Gauge API : Add support for DerivedDoubleGauge (#1504)

* Add support for DerivedDoubleGauge

* Fix review comments

* Fix reviews

1 files changed, 89 insertions, 0 deletions

diff --git a/api/src/test/java/io/opencensus/metrics/DerivedDoubleGaugeTest.java b/api/src/test/java/io/opencensus/metrics/DerivedDoubleGaugeTest.java
new file mode 100644
index 00000000..dbae3c49
--- /dev/null
+++ b/api/src/test/java/io/opencensus/metrics/DerivedDoubleGaugeTest.java
@@ -0,0 +1,89 @@
+/*
+ * 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.metrics;
+
+import io.opencensus.common.ToDoubleFunction;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link DerivedDoubleGauge}. */
+// TODO(mayurkale): Add more tests, once DerivedDoubleGauge plugs-in into the registry.
+@RunWith(JUnit4.class)
+public class DerivedDoubleGaugeTest {
+  @Rule public ExpectedException thrown = ExpectedException.none();
+
+  private static final String NAME = "name";
+  private static final String DESCRIPTION = "description";
+  private static final String UNIT = "1";
+  private static final List<LabelKey> LABEL_KEY =
+      Collections.singletonList(LabelKey.create("key", "key description"));
+  private static final List<LabelValue> LABEL_VALUES =
+      Collections.singletonList(LabelValue.create("value"));
+  private static final List<LabelValue> EMPTY_LABEL_VALUES = new ArrayList<LabelValue>();
+
+  private final DerivedDoubleGauge derivedDoubleGauge =
+      DerivedDoubleGauge.newNoopDerivedDoubleGauge(NAME, DESCRIPTION, UNIT, LABEL_KEY);
+  private static final ToDoubleFunction<Object> doubleFunction =
+      new ToDoubleFunction<Object>() {
+        @Override
+        public double applyAsDouble(Object value) {
+          return 5.0;
+        }
+      };
+
+  @Test
+  public void noopCreateTimeSeries_WithNullLabelValues() {
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage("labelValues");
+    derivedDoubleGauge.createTimeSeries(null, null, doubleFunction);
+  }
+
+  @Test
+  public void noopCreateTimeSeries_WithNullElement() {
+    List<LabelValue> labelValues = Collections.singletonList(null);
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage("labelValue element should not be null.");
+    derivedDoubleGauge.createTimeSeries(labelValues, null, doubleFunction);
+  }
+
+  @Test
+  public void noopCreateTimeSeries_WithInvalidLabelSize() {
+    thrown.expect(IllegalArgumentException.class);
+    thrown.expectMessage("Incorrect number of labels.");
+    derivedDoubleGauge.createTimeSeries(EMPTY_LABEL_VALUES, null, doubleFunction);
+  }
+
+  @Test
+  public void createTimeSeries_WithNullFunction() {
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage("function");
+    derivedDoubleGauge.createTimeSeries(LABEL_VALUES, null, null);
+  }
+
+  @Test
+  public void noopRemoveTimeSeries_WithNullLabelValues() {
+    thrown.expect(NullPointerException.class);
+    thrown.expectMessage("labelValues");
+    derivedDoubleGauge.removeTimeSeries(null);
+  }
+}