Add database invariant checker []

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=119162082

javatests/com/google/domain/registry/testing/LogsSubject.java

@@ -0,0 +1,67 @@
+// Copyright 2016 The Domain Registry Authors. All Rights Reserved.
+//
+// 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.domain.registry.testing;
+
+import static com.google.common.truth.Truth.assertAbout;
+
+import com.google.common.testing.TestLogHandler;
+import com.google.common.truth.AbstractVerb.DelegatedVerb;
+import com.google.common.truth.FailureStrategy;
+import com.google.common.truth.Subject;
+import com.google.domain.registry.testing.TruthChainer.And;
+
+import java.util.logging.Handler;
+import java.util.logging.Level;
+import java.util.logging.LogRecord;
+
+/** Utility methods for asserting things about logging {@link Handler} instances. */
+public class LogsSubject extends Subject<LogsSubject, TestLogHandler> {
+
+  /** A factory for instances of this subject. */
+  private static class SubjectFactory
+      extends ReflectiveSubjectFactory<TestLogHandler, LogsSubject> {}
+
+  public LogsSubject(FailureStrategy strategy, TestLogHandler subject) {
+    super(strategy, subject);
+  }
+
+  public And<LogsSubject> hasNoLogsAtLevel(Level level) {
+    for (LogRecord log : getSubject().getStoredLogRecords()) {
+      if (log.getLevel() == level) {
+        failWithRawMessage(
+            "Not true that there are no logs at level %s. Found <%s>.", level, log.getMessage());
+      }
+    }
+    return new And<>(this);
+  }
+
+  public And<LogsSubject> hasLogAtLevelWithMessage(Level level, String message) {
+    boolean found = false;
+    for (LogRecord log : getSubject().getStoredLogRecords()) {
+      if (log.getLevel() == level && log.getMessage().contains(message)) {
+        found = true;
+        break;
+      }
+    }
+    if (!found) {
+      failWithRawMessage("Found no logs at level %s with message %s.", level, message);
+    }
+    return new And<>(this);
+  }
+
+  public static DelegatedVerb<LogsSubject, TestLogHandler> assertAboutLogs() {
+    return assertAbout(new SubjectFactory());
+  }
+}