Change Arb.filterIsInstance() signature to use single type parameter (#…

…3943)
kotest · Mar 20, 2024 · eff1ab0 · eff1ab0
1 parent 0315867
commit eff1ab0
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/kotest-property/src/commonMain/kotlin/io/kotest/property/arbitrary/filter.kt b/kotest-property/src/commonMain/kotlin/io/kotest/property/arbitrary/filter.kt
@@ -39,4 +39,4 @@ fun <A> Arb<A>.filterNot(f: (A) -> Boolean): Arb<A> = filter { !f(it) }
  * a particular subtype.
  */
 @Suppress("UNCHECKED_CAST")
-inline fun <A, reified B : A> Arb<A>.filterIsInstance(): Arb<B> = filter { it is B }.map { it as B }
+inline fun <reified B> Arb<*>.filterIsInstance(): Arb<B> = filter { it is B } as Arb<B>
diff --git a/kotest-property/src/jvmTest/kotlin/com/sksamuel/kotest/property/arbitrary/FilterTest.kt b/kotest-property/src/jvmTest/kotlin/com/sksamuel/kotest/property/arbitrary/FilterTest.kt
@@ -6,12 +6,15 @@ import io.kotest.core.spec.style.FunSpec
 import io.kotest.inspectors.forAll
 import io.kotest.matchers.collections.shouldContainExactly
 import io.kotest.matchers.collections.shouldNotBeIn
+import io.kotest.matchers.should
 import io.kotest.matchers.shouldBe
+import io.kotest.matchers.types.beInstanceOf
 import io.kotest.property.Arb
 import io.kotest.property.EdgeConfig
 import io.kotest.property.RandomSource
 import io.kotest.property.Sample
 import io.kotest.property.arbitrary.filter
+import io.kotest.property.arbitrary.filterIsInstance
 import io.kotest.property.arbitrary.int
 import io.kotest.property.arbitrary.map
 import io.kotest.property.arbitrary.of
@@ -68,4 +71,11 @@ class FilterTest : FunSpec({
       val result = shouldNotThrowAny { arb.single(RandomSource.seeded(1234L)) }
       result shouldBe 0
    }
+
+   test("Arb.filterIsInstance should only keep instances of the given type") {
+      val arb: Arb<Any> = Arb.of(1, "2", 3.0, "4", 5)
+      val filtered = arb.filterIsInstance<String>()
+      val result = filtered.samples().take(100).map { it.value }
+      result.forAll { it should beInstanceOf(String::class) }
+   }
 })