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CollectionSizeAssertion

Issue ID CollectionSizeAssertion · Severity Warning · Category Productivity · Default on

Flags assertThat(collection.size).isEqualTo(n) where assertk's hasSize should be used instead.

Why

hasSize is purpose-built for collection length assertions. The failure message names the collection rather than just reporting a mismatched integer, and the call reads more naturally. The detector specifically looks for .size reads on subtypes of java.util.Collection followed by an isEqualTo assertion from assertk.assertions.AnyKt.

Example

import assertk.assertThat
import assertk.assertions.isEqualTo

fun listSize() {
    val list: List<Int> = listOf(10, 100, 1_000)
    assertThat(list.size).isEqualTo(3)
}

import assertk.assertThat
import assertk.assertions.hasSize

fun listSize() {
    val list: List<Int> = listOf(10, 100, 1_000)
    assertThat(list).hasSize(3)
}

The detector also catches indirect reads:

data class Holder(val list: List<Int>)

assertThat(holder.list.size).isEqualTo(3) // flagged

Quick fix

Yes — the IDE rewrites the subject from collection.size to collection, replaces isEqualTo(n) with hasSize(n), and adds the assertk.assertions.hasSize import.

Source

CollectionAssertionDetector.kt