Add support for XEP-0428: Fallback Indication

Fixes SMACK-889

smack-experimental/src/test/java/org/jivesoftware/smackx/fallback_indication/FallbackIndicationTest.java

@@ -0,0 +1,42 @@
+/**
+ *
+ * Copyright 2020 Paul Schaub
+ *
+ * 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.jivesoftware.smackx.fallback_indication;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.jivesoftware.smack.packet.Message;
+import org.jivesoftware.smack.packet.MessageBuilder;
+
+import org.jivesoftware.smackx.fallback_indication.element.FallbackIndicationElement;
+
+import org.junit.jupiter.api.Test;
+
+public class FallbackIndicationTest {
+
+    @Test
+    public void testFallbackIndicationElementFromMessageTest() {
+        Message messageWithoutFallback = MessageBuilder.buildMessage()
+                        .build();
+        assertNull(FallbackIndicationElement.fromMessage(messageWithoutFallback));
+
+        Message messageWithFallback = MessageBuilder.buildMessage()
+                        .addExtension(new FallbackIndicationElement())
+                        .build();
+        assertNotNull(FallbackIndicationElement.fromMessage(messageWithFallback));
+    }
+}