### Question:
BivariateDataStatisticsCalculator { public long size() { return xData.getLength(); } BivariateDataStatisticsCalculator(DoubleTensor xData, DoubleTensor yData); long size(); double xMean(); double yMean(); double estimatedGradient(); double estimatedIntercept(); double meanSquaredError(); double standardErrorForGradient(); double standardErrorForIntercept();  }### Answer:
@Test public void youCanGetTheNumberOfSamples() { assertThat(stats.size(), equalTo(xStats.getN())); }