Add auto-config for WebFlux OAuth2 Login

Closes gh-13142

spring-boot-samples/spring-boot-sample-reactive-oauth2-client/src/test/java/sample/oauth2/client/SampleReactiveOAuth2ClientApplicationTests.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2012-2018 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 sample.oauth2.client;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.reactive.server.WebTestClient;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT, properties = {
+		"APP-CLIENT-ID=my-client-id", "APP-CLIENT-SECRET=my-client-secret" })
+public class SampleReactiveOAuth2ClientApplicationTests {
+
+	@Autowired
+	private WebTestClient webTestClient;
+
+	@Test
+	public void everythingShouldRedirectToLogin() {
+		this.webTestClient.get().uri("/").exchange()
+			.expectStatus().isFound()
+			.expectHeader().valueEquals("Location", "/login");
+	}
+
+	@Test
+	public void loginShouldHaveBothOAuthClientsToChooseFrom() {
+		byte[] body = this.webTestClient.get().uri("/login").exchange()
+				.expectStatus().isOk()
+				.returnResult(String.class).getResponseBodyContent();
+		String bodyString = new String(body);
+		assertThat(bodyString).contains("/oauth2/authorization/github-client-1");
+		assertThat(bodyString).contains("/oauth2/authorization/github-client-2");
+	}
+
+}