Add tests for GET/PUT /config/server/preferences.diff endpoint

Change-Id: I1e729205833bd5d933ac4cce05b841044c232067

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/config/DiffPreferencesIT.java

@@ -0,0 +1,79 @@
+// Copyright (C) 2016 The Android Open Source Project
+//
+// 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 com.google.gerrit.acceptance.rest.config;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.gerrit.server.config.ConfigUtil.skipField;
+
+import com.google.gerrit.acceptance.AbstractDaemonTest;
+import com.google.gerrit.acceptance.RestResponse;
+import com.google.gerrit.extensions.client.DiffPreferencesInfo;
+
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+
+public class DiffPreferencesIT extends AbstractDaemonTest {
+
+  @Test
+  public void GetDiffPreferences() throws Exception {
+    DiffPreferencesInfo result = get();
+    assertPrefsEqual(result, DiffPreferencesInfo.defaults());
+  }
+
+  @Test
+  public void SetDiffPreferences() throws Exception {
+    int newLineLength = DiffPreferencesInfo.defaults().lineLength + 10;
+    DiffPreferencesInfo update = new DiffPreferencesInfo();
+    update.lineLength = newLineLength;
+    DiffPreferencesInfo result = put(update);
+    assertThat(result.lineLength).named("lineLength").isEqualTo(newLineLength);
+
+    result = get();
+    DiffPreferencesInfo expected = DiffPreferencesInfo.defaults();
+    expected.lineLength = newLineLength;
+    assertPrefsEqual(result, expected);
+  }
+
+  private DiffPreferencesInfo get() throws Exception {
+    RestResponse r = adminRestSession.get("/config/server/preferences.diff");
+    r.assertOK();
+    return newGson().fromJson(r.getReader(), DiffPreferencesInfo.class);
+  }
+
+  private DiffPreferencesInfo put(DiffPreferencesInfo input) throws Exception {
+    RestResponse r = adminRestSession.put(
+        "/config/server/preferences.diff", input);
+    r.assertOK();
+    return newGson().fromJson(r.getReader(), DiffPreferencesInfo.class);
+  }
+
+  private void assertPrefsEqual(DiffPreferencesInfo actual,
+      DiffPreferencesInfo expected) throws Exception {
+    for (Field field : actual.getClass().getDeclaredFields()) {
+      if (skipField(field)) {
+        continue;
+      }
+      Object actualField = field.get(actual);
+      Object expectedField = field.get(expected);
+      Class<?> type = field.getType();
+      if ((type == boolean.class || type == Boolean.class)
+          && actualField == null) {
+        continue;
+      }
+      assertThat(actualField).named(field.getName()).isEqualTo(expectedField);
+    }
+  }
+}