End of Line blog

Thoughts on software development, by Adam Ruka

Specnaz 1.5 released!

When I first released Specnaz, my testing library for Java, Kotlin and Groovy, back in 2016, it leveraged JUnit 4 as its execution engine. It made perfect sense: you really don’t want to waste time re-writing all of that boring-yet-necessary infrastructure (test runners, result reporters, build tool plugins, IDE plugins, etc.), and piggy-backing on existing solutions lowers the barrier for adoption of a new tool like Specnaz considerably.

JUnit 4 was the obvious choice; it’s to this day the most popular Java testing framework, and its Runner API makes implementing custom testing solutions a breeze, even ones who look so radically different from the “standard” JUnit tests like Specnaz ones do.

However, even since the beginning, I structured the project in a way that clearly separated the core logic of executing a Specnaz spec from the JUnit 4 integration code, anticipating that JUnit 4 might not always be the only supported execution engine. This paid dividends last year, when, by popular demand, I was able to add support for running Specnaz specs with TestNG.

While JUnit 4 was the obvious choice back in 2016, today that same choice would be anything but obvious. JUnit 4 is effectively abandonware, having had its last stable release in 2014. Its development team is completely focused on its successor, JUnit 5, which, after spending 2 years in beta, finally had a General Availability release in September of 2017.

Since then, the momentum has visibly shifted to JUnit 5 as the future, and JUnit 4 being relegated pretty much exclusively to legacy projects. With this momentum shift, it was important that Specnaz follow suit, as I don’t want the project to be seen as only working with old and crufty technologies. So, with the release of version 1.5, Specnaz now supports JUnit 5 as the third test execution engine.

JUnit 5 with Java

To use the JUnit 5 support in Java, you need to depend on the new module specnaz-junit-platform instead of the JUnit 4 specnaz-junit one. In your spec class, you do the usual thing: implement the Specnaz interface, and then the call the describes method in the public, no-argument constructor of the class. The only JUnit 5-specific thing you need to do is annotate the class with the Testable annotation from the org.junit.platform.commons.annotation package in the junit-platform module. Here’s an example of the StackSpec from the main Specnaz ReadMe using JUnit 5:

import org.junit.platform.commons.annotation.Testable;
import org.specnaz.Specnaz;
import java.util.Stack;
import static org.assertj.core.api.Assertions.assertThat;

public class StackSpec implements Specnaz {{
    describes("A Stack", it -> {
        Stack<Integer> stack = new Stack<>();

        it.endsEach(() -> {

        it.should("be empty when first created", () -> {

        it.describes("with 10 and 20 pushed on it", () -> {
            it.beginsEach(() -> {

            it.should("have size equal to 2", () -> {

            it.should("have 20 as the top element", () -> {

Parametrized tests are pretty much identical; the only difference is implementing the SpecnazParams interface instead of Specnaz. Everything else, including the @Testable annotation, remain the same.

JUnit 5 in Kotlin

The JUnit 5 support in Kotlin is very similar to the Java one. There is the new specnaz-kotlin-junit-platform module that you need to depend on, and your spec class has to implement the SpecnazKotlin interface instead of Specnaz, like always when writing specs in Kotlin. Other than that, things are pretty much identical to the Java experience: you annotate your class with the @Testable, and call the describes method in the constructor, as usual:

import org.junit.platform.commons.annotation.Testable
import org.specnaz.kotlin.SpecnazKotlin
import java.util.Stack
import org.assertj.core.api.Assertions.assertThat

class StackSpec : SpecnazKotlin {
    init {
        describes("A Stack") {
            var stack = Stack<Int>()

            it.endsEach {
                stack = Stack()

            it.should("be empty when first created") {

            it.describes("with 10 and 20 pushed on it") {
                it.beginsEach {

                it.should("have size equal to 2") {

                it.should("have 20 as the top element") {

In addition, there is a SpecnazKotlinJUnitPlatform class, which is analogous to the SpecnazKotlinJUnit class from the specnaz-junit module and the SpecnazKotlinTestNG class from the specnaz-testng module. It implements the SpecnazKotlin interface, is already annotated with the @Testable annotation, and calls the describes method in its primary constructor – which means you can save a little boilerplate code, and some indentation, if your spec class does not need to extend a particular class. Here’s the same StackSpec class above, but using SpecnazKotlinJUnitPlatform:

import org.specnaz.kotlin.junit.platform.SpecnazKotlinJUnitPlatform
import java.util.Stack
import org.assertj.core.api.Assertions.assertThat

class StackKotlinSpec : SpecnazKotlinJUnitPlatform("A Stack", {
    var stack = Stack<Int>()

    // the spec body is the same as above...

Parametrized tests are very similar to their Java counterparts: you either implement the SpecnazKotlinParams interface and annotate your class with the @Testable annotation, or you extend the SpecnazKotlinParamsJUnitPlatform class from the org.specnaz.kotlin.params.junit.platform package.

Further information

For more details about the JUnit 5 support, check out the Specnaz reference documentation on the topic. There is also an examples directory in the main distribution that contains some simple working tests with JUnit 5.