Metrics: Implement ExportComponent, make ProducerManager abstract. (#1347)

* Metrics: Implement ExportComponent, make ProducerManager abstract.

* Metrics: Add impl and impllite.

* Resolve two TODOs.

* Fix import path, leave a TODO for getMetricRegistry.

* Make NoopMetricProducerManager private. Add missing since tag.

1 files changed, 36 insertions, 0 deletions

diff --git a/impl_lite/src/test/java/io/opencensus/impllite/metrics/MetricsTest.java b/impl_lite/src/test/java/io/opencensus/impllite/metrics/MetricsTest.java
new file mode 100644
index 00000000..ab8889a9
--- /dev/null
+++ b/impl_lite/src/test/java/io/opencensus/impllite/metrics/MetricsTest.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2018, OpenCensus Authors
+ *
+ * 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 io.opencensus.impllite.metrics;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import io.opencensus.implcore.metrics.export.ExportComponentImpl;
+import io.opencensus.metrics.Metrics;
+import io.opencensus.metrics.MetricsComponent;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Test for accessing the {@link MetricsComponent} through the {@link Metrics} class. */
+@RunWith(JUnit4.class)
+public class MetricsTest {
+
+  @Test
+  public void getExportComponent() {
+    assertThat(Metrics.getExportComponent()).isInstanceOf(ExportComponentImpl.class);
+  }
+}