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InfoQ Homepage News Test Well and Prosper: The Great Java Unit-Testing Frameworks Debate

Test Well and Prosper: The Great Java Unit-Testing Frameworks Debate

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A recent post in Reddit sparked a debate between supporters of JUnit and Spock testing frameworks, based on a blog post by Jakub Dziworski with the central theme, “What’s wrong with JUnit?”. It appears that every GitHub repository includes unit tests built with JUnit, which should come as no surprise since JUnit has been around for over 15 years. Yet, Spock continues to chip away.

JUnit was created by Kent Beck, creator of eXtreme programming, and Erich Gamma,co-author of Design Patterns: Elements of Reusable Object-Oriented Software, and it quickly became a defacto standard in unit testing, with ports and clones in nearly every popular programming language. However, JUnit’s features have been questioned over the years resulting in new unit-testing frameworks, such as TestNG and Spock.


TestNG was created by Cédric Beust, co-author of Next Generation Java Testing: TestNG and Advanced Topics, in 2004. According to the TestNG website, “TestNG is a testing framework inspired from JUnit and NUnit but introducing some new functionalities that make it more powerful and easier to use…”. Beust maintains on his website , “I started TestNG out of frustration for some JUnit deficiencies which I have documented on my weblog here and here.”


In his blog post, Dziworski questions using JUnit combined with a third-party mocking framework. He states, “Java combined with those frameworks makes it rather hard to write and read tests in medium and large sizes projects.” He goes on to say, “If tests are hard to write we usually think of them as something painful and start to neglect them. Avoiding or delaying writing tests leads to the situation where application cannot be trusted anymore. We then become afraid of making any changes because another part of the app might break in some bizarre way.”

At a recent Java Hellenic User Group meeting, Kostis Kapelonis, author of Java Testing with Spock, offered a presentation where he compared JUnit with Spock.

Spock was created by Peter Niederwieser, Principal Engineer at Gradleware, in 2008. While inspired by JUnit, Spock’s features are more than just an extension of JUnit:

  • Tests are written in Groovy which can test code written in Java.

  • A built-in mock framework eliminates the need to import third-party frameworks.

  • The ability to provide custom names for tests.

  • Predefined behavior-driven blocks (given:, when:, then:, expect:, etc.) for establishing tests.

  • Use of data tables eliminates the need to use data structures.

The following code snippet (as shown in the Reddit post) demonstrates some of these features:

1 class Math extends Specification {
2     def "maximum of two numbers"(int a, int b, int c) {
3         expect:
4         Math.max(a, b) == c

5         where:
6         a | b | c
7         1 | 3 | 3   // passes
8         7 | 4 | 4   // fails
9         0 | 0 | 0   // passes

This simple test example uses two predefined blocks, expect: (line 3) and where: (line 5). The where: block is used to define a data table that maps to the expectation of the Math.max function defined in line 4. Line 2 demonstrates how a custom name can be defined for a test.

An entire project containing JUnit and Spock code samples can be found on GitHub.

As far back as 2008 InfoQ reported on some speculation of JUnit’s demise. Eight years later JUnit 5 is alive and well and milestone 1 is in development. Test well and prosper!

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