On page 241 of the PDF in listing utj3-tdd/31/src/test/java/app/APortfolio.java, the arguments to assertEquals are reversed. Instead of

assertEquals(portfolio.lastTransaction(), new Transaction("SONO", 20, BUY, now));

they should be

assertEquals(new Transaction("SONO", 20, BUY, now), portfolio.lastTransaction());

The arguments are also reversed in various tests on later pages in these listings:
* utj3-tdd/32/src/test/java/app/APortfolio.java
* utj3-tdd/33/src/test/java/app/APortfolio.java