[TEST] Restructure MovAvgTests to be more generic, robust

src/test/java/org/elasticsearch/search/aggregations/reducers/ReducerTestHelpers.java

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+/*
+ * 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.reducers;
+
+
+import org.elasticsearch.search.aggregations.metrics.ValuesSourceMetricsAggregationBuilder;
+import org.elasticsearch.search.aggregations.metrics.avg.AvgBuilder;
+import org.elasticsearch.search.aggregations.metrics.max.MaxBuilder;
+import org.elasticsearch.search.aggregations.metrics.min.MinBuilder;
+import org.elasticsearch.search.aggregations.metrics.sum.SumBuilder;
+import org.elasticsearch.test.ElasticsearchTestCase;
+
+import java.util.ArrayList;
+
+/**
+ * Provides helper methods and classes for use in Reducer tests, such as creating mock histograms or computing
+ * simple metrics
+ */
+public class ReducerTestHelpers extends ElasticsearchTestCase {
+
+    /**
+     * Generates a mock histogram to use for testing.  Each MockBucket holds a doc count, key and document values
+     * which can later be used to compute metrics and compare against the real aggregation results.  Gappiness can be
+     * controlled via parameters
+     *
+     * @param interval          Interval between bucket keys
+     * @param size              Size of mock histogram to generate (in buckets)
+     * @param gapProbability    Probability of generating an empty bucket. 0.0-1.0 inclusive
+     * @param runProbability    Probability of extending a gap once one has been created.  0.0-1.0 inclusive
+     * @return
+     */
+    public static ArrayList<MockBucket> generateHistogram(int interval, int size, double gapProbability, double runProbability) {
+        ArrayList<MockBucket> values = new ArrayList<>(size);
+
+        boolean lastWasGap = false;
+
+        for (int i = 0; i < size; i++) {
+            MockBucket bucket = new MockBucket();
+            if (randomDouble() < gapProbability) {
+                // start a gap
+                bucket.count = 0;
+                bucket.docValues = new double[0];
+
+                lastWasGap = true;
+
+            } else if (lastWasGap && randomDouble() < runProbability) {
+                // add to the existing gap
+                bucket.count = 0;
+                bucket.docValues = new double[0];
+
+                lastWasGap = true;
+            } else {
+                bucket.count = randomIntBetween(1, 50);
+                bucket.docValues = new double[bucket.count];
+                for (int j = 0; j < bucket.count; j++) {
+                    bucket.docValues[j] = randomDouble() * randomIntBetween(-20,20);
+                }
+                lastWasGap = false;
+            }
+
+            bucket.key = i * interval;
+            values.add(bucket);
+        }
+
+        return values;
+    }
+
+    /**
+     * Simple mock bucket container
+     */
+    public static class MockBucket {
+        public int count;
+        public double[] docValues;
+        public long key;
+    }
+
+    /**
+     * Computes a simple agg metric (min, sum, etc) from the provided values
+     *
+     * @param values Array of values to compute metric for
+     * @param metric A metric builder which defines what kind of metric should be returned for the values
+     * @return
+     */
+    public static double calculateMetric(double[] values, ValuesSourceMetricsAggregationBuilder metric) {
+
+        if (metric instanceof MinBuilder) {
+            double accumulator = Double.MAX_VALUE;
+            for (double value : values) {
+                accumulator = Math.min(accumulator, value);
+            }
+            return accumulator;
+        } else if (metric instanceof MaxBuilder) {
+            double accumulator = Double.MIN_VALUE;
+            for (double value : values) {
+                accumulator = Math.max(accumulator, value);
+            }
+            return accumulator;
+        } else if (metric instanceof SumBuilder) {
+            double accumulator = 0;
+            for (double value : values) {
+                accumulator += value;
+            }
+            return accumulator;
+        } else if (metric instanceof AvgBuilder) {
+            double accumulator = 0;
+            for (double value : values) {
+                accumulator += value;
+            }
+            return accumulator / values.length;
+        }
+
+        return 0.0;
+    }
+}