Add Kotlin extensions for WebTestClient API

Issue: SPR-15622

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
+
+}