// Use when writing or refactoring Kotlin tests that need assertions, including JUnit tests, Wow/SagaSpec tests, JDK types, nullable values, collections, maps, time values, futures, predicates, custom data classes, or exception assertions with assertThrownBy.
| name | fluent-assert |
| description | Use when writing or refactoring Kotlin tests that need assertions, including JUnit tests, Wow/SagaSpec tests, JDK types, nullable values, collections, maps, time values, futures, predicates, custom data classes, or exception assertions with assertThrownBy. |
Use FluentAssert for Kotlin assertions in this repository and in downstream Kotlin test examples. Prefer the Kotlin extension style over direct AssertJ calls.
import me.ahoo.test.asserts.assert
actual.assert().isEqualTo(expected)
Avoid assertThat(actual) in ordinary test code. FluentAssert keeps nullable receivers natural:
val name: String? = null
name.assert().isNull()
| Need | Pattern |
|---|---|
| Primitive/string/object | value.assert().isEqualTo(expected) |
| Collection/list/map | items.assert().hasSize(2).contains("a") |
| Nullable value | value.assert().isNull() or value.assert().isNotNull() |
| Exception lambda | assertThrownBy<IllegalArgumentException> { call() }.hasMessage("bad") |
| Existing exception | throwable.assert().hasMessageContaining("bad") |
| Time month checks | date.assert().hasMonth(Month.APRIL) |
| Future success/failure | future.assert().isCompletedWithValue(value) / .isCompletedExceptionally() |
| Recursive comparison | actual.assert().usingRecursiveComparison().isEqualTo(expected) |
For exception lambdas, also import:
import me.ahoo.test.asserts.assertThrownBy
For month assertions, import java.time.Month; AssertJ expects Month, not an integer.
Use FluentAssert inside expectation blocks too:
expectCommandBody<UpdateDemo> {
data.assert().isNotNull().isEqualTo("updated")
}
For types implementing AssertJ's AssertProvider<A>, .assert() returns the provider's custom assertion type:
provider.assert().isPositive()
Only use direct assertThat when implementing the provider's assertThat() method or when a project explicitly requires raw AssertJ.
.assert() after assertThrownBy; it already returns ThrowableAssert<T>.Optional.of("x").assert().isPresent().isEmpty().OffsetDateTimeAssert.hasOffset(...).hasMonth(4) for LocalDate or YearMonth; use hasMonth(Month.APRIL).assertThat(value).usingRecursiveComparison(); keep chaining from value.assert().references/FULL-API.md when you need supported type coverage, installation snippets, or a fuller example.evals/evals.json as the regression prompt set when changing this skill.