UnusedAssertkAssertion¶

Issue ID UnusedAssertkAssertion · Severity Error · Category Correctness · Default on

Flags an assertk.assertThat(...) call whose result is never followed by an assertion. Without an assertion the test cannot fail — the subject is created and immediately discarded.

Why¶

assertThat returns an Assert<T>. The actual check (isEqualTo, isNotNull, …) is a method on that subject. If nothing is invoked on the subject, no assertion runs, and the test silently passes regardless of the value.

The detector uses Lint's TargetMethodDataFlowAnalyzer to chase the subject through the enclosing method/lambda. It also has a deliberate carve-out for scope functions: assertThat(x).apply { isEqualTo(y) } and friends are considered used as long as the lambda body contains at least one call on an assertk.Assert receiver.

Example¶

FlaggedPreferred

import assertk.assertThat

class TestingTesting {
    fun testingTest() {
        val first = File()
        assertThat(first) // (1)
    }
}

No assertion is ever called on the subject — this test cannot fail.

import assertk.assertThat
import assertk.assertions.isEqualTo

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

        assertThat(first).isEqualTo(second)
    }
}

It also catches the lambda-arg case:

enum class Scenario(assertion: () -> Unit) {
    LambdaScenario(assertion = { assertThat("") }) // flagged
}

Quick fix¶

Available for several common cases — the detector recognises null comparisons, equality comparisons, and is-type checks passed as the assertThat argument and rewrites them into the proper assertion. For example:

assertThat(name == null)        // becomes
assertThat(name).isNull()

assertThat(value is String)     // becomes
assertThat(value).isInstanceOf<String>()

For other shapes, fix manually by chaining the appropriate assertion.

Source¶

UnusedAssertionDetector.kt