Skip to content

MapValueAssertion

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

Flags assertThat(map[key]), assertThat(map.get(key)), assertThat(map.getOrElse(...)), and assertThat(map.getValue(key)) — all of which read a value out of the map before the assertion subject is created. Use Assert<Map<K, V>>.key(key): Assert<V> instead.

Why

Pulling the value out of the map first hides the failure mode: if the key is absent, Map.get returns null (and you'd be asserting on null), and Map.getValue throws a NoSuchElementException (which looks like a crash rather than a test failure). key(k) asserts that the key is present and transforms the subject to Assert<V> so you can chain further assertions on the value.

Recognised map accessors: get, getValue, getOrElse, getOrDefault, plus the [] operator.

Example

import assertk.assertThat
import assertk.assertions.isNotNull

fun lookup() {
    val map: Map<String, String?> = mapOf("9A3E6FAC" to "John")
    assertThat(map["9A3E6FAC"]).isNotNull()
}

import assertk.assertThat
import assertk.assertions.key
import assertk.assertions.isNotNull

fun lookup() {
    val map: Map<String, String?> = mapOf("9A3E6FAC" to "John")
    assertThat(map).key("9A3E6FAC").isNotNull()
}

Quick fix

Yes — the IDE rewrites assertThat(map[k]) to assertThat(map).key(k) and adds assertk.assertions.key. String literals are quoted correctly when the IR strips the surrounding quotes.

Source

MapAssertionDetector.kt