nl.topicus.jdbc.shaded.com.google.api.gax.core.DistributionTest Maven / Gradle / Ivy

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package nl.topicus.jdbc.shaded.com.google.api.gax.core;

import static nl.topicus.jdbc.shaded.com.google.common.truth.Truth.assertThat;

import java.util.Arrays;
import java.util.Collections;
import org.junit.Test;

public class DistributionTest {
  @Test
  public void testPercentile() {
    // These tests come from examples in https://en.wikipedia.org/wiki/Percentile#The_nearest-rank_method
    Distribution dist;

    dist = of(15, 20, 35, 40, 50);
    assertThat(dist.getPercentile(5)).isEqualTo(15);
    assertThat(dist.getPercentile(30)).isEqualTo(20);
    assertThat(dist.getPercentile(40)).isEqualTo(20);
    assertThat(dist.getPercentile(50)).isEqualTo(35);
    assertThat(dist.getPercentile(100)).isEqualTo(50);

    dist = of(3, 6, 7, 8, 8, 10, 13, 15, 16, 20);
    assertThat(dist.getPercentile(25)).isEqualTo(7);
    assertThat(dist.getPercentile(50)).isEqualTo(8);
    assertThat(dist.getPercentile(75)).isEqualTo(15);
    assertThat(dist.getPercentile(100)).isEqualTo(20);

    dist = of(3, 6, 7, 8, 8, 9, 10, 13, 15, 16, 20);
    assertThat(dist.getPercentile(25)).isEqualTo(7);
    assertThat(dist.getPercentile(50)).isEqualTo(9);
    assertThat(dist.getPercentile(75)).isEqualTo(15);
    assertThat(dist.getPercentile(100)).isEqualTo(20);
  }

  @Test(expected = IllegalArgumentException.class)
  public void testZeroMaxValue() {
    new Distribution(0);
  }

  @Test(expected = IllegalArgumentException.class)
  public void testNegativeMaxValue() {
    new Distribution(-1);
  }

  @Test
  public void testOverflowMaxValue() {
    // Record value greater than maxValue-1 is OK. We record maxValue-1 instead.
    Distribution dist = new Distribution(10);
    dist.record(10);
    assertThat(dist.getPercentile(100)).isEqualTo(9);
  }

  private Distribution of(Integer... values) {
    int max = Collections.max(Arrays.asList(values));
    Distribution dist = new Distribution(max + 1);
    for (int value : values) {
      dist.record(value);
    }
    return dist;
  }
}