Add Kotlin extensions for WebTestClient API

Issue: SPR-15622

build.gradle

@@ -1039,6 +1039,7 @@ project("spring-test") {
 		optional("org.reactivestreams:reactive-streams")
 		optional("io.projectreactor:reactor-core")
 		optional("io.projectreactor:reactor-test")
+		optional("org.jetbrains.kotlin:kotlin-stdlib:${kotlinVersion}")
 		testCompile(project(":spring-context-support"))
 		testCompile(project(":spring-oxm"))
 		testCompile("javax.mail:javax.mail-api:${javamailVersion}")

spring-test/src/main/java/org/springframework/test/web/reactive/server/WebTestClient.java

@@ -536,7 +536,7 @@ public interface WebTestClient {
 		 */
 		<B> BodySpec<B, ?> expectBody(ParameterizedTypeReference<B> bodyType);
 
-			/**
+		/**
 		 * Declare expectations on the response body decoded to {@code List<E>}.
 		 * @param elementType the expected List element type
 		 */

spring-test/src/main/kotlin/org/springframework/test/web/reactive/server/WebTestClientExtensions.kt

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2002-2017 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
+ *
+ *      http://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.test.web.reactive.server
+
+import org.reactivestreams.Publisher
+import kotlin.reflect.KClass
+
+/**
+ * Extension for [WebTestClient.RequestBodySpec.body] providing a variant without explicit class
+ * parameter thanks to Kotlin reified type parameters.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+inline fun <reified T : Any, S : Publisher<T>> WebTestClient.RequestBodySpec.body(publisher: S): WebTestClient.RequestHeadersSpec<*>
+		= body(publisher, T::class.java)
+
+/**
+ * Extension for [WebTestClient.ResponseSpec.expectBody] providing a [KClass] based variant.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+fun <B : Any> WebTestClient.ResponseSpec.expectBody(type: KClass<B>): WebTestClient.BodySpec<B, *> =
+		expectBody(type.java)
+
+/**
+ * Extension for [WebTestClient.ResponseSpec.expectBody] providing a `expectBody<Foo>()` variant.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+inline fun <reified B : Any> WebTestClient.ResponseSpec.expectBody(): WebTestClient.BodySpec<B, *> =
+		expectBody(B::class.java)
+
+/**
+ * Extension for [WebTestClient.ResponseSpec.expectBodyList] providing a [KClass] based variant.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+fun <E : Any> WebTestClient.ResponseSpec.expectBodyList(type: KClass<E>): WebTestClient.ListBodySpec<E> =
+		expectBodyList(type.java)
+
+/**
+ * Extension for [WebTestClient.ResponseSpec.expectBodyList] providing a `expectBodyList<Foo>()` variant.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+inline fun <reified E : Any> WebTestClient.ResponseSpec.expectBodyList(): WebTestClient.ListBodySpec<E> =
+		expectBodyList(E::class.java)
+
+/**
+ * Extension for [WebTestClient.ResponseSpec.returnResult] providing a [KClass] based variant.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+fun <T : Any> WebTestClient.ResponseSpec.returnResult(type: KClass<T>): FluxExchangeResult<T> =
+		returnResult(type.java)
+
+/**
+ * Extension for [WebTestClient.ResponseSpec.returnResult] providing a `returnResult<Foo>()` variant.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+inline fun <reified T : Any> WebTestClient.ResponseSpec.returnResult(): FluxExchangeResult<T> =
+		returnResult(T::class.java)

spring-test/src/test/kotlin/org/springframework/test/web/reactive/server/WebTestClientExtensionsTests.kt

@@ -0,0 +1,74 @@
+package org.springframework.test.web.reactive.server
+
+import com.nhaarman.mockito_kotlin.mock
+import com.nhaarman.mockito_kotlin.times
+import com.nhaarman.mockito_kotlin.verify
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.Answers
+import org.mockito.Mock
+import org.mockito.junit.MockitoJUnitRunner
+import org.reactivestreams.Publisher
+
+
+/**
+ * Mock object based tests for [WebTestClient] Kotlin extensions
+ *
+ * @author Sebastien Deleuze
+ */
+@RunWith(MockitoJUnitRunner::class)
+class WebTestClientExtensionsTests {
+
+	@Mock(answer = Answers.RETURNS_MOCKS)
+	lateinit var requestBodySpec: WebTestClient.RequestBodySpec
+
+	@Mock(answer = Answers.RETURNS_MOCKS)
+	lateinit var responseSpec: WebTestClient.ResponseSpec
+
+
+	@Test
+	fun `RequestBodySpec#body with Publisher and reified type parameters`() {
+		val body = mock<Publisher<Foo>>()
+		requestBodySpec.body(body)
+		verify(requestBodySpec, times(1)).body(body, Foo::class.java)
+	}
+
+	@Test
+	fun `ResponseSpec#expectBody with KClass`() {
+		responseSpec.expectBody(Foo::class)
+		verify(responseSpec, times(1)).expectBody(Foo::class.java)
+	}
+
+	@Test
+	fun `ResponseSpec#expectBody with reified type parameters`() {
+		responseSpec.expectBody<Foo>()
+		verify(responseSpec, times(1)).expectBody(Foo::class.java)
+	}
+
+	@Test
+	fun `ResponseSpec#expectBodyList with KClass`() {
+		responseSpec.expectBodyList(Foo::class)
+		verify(responseSpec, times(1)).expectBodyList(Foo::class.java)
+	}
+
+	@Test
+	fun `ResponseSpec#expectBodyList with reified type parameters`() {
+		responseSpec.expectBodyList<Foo>()
+		verify(responseSpec, times(1)).expectBodyList(Foo::class.java)
+	}
+
+	@Test
+	fun `ResponseSpec#returnResult with KClass`() {
+		responseSpec.returnResult(Foo::class)
+		verify(responseSpec, times(1)).returnResult(Foo::class.java)
+	}
+
+	@Test
+	fun `ResponseSpec#returnResult with reified type parameters`() {
+		responseSpec.returnResult<Foo>()
+		verify(responseSpec, times(1)).returnResult(Foo::class.java)
+	}
+
+	class Foo
+
+}