@Test
public void computeStockWorth() {

    // Note how easy it is, with lambdas, to "stub" out the priceFinder
    final CalculateNAV calculateNAV = new CalculateNAV( ticker -> new BigDecimal( "6.01" ) );
    BigDecimal expected = new BigDecimal( "6010.00" );
    // I was unaware of the delta thing.
    assertEquals( 0, calculateNAV.computeStockWorth( "GOOG", 1000 )
            .compareTo( expected ), 0.001 );
}