Testing in Java Series
Last updated: June 5, 2025
Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.
Get started with mocking and improve your application tests using our Mockito guide:
Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.
Get started with understanding multi-threaded applications with our Java Concurrency guide:
Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.
But these can also be overused and fall into some common pitfalls.
To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:
Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:
Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.
I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.
You can explore the course here:
Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.
Get started with Spring Data JPA through the guided reference course:
Refactor Java code safely — and automatically — with OpenRewrite.
Refactoring big codebases by hand is slow, risky, and easy to put off. That’s where OpenRewrite comes in. The open-source framework for large-scale, automated code transformations helps teams modernize safely and consistently.
Each month, the creators and maintainers of OpenRewrite at Moderne run live, hands-on training sessions — one for newcomers and one for experienced users. You’ll see how recipes work, how to apply them across projects, and how to modernize code with confidence.
Join the next session, bring your questions, and learn how to automate the kind of work that usually eats your sprint time.
Yes, we're now running our only Summer Sale. All Courses are 30% off until 20th July, 2026:
Yes, we're now running our only Summer Sale. All Courses are 30% off until 20th July, 2026:
Explore how to use different Java-based testing tools through the guides below.
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JUnit
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Mockito
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Hamcrest
- Testing with Hamcrest
- Check if a List Contains Elements With Certain Properties in Hamcrest
- Hamcrest Common Core Matchers
- Hamcrest Text Matchers
- Using Hamcrest Number Matchers
- Check if a Variable Is Null Using Hamcrest
- Hamcrest Bean Matchers
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TestNG
- Introduction to TestNG
- Running a TestNG Project From the Command Line
- Custom Reporting with TestNG
- Continue the Test Even After Assertion Failure in TestNG
- Difference Between BeforeTest and BeforeMethod in TestNG
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Cucumber
- REST API Testing with Cucumber
- Cucumber Spring Integration
- Cucumber Data Tables
- Cucumber and Scenario Outline
- Passing List as Cucumber Parameter
- How to Ignore Scenarios in Cucumber
- Overriding Cucumber Option Values
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JMeter
- Intro to Performance Testing using JMeter
- Run JMeter .jmx File From the Command Line and Configure the Report File
- Analyzing JMeter Results
- Running Multiple Thread Groups in JMeter
- Basic Authentication in JMeter
- JMeter: Latency vs. Load Time
- Inserting Delays Between Requests in Apache JMeter
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AssertJ
- Introduction to AssertJ
- AssertJ Exception Assertions
- Ignoring Fields During Comparison Using AssertJ
- Extract Values using AssertJ in Java
- Using Conditions with AssertJ Assertions
- Custom Assertions with AssertJ
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Selenium
- Guide to Selenium with JUnit / TestNG
- Automated Browser Testing With Selenium
- Finding Element by Attribute in Selenium
- How to Handle Alerts and Popups in Selenium
- Retrieve the Value of an HTML Input in Selenium WebDriver
- Implicit Wait vs Explicit Wait in Selenium Webdriver
- Clicking Elements in Selenium using JavaScript
- Running Selenium Scripts with JMeter
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