JUnit test in nested Kotlin class not found when running gradle test

Question

When I specify a test in a nested class in Kotlin as follows ...

import org.junit.jupiter.api.*

class ParentTest
{
    @Nested
    class NestedTest
    {
        @Test
        fun NotFoundTest() {}
    }

    @Test
    fun FoundTest() {}
}

... it is not recognized by JUnit when running tests using gradle. Only FoundTest is found and ran.

I am using JUnit 5.1 and Kotlin 1.2.30 and Gradle 4.6.

Steven Jeuris · Accepted Answer · 2018-03-10T17:31:37.873

35

Defining the nested class as an inner class resolves this issue.

class ParentTest
{
    @Nested
    inner class NestedTest
    {
        @Test
        fun InnerTestFound() {}
    }

    @Test
    fun FoundTest() {}
}

As Sam Brannen indicates, "by default, a nested class in Kotlin is similar to a static class in Java" and the JUnit documentation indicates:

Only non-static nested classes (i.e. inner classes) can serve as @Nested test classes.

Marking the class as inner in Kotlin compiles to a non-static Java class.

edited Mar 10 '18 at 17:31

answered Mar 08 '18 at 19:17

Steven Jeuris

18,274
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@Sevastyan And all your other tests get recognized as expected? What version are you using? – Steven Jeuris Oct 31 '18 at 13:09
4

`testImplementation 'org.junit.jupiter:junit-jupiter-api:5.3.1'` and `testImplementation 'org.junit.jupiter:junit-jupiter-engine:5.3.1'` with Kotlin `1.3.0` Nested classes are not recognized at all - tests in them don't appear in the list of tests. – Sevastyan Savanyuk Oct 31 '18 at 13:57
Are you _other_ (non-nested) tests recognized as expected? – Steven Jeuris Oct 31 '18 at 16:25
1

Yes, other top level tests are recognized. – Sevastyan Savanyuk Oct 31 '18 at 16:49
`Rebuild Project` might be needed after writing `inner` keyword – Jemshit Jun 29 '19 at 07:40
5

I had the same issue but @user949884 was right, I didn't have the correct import. I had import org.junit.Test instead of import org.junit.jupiter.api.Test. After changing the import the tests were found. – Laura Oct 25 '19 at 08:51
I did all those things (rebuild, import the correct `Test`, add `inner`) but still doesn't find the tests. – Rodrigo Ruiz Feb 07 '20 at 18:53

score 6 · Answer 2 · answered Mar 09 '18 at 07:54

6

From the documentation:

Only non-static nested classes (i.e. inner classes) can serve as @Nested test classes.

Thus, you need to make NestedTest an inner class.

answered Mar 09 '18 at 07:54

Marc Philipp

1,848
12
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1

I did read that, but be aware this is Java documentation. 'static' is not a thing in Kotlin and the reference to 'inner' class is not exactly the same as the 'inner' keyword for [inner classes in kotlin](https://kotlinlang.org/docs/reference/nested-classes.html). For example, does this mean by default Kotlin classes all compile to static classes? That said, reading this is why I tried specifying the class as (Kotlin) inner orginally, just not certain about the specifics. – Steven Jeuris Mar 09 '18 at 09:06
2

Yes, by default, a _nested_ class in Kotlin is similar to a `static` class in Java. – Sam Brannen Mar 10 '18 at 16:18
Nesting classes in Kotlin acts more like using namespaces - unless explicitly wanted, nothing becomes an inner class with a reference to the outer class. This is actually very good. – Zordid Mar 08 '22 at 12:29

JUnit test in nested Kotlin class not found when running gradle test

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