sdks/java/extensions/sql/src/test/java/org/apache/beam/sdk/extensions/sql/impl/LazyAggregateCombineFnTest.java

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 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
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 *     http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.beam.sdk.extensions.sql.impl;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.instanceOf;
import static org.junit.Assert.assertEquals;

import org.apache.beam.sdk.coders.CannotProvideCoderException;
import org.apache.beam.sdk.coders.Coder;
import org.apache.beam.sdk.coders.CoderRegistry;
import org.apache.beam.sdk.coders.VarLongCoder;
import org.apache.beam.sdk.extensions.sql.udf.AggregateFn;
import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.ImmutableList;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/** Tests for {@link LazyAggregateCombineFn}. */
@RunWith(JUnit4.class)
public class LazyAggregateCombineFnTest {

  @Test
  public void getAccumulatorCoderInfersCoderForWildcardTypeParameter()
      throws CannotProvideCoderException {
    LazyAggregateCombineFn<Long, ?, ?> combiner = new LazyAggregateCombineFn<>(new Sum());
    Coder<?> coder = combiner.getAccumulatorCoder(CoderRegistry.createDefault(), VarLongCoder.of());
    assertThat(coder, instanceOf(VarLongCoder.class));
  }

  @Test
  public void mergeAccumulators() {
    LazyAggregateCombineFn<Long, Long, Long> combiner = new LazyAggregateCombineFn<>(new Sum());
    long merged = combiner.mergeAccumulators(ImmutableList.of(1L, 1L));
    assertEquals(2L, merged);
  }

  public static class Sum implements AggregateFn<Long, Long, Long> {

    @Override
    public Long createAccumulator() {
      return 0L;
    }

    @Override
    public Long addInput(Long mutableAccumulator, Long input) {
      return mutableAccumulator + input;
    }

    @Override
    public Long mergeAccumulators(Long mutableAccumulator, Iterable<Long> immutableAccumulators) {
      for (Long x : immutableAccumulators) {
        mutableAccumulator += x;
      }
      return mutableAccumulator;
    }

    @Override
    public Long extractOutput(Long mutableAccumulator) {
      return mutableAccumulator;
    }
  }
}