StopFailingService service = new StopFailingService();
    assertThrows(IllegalStateException.class, () -> service.failureCause());
    service.startAsync().awaitRunning();
    assertThrows(IllegalStateException.class, () -> service.failureCause());
    IllegalStateException e =
        assertThrows(IllegalStateException.class, () -> service.stopAsync().awaitTerminated());
    assertEquals(EXCEPTION, service.failureCause());

  }

  public void testPearsonsCorrelationCoefficient() {
    assertThrows(
        IllegalStateException.class, () -> EMPTY_PAIRED_STATS.pearsonsCorrelationCoefficient());
    assertThrows(
        IllegalStateException.class, () -> ONE_VALUE_PAIRED_STATS.pearsonsCorrelationCoefficient());
    assertThrows(
        IllegalStateException.class,
        () -> createSingleStats(Double.POSITIVE_INFINITY, 1.23).pearsonsCorrelationCoefficient());

  }

  public void testPearsonsCorrelationCoefficient() {
    assertThrows(
        IllegalStateException.class, () -> EMPTY_PAIRED_STATS.pearsonsCorrelationCoefficient());
    assertThrows(
        IllegalStateException.class, () -> ONE_VALUE_PAIRED_STATS.pearsonsCorrelationCoefficient());
    assertThrows(
        IllegalStateException.class,
        () -> createSingleStats(Double.POSITIVE_INFINITY, 1.23).pearsonsCorrelationCoefficient());

  public void testSampleVariance() {
    assertThrows(IllegalStateException.class, () -> emptyAccumulator.sampleVariance());
    assertThrows(
        IllegalStateException.class, () -> emptyAccumulatorByAddAllEmptyIterable.sampleVariance());
    assertThrows(
        IllegalStateException.class, () -> emptyAccumulatorByAddAllEmptyStats.sampleVariance());
    assertThrows(IllegalStateException.class, () -> oneValueAccumulator.sampleVariance());

   * involving any parameters to the calling method.
   *
   * @param expression a boolean expression
   * @throws IllegalStateException if {@code expression} is false
   * @see Verify#verify Verify.verify()
   */
  public static void checkState(boolean expression) {
    if (!expression) {
      throw new IllegalStateException();
    }
  }

  /**

  }

  public void testSampleVariance() {
    assertThrows(IllegalStateException.class, () -> EMPTY_STATS_VARARGS.sampleVariance());
    assertThrows(IllegalStateException.class, () -> EMPTY_STATS_ITERABLE.sampleVariance());
    assertThrows(IllegalStateException.class, () -> ONE_VALUE_STATS.sampleVariance());
    assertThat(TWO_VALUES_STATS.sampleVariance())
        .isWithin(ALLOWED_ERROR)

    }

    @Override
    Comparable<?> endpoint() {
      throw new IllegalStateException("range unbounded on this side");
    }

    @Override
    boolean isLessThan(Comparable<?> value) {
      return true;
    }

    @Override
    BoundType typeAsLowerBound() {
      throw new IllegalStateException();
    }

    @Override
    BoundType typeAsUpperBound() {

      fail();
    } catch (IllegalStateException expected) {
    }
    assertTrue(stopwatch.isRunning());
  }

  public void testStop() {
    stopwatch.start();
    assertSame(stopwatch, stopwatch.stop());
    assertFalse(stopwatch.isRunning());
  }

  public void testStop_new() {
    try {
      stopwatch.stop();
      fail();
    } catch (IllegalStateException expected) {
    }

    StopFailingService service = new StopFailingService();
    assertThrows(IllegalStateException.class, () -> service.failureCause());
    service.startAsync().awaitRunning();
    assertThrows(IllegalStateException.class, () -> service.failureCause());
    IllegalStateException e =
        assertThrows(IllegalStateException.class, () -> service.stopAsync().awaitTerminated());
    assertEquals(EXCEPTION, service.failureCause());

      default:
        throw new IllegalStateException("Unexpected edge type: " + edgeType);
    }
  }

  private static EdgeType oppositeType(EdgeType edgeType) {
    switch (edgeType) {
      case UNDIRECTED:
        return EdgeType.DIRECTED;
      case DIRECTED:
        return EdgeType.UNDIRECTED;
      default:
        throw new IllegalStateException("Unexpected edge type: " + edgeType);
    }
  }