Pragmatic Unit Testing in Java with JUnit, 3rd Edition

Increment 3: Factoring Out Redundancies

Your next challenge: support selling shares of a stock. There’s not much point in buying stocks in the first place if you can’t sell them.

Madhu discusses the requirements with you:

• Reduce shares of a holding when selling stocks.
• Throw an exception on attempts to sell more shares of a symbol than what is held.

Joe says, “okay,” then pauses a moment and asks, “what happens if you sell all the shares of a stock? The portfolio’s size—its count of unique symbols held—should come down by one, right?”

Madhu says, “Yes, a good thought, and let’s make sure we test for that.”

You both nod to Madhu and then turn to the monitor to code the first test:

utj3-tdd/26/src/test/java/app/APortfolio.java

@Test
void reducesSharesOnSell ...