[ONOS-4438] Add codecs for mastership REST API

Add codecs for RoleInfo, MastershipTerm and MastershipRole.

Change-Id: I1135c7fc0ed591446d6268229b54fda70391fdb9
diff --git a/core/common/src/test/java/org/onosproject/codec/impl/MastershipRoleCodecTest.java b/core/common/src/test/java/org/onosproject/codec/impl/MastershipRoleCodecTest.java
new file mode 100644
index 0000000..fda4de6
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+++ b/core/common/src/test/java/org/onosproject/codec/impl/MastershipRoleCodecTest.java
@@ -0,0 +1,124 @@
+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * 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.onosproject.codec.impl;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import org.hamcrest.Description;
+import org.hamcrest.TypeSafeDiagnosingMatcher;
+import org.junit.Before;
+import org.junit.Test;
+import org.onosproject.codec.JsonCodec;
+import org.onosproject.net.MastershipRole;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.notNullValue;
+import static org.onosproject.net.MastershipRole.MASTER;
+
+/**
+ * Unit tests for mastership role codec.
+ */
+public final class MastershipRoleCodecTest {
+
+    MockCodecContext context;
+    JsonCodec<MastershipRole> mastershipRoleCodec;
+
+    /**
+     * Sets up for each test. Creates a context and fetches the mastership role
+     * codec.
+     */
+    @Before
+    public void setUp() {
+        context = new MockCodecContext();
+        mastershipRoleCodec = context.codec(MastershipRole.class);
+        assertThat(mastershipRoleCodec, notNullValue());
+    }
+
+    /**
+     * Tests encoding of a mastership role object.
+     */
+    @Test
+    public void testMastershipRoleEncode() {
+        MastershipRole mastershipRole = MASTER;
+        ObjectNode mastershipRoleJson = mastershipRoleCodec.encode(mastershipRole, context);
+        assertThat(mastershipRoleJson, MastershipRoleJsonMatcher.matchesMastershipRole(mastershipRole));
+    }
+
+    /**
+     * Tests decoding of mastership role JSON object.
+     */
+    @Test
+    public void testMastershipRoleDecode() throws IOException {
+        MastershipRole mastershipRole = getMastershipRole("MastershipRole.json");
+
+        assertThat(mastershipRole, is(MASTER));
+    }
+
+    /**
+     * Hamcrest matcher for mastership role.
+     */
+    private static final class MastershipRoleJsonMatcher extends TypeSafeDiagnosingMatcher<JsonNode> {
+
+        private final MastershipRole mastershipRole;
+
+        private MastershipRoleJsonMatcher(MastershipRole mastershipRole) {
+            this.mastershipRole = mastershipRole;
+        }
+
+        @Override
+        protected boolean matchesSafely(JsonNode jsonNode, Description description) {
+
+            // check mastership role
+            String jsonRole = jsonNode.get("role").asText();
+            String role = mastershipRole.name();
+            if (!jsonRole.equals(role)) {
+                description.appendText("mastership role was " + jsonRole);
+                return false;
+            }
+
+            return true;
+        }
+
+        @Override
+        public void describeTo(Description description) {
+            description.appendText(mastershipRole.toString());
+        }
+
+        static MastershipRoleJsonMatcher matchesMastershipRole(MastershipRole mastershipRole) {
+            return new MastershipRoleJsonMatcher(mastershipRole);
+        }
+    }
+
+    /**
+     * Reads in a mastership role from the given resource and decodes it.
+     *
+     * @param resourceName resource to use to read the JSON for the rule
+     * @return decoded mastership term object
+     * @throws IOException if processing the resource fails
+     */
+    private MastershipRole getMastershipRole(String resourceName) throws IOException {
+        InputStream jsonStream = MastershipRoleCodecTest.class.getResourceAsStream(resourceName);
+        JsonNode json = context.mapper().readTree(jsonStream);
+        assertThat(json, notNullValue());
+        MastershipRole mastershipRole = mastershipRoleCodec.decode((ObjectNode) json, context);
+        assertThat(mastershipRole, notNullValue());
+        return mastershipRole;
+    }
+}