Added tests for other changes and issue and merge request specific changes (#362).

Author: gmessner

src/test/java/org/gitlab4j/api/TestGitLabApiEvents.java

@@ -5,7 +5,9 @@
 import static org.gitlab4j.api.JsonUtils.readTreeFromResource;
 import static org.gitlab4j.api.JsonUtils.unmarshalResource;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Mockito.mock;
@@ -23,7 +25,7 @@
 import org.gitlab4j.api.systemhooks.SystemHookManager;
 import org.gitlab4j.api.systemhooks.TeamMemberSystemHookEvent;
 import org.gitlab4j.api.utils.JacksonJson;
-import org.gitlab4j.api.webhook.BuildEvent;
+import org.gitlab4j.api.webhook.*;
 import org.gitlab4j.api.webhook.Event;
 import org.gitlab4j.api.webhook.IssueEvent;
 import org.gitlab4j.api.webhook.JobEvent;
@@ -65,17 +67,56 @@ public static void teardown() {
     @Test
     public void testIssueEvent() throws Exception {
 
-        Event issueEvent = unmarshalResource(IssueEvent.class, "issue-event.json");
+        IssueEvent issueEvent = unmarshalResource(IssueEvent.class, "issue-event.json");
         assertTrue(compareJson(issueEvent, "issue-event.json"));
+
+        ChangeContainer<Integer> idChange = issueEvent.getChanges().get("id");
+        assertNotNull(idChange);
+        assertEquals(123, (int)idChange.getPrevious());
+        assertEquals(456, (int)idChange.getCurrent());
+    }
+
+    @Test
+    public void testIssueChanges() throws Exception {
+
+        IssueEvent issueEvent = unmarshalResource(IssueEvent.class, "issue-event.json");
+        assertNotNull(issueEvent);
+
+        ChangeContainer<Integer> idChange = issueEvent.getChanges().get("id");
+        assertNotNull(idChange);
+        assertEquals(123, (int)idChange.getPrevious());
+        assertEquals(456, (int)idChange.getCurrent());
+
+        ChangeContainer<Boolean> confidentialChange = issueEvent.getChanges().getConfidential();
+        assertNotNull(confidentialChange);
+        assertFalse(confidentialChange.getPrevious());
+        assertTrue(confidentialChange.getCurrent());
     }
 
     @Test
     public void testMergeRequestEvent() throws Exception {
 
-        Event mergeRequestEvent = unmarshalResource(MergeRequestEvent.class, "merge-request-event.json");
+        MergeRequestEvent mergeRequestEvent = unmarshalResource(MergeRequestEvent.class, "merge-request-event.json");
         assertTrue(compareJson(mergeRequestEvent, "merge-request-event.json"));
     }
 
+    @Test
+    public void testMergeRequestEventChanges() throws Exception {
+
+        MergeRequestEvent mergeRequestEvent = unmarshalResource(MergeRequestEvent.class, "merge-request-event.json");
+        assertNotNull(mergeRequestEvent);
+
+        ChangeContainer<Integer> iidChange = mergeRequestEvent.getChanges().get("iid");
+        assertNotNull(iidChange);
+        assertEquals(12, (int)iidChange.getPrevious());
+        assertEquals(34, (int)iidChange.getCurrent());
+
+        ChangeContainer<String> mergeStatusChangeChange = mergeRequestEvent.getChanges().getMergeStatus();
+        assertNotNull(mergeStatusChangeChange);
+        assertNull(mergeStatusChangeChange.getPrevious());
+        assertEquals("unchecked", mergeStatusChangeChange.getCurrent());
+    }
+
     @Test
     public void testPipelineEvent() throws Exception {
         Event event = unmarshalResource(PipelineEvent.class, "pipeline-event.json");

src/test/resources/org/gitlab4j/api/issue-event.json

@@ -57,6 +57,10 @@
        "previous": "2020-06-01T08:00:00Z",
        "current": "2020-02-04T08:00:00Z"
     },
+    "confidential": {
+       "previous": false,
+       "current": true
+    },
     "updated_at": {
        "previous":"2019-04-12T01:10:28Z",
        "current":"2019-04-12T01:11:33Z"
@@ -65,13 +69,21 @@
        "previous": 2,
        "current": 6
     },
+    "id":{
+       "previous":123,
+       "current":456
+   	},
+    "iid":{
+       "previous":12,
+       "current":34
+    },
     "milestone_id": {
        "previous":0,
        "current":1
     },
     "confidential": {
-       "previous":true,
-       "current":false
+       "previous":false,
+       "current":true
     },
     "labels": {
       "previous": [{

src/test/resources/org/gitlab4j/api/merge-request-event.json

@@ -104,14 +104,31 @@
     "group_id": 41
   }],
   "changes": {
+    "author_id": {
+       "current":2
+    },
     "updated_at": {
-       "previous":"2019-04-12T01:10:28Z",
-       "current":"2019-04-12T01:11:33Z"
+       "current": "2013-12-03T17:23:34Z"
     },
     "updated_by_id": {
        "previous": 2,
        "current": 6
     },
+    "id":{
+       "previous":123,
+       "current":456
+   	},
+    "iid":{
+       "previous":12,
+       "current":34
+    },
+    "merge_status": {
+       "current": "unchecked"
+    },
+    "milestone_id": {
+       "previous":0,
+       "current":1
+    },
     "labels": {
       "previous": [{
         "id": 206,