TestFrameworkAssertionUse¶

Issue ID TestFrameworkAssertionUse · Severity Warning · Category Correctness · Default on

Flags assertion calls into the bundled JUnit 4, JUnit 5, or kotlin.test assertion APIs when assertk is on the classpath.

Why¶

Test frameworks ship their own assertions for convenience, but their failure messages and discoverability are weaker than a fluent assertion library's. Standardising on assertk gives you consistent output and access to richer combinators (prop, index, key, …).

The detector recognises members of:

org.junit.Assert (JUnit 4)
org.junit.jupiter.api.Assertions (JUnit 5)
kotlin.test.AssertionsKt / kotlin.test.AssertionsKt__AssertionsKt

Example¶

FlaggedPreferred

import org.junit.Assert.assertEquals

class TestingTesting {
    fun testingTest() {
        val first = File()
        val second = File()
        assertEquals(first, second)
    }
}

import assertk.assertThat
import assertk.assertions.isEqualTo

class TestingTesting {
    fun testingTest() {
        val first = File()
        val second = File()
        assertThat(first).isEqualTo(second)
    }
}

Quick fix¶

Yes for JUnit 4 and kotlin.test assertions. The fix recognises:

Original	Replacement
`assertEquals(expected, actual)`	`assertThat(actual).isEqualTo(expected)`
`assertNotEquals(expected, actual)`	`assertThat(actual).isNotEqualTo(expected)`
`assertTrue(actual)`	`assertThat(actual).isTrue()`
`assertFalse(actual)`	`assertThat(actual).isFalse()`
`assertNull(actual)`	`assertThat(actual).isNull()`
`assertNotNull(actual)`	`assertThat(actual).isNotNull()`
`assertSame(expected, actual)`	`assertThat(actual).isSameAs(expected)`
`assertNotSame(expected, actual)`	`assertThat(actual).isNotSameAs(expected)`
`assertArrayEquals(expected, actual)`	`assertThat(actual).containsOnly(*expected)`
`assertIs<T>(value)` (kotlin.test)	`assertThat(value).isInstanceOf<T>()`
`assertIsNot<T>(value)` (kotlin.test)	`assertThat(value).isNotInstanceOf<T>()`
`fail(message)`	`assertk.fail(message)`

If the original call carried a message argument, it is preserved as a trailing comment so context isn't lost when the rewrite produces a shorter form.

JUnit 5 calls are flagged but not auto-fixed — the parameter ordering and overloads vary enough that a mechanical rewrite isn't always safe.

Source¶

TestFrameworkAssertionDetector.kt