On page 90, CalculateNAVTest.java:

public class CalculateNAVTest {

   @Test
   public void computeStockWorth() {
      final CalculateNAV calculateNAV = new CalculateNAV(ticker -> new BigDecimal("6.01"));
      BigDecimal expected = new BigDecimal("6010.00");
      assertEquals(0, calculateNAV.computeStockWorth("GOOG", 1000).compareTo(expected), 0.001);
   }

The assertEquals() makes no sense.

It runs BigDecimal.compare( new BigDecimal("6010") , new BigDecimal("6010.00") ) which is either -1, 0 or +1, and compares it with 0 with an irrelevant precision of 0.001.

What we want is:

public class CalculateNAVTest {

   @Test
    public void computeStockWorth() {
        final CalculateNAV calculateNAV = new CalculateNAV(ticker -> new BigDecimal("6.01"));
        BigDecimal expected = new BigDecimal("6010.00");
        BigDecimal actual = calculateNAV.computeStockWorth("GOOG", 1000);
        BigDecimal delta = actual.subtract(expected);
        assertEquals(delta.doubleValue(), 0, 0.001);
    }

JavaDoc for BigDecimal.compare():