[Test] Add unit tests for InternalTDigestPercentilesTests (#24090)

Author: tlrx

core/src/test/java/org/elasticsearch/search/aggregations/metrics/percentiles/tdigest/InternalTDigestPercentilesTests.java

@@ -0,0 +1,81 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch 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.
+ */
+
+package org.elasticsearch.search.aggregations.metrics.percentiles.tdigest;
+
+import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.search.DocValueFormat;
+import org.elasticsearch.search.aggregations.InternalAggregationTestCase;
+import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
+
+import java.util.List;
+import java.util.Map;
+
+public class InternalTDigestPercentilesTests extends InternalAggregationTestCase<InternalTDigestPercentiles> {
+
+    private final double[] percents = randomPercents();
+
+    @Override
+    protected InternalTDigestPercentiles createTestInstance(String name,
+                                                            List<PipelineAggregator> pipelineAggregators,
+                                                            Map<String, Object> metaData) {
+        boolean keyed = randomBoolean();
+        DocValueFormat format = DocValueFormat.RAW;
+        TDigestState state = new TDigestState(100);
+
+        int numValues = randomInt(10);
+        for (int i = 0; i < numValues; ++i) {
+            state.add(randomDouble() * 100);
+        }
+        assertEquals(state.centroidCount(), numValues);
+        return new InternalTDigestPercentiles(name, percents, state, keyed, format, pipelineAggregators, metaData);
+    }
+
+    @Override
+    protected void assertReduced(InternalTDigestPercentiles reduced, List<InternalTDigestPercentiles> inputs) {
+        final TDigestState expectedState = new TDigestState(reduced.state.compression());
+
+        long totalCount = 0;
+        for (InternalTDigestPercentiles input : inputs) {
+            assertArrayEquals(reduced.keys, input.keys, 0d);
+            expectedState.add(input.state);
+            totalCount += input.state.size();
+        }
+
+        assertEquals(totalCount, reduced.state.size());
+        if (totalCount > 0) {
+            assertEquals(expectedState.quantile(0), reduced.state.quantile(0), 0d);
+            assertEquals(expectedState.quantile(1), reduced.state.quantile(1), 0d);
+        }
+    }
+
+    @Override
+    protected Writeable.Reader<InternalTDigestPercentiles> instanceReader() {
+        return InternalTDigestPercentiles::new;
+    }
+
+    private static double[] randomPercents() {
+        List<Double> randomCdfValues = randomSubsetOf(randomIntBetween(1, 7), 0.01d, 0.05d, 0.25d, 0.50d, 0.75d, 0.95d, 0.99d);
+        double[] percents = new double[randomCdfValues.size()];
+        for (int i = 0; i < randomCdfValues.size(); i++) {
+            percents[i] = randomCdfValues.get(i);
+        }
+        return percents;
+    }
+}