EqualityComparisonAssertion

Issue ID EqualityComparisonAssertion · Severity Warning · Category Usability · Default on

Flags assertThat(a == b) (and a != b) where assertk's isEqualTo / isNotEqualTo should be used.

Why

Wrapping the comparison in assertThat and then asserting on the resulting Boolean produces a useless failure message ("expected true, got false"). isEqualTo shows both sides of the comparison and uses assertk's diffing for collections and data classes (see also isDataClassEqualTo).

Example

FlaggedPreferred

import assertk.assertThat
import assertk.assertions.isTrue

fun namesMatch() {
    val a = "Ada"
    val b = "Ada"
    assertThat(a == b).isTrue()
}

import assertk.assertThat
import assertk.assertions.isEqualTo

fun namesMatch() {
    val a = "Ada"
    val b = "Ada"
    assertThat(a).isEqualTo(b)
}

Quick fix

Yes — the IDE picks the non-literal side as the subject, the literal/string-template side as the expected value, and rewrites isTrue()/isFalse() to isEqualTo/isNotEqualTo.

Pattern	Becomes
assertThat(a == b).isTrue()	assertThat(a).isEqualTo(b)
assertThat(a == b).isFalse()	assertThat(a).isNotEqualTo(b)
assertThat(a != b).isTrue()	assertThat(a).isNotEqualTo(b)
assertThat(a != b).isFalse()	assertThat(a).isEqualTo(b)

Source

BooleanExpressionSubjectDetector.kt