[FIXED] How to write junit test for object class in kotlin/android?

Issue

Maybe this is very basic question but could not find anything online.

I have created a object class in kotlin contains few methods. I am calling those from ViewModel and I have written junit test case for ViewModel where object class instance is mocked, fine so far.

Now, I want to write junit for my object class separately as well even though from ViewModel verify() calls are working fine.

Some code snippet from my project

object InfoHelper {

    fun method(param: Xyz): Boolean {
        return when(param) {
            Result.OK -> true
            else -> false
        }
    }

}

Solution

Unit testing Kotlin object classes:

The same as testing a Java static method and class. The class under test and it's methods can be tested directly without initialisation.

Using your class as a loose example..

object InfoHelper {
    fun method(param: String): Boolean {
        return when(param) {
            "my string" -> true
            else -> false
        }
    }
}

The test:

import org.junit.Assert.assertFalse
import org.junit.Assert.assertTrue
import org.junit.Test

class InfoHelperTest {
    @Test
    fun `some test returns true`() {
        assertTrue(InfoHelper.method("my string"))
    }

    @Test
    fun `some test returns false`() {
        assertFalse(InfoHelper.method("not my string"))
    }
}

Answered By - JakeB
Answer Checked By - David Marino (JavaFixing Volunteer)