Add flow-level EPP metric tests

This also adds an assertion helper for EPP metrics.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=154458134

javatests/google/registry/testing/EppMetricSubject.java

@@ -0,0 +1,78 @@
+// Copyright 2017 The Nomulus 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 google.registry.testing;
+
+import static com.google.common.truth.Truth.assertAbout;
+import static google.registry.util.PreconditionsUtils.checkArgumentNotNull;
+
+import com.google.common.base.Optional;
+import com.google.common.truth.FailureStrategy;
+import com.google.common.truth.Subject;
+import com.google.common.truth.SubjectFactory;
+import google.registry.model.eppoutput.Result.Code;
+import google.registry.monitoring.whitebox.EppMetric;
+import google.registry.testing.TruthChainer.And;
+import java.util.Objects;
+import javax.annotation.Nullable;
+
+/** Utility methods for asserting things about {@link EppMetric} instances. */
+public class EppMetricSubject extends Subject<EppMetricSubject, EppMetric> {
+
+  public EppMetricSubject(FailureStrategy strategy, EppMetric subject) {
+    super(strategy, subject);
+  }
+
+  public static EppMetricSubject assertThat(EppMetric subject) {
+    return assertAbout(SUBJECT_FACTORY).that(subject);
+  }
+
+  public And<EppMetricSubject> hasClientId(String clientId) {
+    return hasValue(clientId, actual().getClientId(), "has clientId");
+  }
+
+  public And<EppMetricSubject> hasCommandName(String commandName) {
+    return hasValue(commandName, actual().getCommandName(), "has commandName");
+  }
+
+  public And<EppMetricSubject> hasEppTarget(String eppTarget) {
+    return hasValue(eppTarget, actual().getEppTarget(), "has eppTarget");
+  }
+
+  public And<EppMetricSubject> hasStatus(Code status) {
+    return hasValue(status, actual().getStatus(), "has status");
+  }
+
+  private <E> And<EppMetricSubject> hasValue(E expected, Optional<E> actual, String verb) {
+    checkArgumentNotNull(expected, "Expected value cannot be null");
+    if (actual == null) {
+      fail("is non-null", expected);
+    } else if (!actual.isPresent()) {
+      fail("has value", expected);
+    } else if (!Objects.equals(expected, actual.get())) {
+      failWithBadResults(verb, expected, verb, actual);
+    }
+    return new And<>(this);
+  }
+
+  /** {@link SubjectFactory} for assertions about {@link EppMetric} objects. */
+  private static final SubjectFactory<EppMetricSubject, EppMetric> SUBJECT_FACTORY =
+      new SubjectFactory<EppMetricSubject, EppMetric>() {
+        @Override
+        public EppMetricSubject getSubject(
+            FailureStrategy failureStrategy, @Nullable EppMetric target) {
+          return new EppMetricSubject(failureStrategy, target);
+        }
+      };
+}