Add tests, fix header

Author: JonasKunz

libs/exponential-histogram/build.gradle

@@ -19,6 +19,7 @@ dependencies {
   testImplementation(project(":test:framework"))
   testImplementation('ch.obermuhlner:big-math:2.3.2')
   testImplementation('org.apache.commons:commons-math3:3.6.1')
+  testImplementation project(':libs:x-content:impl')
 }
 
 tasks.named('forbiddenApisMain').configure {

libs/exponential-histogram/src/main/java/org/elasticsearch/exponentialhistogram/ExponentialHistogramXContent.java

@@ -1,10 +1,22 @@
 /*
- * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
- * or more contributor license agreements. Licensed under the "Elastic License
- * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
- * Public License v 1"; you may not use this file except in compliance with, at
- * your election, the "Elastic License 2.0", the "GNU Affero General Public
- * License v3.0 only", or the "Server Side Public License, v 1".
+ * Copyright Elasticsearch B.V., and/or licensed to Elasticsearch B.V.
+ * under one or more license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you 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.
+ *
+ * This file is based on a modification of https://github.com/open-telemetry/opentelemetry-java which is licensed under the Apache 2.0 License.
  */
 
 package org.elasticsearch.exponentialhistogram;

libs/exponential-histogram/src/test/java/org/elasticsearch/exponentialhistogram/ExponentialHistogramXContentTests.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright Elasticsearch B.V., and/or licensed to Elasticsearch B.V.
+ * under one or more license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you 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.
+ *
+ * This file is based on a modification of https://github.com/open-telemetry/opentelemetry-java which is licensed under the Apache 2.0 License.
+ */
+
+package org.elasticsearch.exponentialhistogram;
+
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.xcontent.XContentBuilder;
+import org.elasticsearch.xcontent.json.JsonXContent;
+
+import java.io.IOException;
+
+import static org.hamcrest.Matchers.equalTo;
+
+public class ExponentialHistogramXContentTests extends ExponentialHistogramTestCase {
+
+    public void testEmptyHistogram() {
+        ExponentialHistogram emptyHistogram = ExponentialHistogram.empty();
+        assertSerializedHistogram(ExponentialHistogram.empty(), "{\"scale\":" + emptyHistogram.scale() + "}");
+    }
+
+    public void testFullHistogram() {
+        FixedCapacityExponentialHistogram histo = createAutoReleasedHistogram(100);
+        histo.setZeroBucket(new ZeroBucket(0.1234, 42));
+        histo.resetBuckets(7);
+        histo.tryAddBucket(-10, 15, false);
+        histo.tryAddBucket(10, 5, false);
+        histo.tryAddBucket(-11, 10, true);
+        histo.tryAddBucket(11, 20, true);
+        assertSerializedHistogram(
+            histo,
+            "{"
+                + "\"scale\":7,"
+                + "\"zero\":{\"count\":42,\"threshold\":0.1234},"
+                + "\"positive\":{\"indices\":[-11,11],\"counts\":[10,20]},"
+                + "\"negative\":{\"indices\":[-10,10],\"counts\":[15,5]}"
+                + "}"
+        );
+
+    }
+
+    public void testOnlyZeroThreshold() {
+        FixedCapacityExponentialHistogram histo = createAutoReleasedHistogram(10);
+        histo.setZeroBucket(new ZeroBucket(5.0, 0));
+        histo.resetBuckets(3);
+        assertSerializedHistogram(histo, "{\"scale\":3,\"zero\":{\"threshold\":5.0}}");
+    }
+
+    public void testOnlyZeroCount() {
+        FixedCapacityExponentialHistogram histo = createAutoReleasedHistogram(10);
+        histo.setZeroBucket(new ZeroBucket(0.0, 7));
+        histo.resetBuckets(2);
+        assertSerializedHistogram(histo, "{\"scale\":2,\"zero\":{\"count\":7}}");
+    }
+
+    public void testOnlyPositiveBuckets() {
+        FixedCapacityExponentialHistogram histo = createAutoReleasedHistogram(10);
+        histo.resetBuckets(4);
+        histo.tryAddBucket(-1, 3, true);
+        histo.tryAddBucket(2, 5, true);
+        assertSerializedHistogram(histo, "{\"scale\":4,\"positive\":{\"indices\":[-1,2],\"counts\":[3,5]}}");
+    }
+
+    public void testOnlyNegativeBuckets() {
+        FixedCapacityExponentialHistogram histo = createAutoReleasedHistogram(10);
+        histo.resetBuckets(5);
+        histo.tryAddBucket(-1, 4, false);
+        histo.tryAddBucket(2, 6, false);
+        assertSerializedHistogram(histo, "{\"scale\":5,\"negative\":{\"indices\":[-1,2],\"counts\":[4,6]}}");
+    }
+
+    private static void assertSerializedHistogram(ExponentialHistogram histo, String expectedJson) {
+        try (XContentBuilder builder = JsonXContent.contentBuilder()) {
+            ExponentialHistogramXContent.serialize(builder, histo);
+            assertThat(Strings.toString(builder), equalTo(expectedJson));
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+}