Add Undertow WebSocket sample application

See gh-2028

spring-boot-samples/spring-boot-sample-websocket-undertow/src/test/java/samples/websocket/snake/SnakeTimerTests.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2012-2013 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 samples.websocket.snake;
+
+import java.io.IOException;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+import static org.mockito.BDDMockito.willThrow;
+import static org.mockito.Matchers.anyString;
+import static org.mockito.Mockito.mock;
+
+public class SnakeTimerTests {
+
+	@Test
+	public void removeDysfunctionalSnakes() throws Exception {
+		Snake snake = mock(Snake.class);
+		willThrow(new IOException()).given(snake).sendMessage(anyString());
+		SnakeTimer.addSnake(snake);
+
+		SnakeTimer.broadcast("");
+		assertThat(SnakeTimer.getSnakes().size(), is(0));
+	}
+}