Fix NPE when local leader is null (#297)

spring-cloud-kubernetes-leader/src/main/java/org/springframework/cloud/kubernetes/leader/LeadershipController.java

@@ -68,7 +68,7 @@ public class LeadershipController {
 	}
 
 	public Optional<Leader> getLocalLeader() {
-		return Optional.of(localLeader);
+		return Optional.ofNullable(localLeader);
 	}
 
 	public synchronized void update() {

spring-cloud-kubernetes-leader/src/test/java/org/springframework/cloud/kubernetes/leader/LeadershipControllerTest.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2013-2018 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 org.springframework.cloud.kubernetes.leader;
+
+import io.fabric8.kubernetes.client.KubernetesClient;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+import org.springframework.integration.leader.Candidate;
+import org.springframework.integration.leader.event.LeaderEventPublisher;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Gytis Trikleris
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class LeadershipControllerTest {
+
+	@Mock
+	private Candidate mockCandidate;
+
+	@Mock
+	private LeaderProperties mockLeaderProperties;
+
+	@Mock
+	private LeaderEventPublisher mockLeaderEventPublisher;
+
+	@Mock
+	private KubernetesClient mockKubernetesClient;
+
+	private LeadershipController leadershipController;
+
+	@Before
+	public void before() {
+		leadershipController = new LeadershipController(mockCandidate, mockLeaderProperties, mockLeaderEventPublisher,
+			mockKubernetesClient);
+	}
+
+	@Test
+	public void shouldGetEmptyLocalLeader() {
+		assertThat(leadershipController.getLocalLeader().isPresent()).isFalse();
+	}
+
+}