Add unit tests for CoroutinesUtils

Closes gh-29968

Author: sdeleuze

spring-core/spring-core.gradle

@@ -86,6 +86,7 @@ dependencies {
 	testImplementation("com.squareup.okhttp3:mockwebserver")
 	testImplementation("org.jetbrains.kotlinx:kotlinx-serialization-json")
 	testImplementation("com.fasterxml.jackson.core:jackson-databind")
+	testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-reactor")
 	testFixturesImplementation("com.google.code.findbugs:jsr305")
 	testFixturesImplementation("org.junit.platform:junit-platform-launcher")
 	testFixturesImplementation("org.junit.jupiter:junit-jupiter-api")

spring-core/src/test/kotlin/org/springframework/core/KotlinCoroutinesUtilsTests.kt

@@ -0,0 +1,143 @@
+/*
+ * Copyright 2002-2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core
+
+import kotlinx.coroutines.*
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.reactor.awaitSingle
+import org.assertj.core.api.Assertions
+import org.junit.jupiter.api.Test
+import reactor.core.publisher.Flux
+import reactor.core.publisher.Mono
+import reactor.test.StepVerifier
+import kotlin.coroutines.Continuation
+import kotlin.coroutines.coroutineContext
+
+class KotlinCoroutinesUtilsTests {
+
+	@Test
+	fun deferredToMono() {
+		runBlocking {
+			val deferred: Deferred<String> = async(Dispatchers.IO) {
+				delay(10)
+				"foo"
+			}
+			val mono = CoroutinesUtils.deferredToMono(deferred)
+			StepVerifier.create(mono)
+				.expectNext("foo")
+				.expectComplete()
+				.verify()
+		}
+	}
+
+	@Test
+	fun monoToDeferred() {
+		runBlocking {
+			val mono = Mono.just("foo")
+			val deferred = CoroutinesUtils.monoToDeferred(mono)
+			Assertions.assertThat(deferred.await()).isEqualTo("foo")
+		}
+	}
+
+	@Test
+	fun invokeSuspendingFunctionWithNullContinuationParameter() {
+		val method = KotlinCoroutinesUtilsTests::class.java.getDeclaredMethod("suspendingFunction", String::class.java, Continuation::class.java)
+		val publisher = CoroutinesUtils.invokeSuspendingFunction(method, this, "foo", null)
+		Assertions.assertThat(publisher).isInstanceOf(Mono::class.java)
+		StepVerifier.create(publisher)
+			.expectNext("foo")
+			.expectComplete()
+			.verify()
+	}
+
+	@Test
+	fun invokeSuspendingFunctionWithoutContinuationParameter() {
+		val method = KotlinCoroutinesUtilsTests::class.java.getDeclaredMethod("suspendingFunction", String::class.java, Continuation::class.java)
+		val publisher = CoroutinesUtils.invokeSuspendingFunction(method, this, "foo")
+		Assertions.assertThat(publisher).isInstanceOf(Mono::class.java)
+		StepVerifier.create(publisher)
+			.expectNext("foo")
+			.expectComplete()
+			.verify()
+	}
+
+	@Test
+	fun invokeNonSuspendingFunction() {
+		val method = KotlinCoroutinesUtilsTests::class.java.getDeclaredMethod("nonSuspendingFunction", String::class.java)
+		Assertions.assertThatIllegalArgumentException().isThrownBy { CoroutinesUtils.invokeSuspendingFunction(method, this, "foo") }
+	}
+
+	@Test
+	fun invokeSuspendingFunctionWithFlow() {
+		val method = KotlinCoroutinesUtilsTests::class.java.getDeclaredMethod("suspendingFunctionWithFlow", Continuation::class.java)
+		val publisher = CoroutinesUtils.invokeSuspendingFunction(method, this)
+		Assertions.assertThat(publisher).isInstanceOf(Flux::class.java)
+		StepVerifier.create(publisher)
+			.expectNext("foo")
+			.expectNext("bar")
+			.expectComplete()
+			.verify()
+	}
+
+	@Test
+	fun invokeSuspendingFunctionWithNullContinuationParameterAndContext() {
+		val method = KotlinCoroutinesUtilsTests::class.java.getDeclaredMethod("suspendingFunctionWithContext", String::class.java, Continuation::class.java)
+		val context = CoroutineName("name")
+		val mono = CoroutinesUtils.invokeSuspendingFunction(context, method, this, "foo", null) as Mono
+		runBlocking {
+			Assertions.assertThat(mono.awaitSingle()).isEqualTo("foo")
+		}
+	}
+
+	@Test
+	fun invokeSuspendingFunctionWithoutContinuationParameterAndContext() {
+		val method = KotlinCoroutinesUtilsTests::class.java.getDeclaredMethod("suspendingFunctionWithContext", String::class.java, Continuation::class.java)
+		val context = CoroutineName("name")
+		val mono = CoroutinesUtils.invokeSuspendingFunction(context, method, this, "foo") as Mono
+		runBlocking {
+			Assertions.assertThat(mono.awaitSingle()).isEqualTo("foo")
+		}
+	}
+
+	@Test
+	fun invokeNonSuspendingFunctionWithContext() {
+		val method = KotlinCoroutinesUtilsTests::class.java.getDeclaredMethod("nonSuspendingFunction", String::class.java)
+		Assertions.assertThatIllegalArgumentException().isThrownBy { CoroutinesUtils.invokeSuspendingFunction(method, this, "foo") }
+	}
+
+	suspend fun suspendingFunction(value: String): String {
+		delay(10)
+		return value
+	}
+
+	suspend fun suspendingFunctionWithFlow(): Flow<String> {
+		delay(10)
+		return flowOf("foo", "bar")
+	}
+
+	fun nonSuspendingFunction(value: String): String {
+		return value
+	}
+
+	suspend fun suspendingFunctionWithContext(value: String): String {
+		delay(10)
+		Assertions.assertThat(coroutineContext[CoroutineName]?.name).isEqualTo("name")
+		return value
+	}
+
+}