iOS Unit Testing by Example: Include example of deleting production code (page 48)

The statement “If you can delete lines of production code and the tests still pass, then those lines aren’t covered,” was important enough to be repeated in the Key Takeaways section on page 50, but it is easily missed in the chapter body.

Perhaps include an exercise where you delete the calls to redOrGreen(for:) and drawSquare(width:Color:) to emphasize the statement.

John Brewer