the logs and understand if the issue is in the code or in an external resource used by the test.

2. Don't Use Java Integration Testing and Java Unit Testing Concurrently

This is the most important aspect of unit tests. In a large enterprise application, integration and unit tests must be handled differently. Here’s an all-too-common scenario: New developers simply declare that “writing unit tests is a waste of time.” They’re right from their point of view, since nobody wants to work with a broken test suite, but this is a situation that needs to be avoided. 

3. Split Unit and Integration Tests

There are many ways to split unit and integration tests, including using the Maven failsafe plugin. Unit tests should follow the naming convention introduced in the first part of this series. Unit test classes are named with “name of class + Test”. Then they are placed in the test directory of the Maven project structure. The unit tests are executed automatically when the test goal is run. Next you should add the failsafe plugin in your pom.xml file.

  …
  
    
      …
      
        org.apache.maven.plugins
        maven-failsafe-plugin
        2.13
        
          
            integration-test
            
              integration-test
            
          
          
            verify
            
              verify
            
          
        
      
    
  

Your integration tests have a different naming convention, however. They are named as “name of class + IT”. IT stands for Integration Test. Now the test goal will ignore them. Instead these tests will be executed by the integration-test goal which is a built-in goal into Maven. Below is a table that summarizes this split.

How to Run Java Integration Tests in Your Build Process

Now that all these changes are done, you have great flexibility on how you run unit tests. Most importantly, your build server (e.g. Jenkins) should contain a mixture of jobs that deal with both kinds of tests. Here is a overview of suggested jobs.

The suggested workflow is the following:

1. Developers run the test goal during development
2. Developers run the test goal before any commit
3. Developers run the integration-test goal before a major commit with many side effects
4. Build server compiles code and runs the test goal every 15-30 minutes (main build)
5. Build server compiles code and runs the integration-test goal every day (integration build)
6. Build server compiles code and runs the integration-test goal before a release to QA

With this workflow it is clear that developers get fast feedback from the unit tests so anything that breaks can be fixed immediately. The boring process of running integration tests is left to the build server which runs them automatically in a well defined schedule.

Java Integration Testing Frameworks

As we mentioned at the beginning of the article, developers often utilize a Java integration testing framework. A few of the more popular Java integration testing frameworks include Arquillian, DbUnit, and JUnit

• Arquillian - a Java integration testing framework specific to Java EE
• DbUnit - as the name implies, DbUnit can run both unit and integration tests
• JUnit - while most use JUnit for unit testing, many use JUnit for integration testing

Curious about what your Java development peers are using in their Java development environments? Find out in the 2025 Java Developer Productivity Report. 

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Final Thoughts

Implementing Java integration testing can save your organization development time.  Compound those time efficiency savings by eliminating rebuilds and redeploys with JRebel and save upwards of a month of development time annually. 

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