Let the participants retroactively create test cases for the following function:
def remove_prefix(pattern, string): """Removes the given regular expression pattern from the beginning of the string.""" return re.sub(r"^" + pattern, "", string)
Before moving on, point out the logic contained in the function: Removes the given regular expression pattern from the beginning of the string.
You want to test:
You do not want to
Compare: If the function was written using strict TDD, which tests would you end up with?
Highlight the following quote from Joshua Bloch: “Public APIs, like diamonds, are forever.”
Present the following principles:
This approach relies on the code being cohesive and decoupled (“well refactored”).
Use red-green-refactor (and triangulation) to get tests that test the new/changed behavior. Avoids testing already tested behavior from reused functions. Just as with the Connect exercise, you do not want to retest reused functionality.
Do not blindly copy the old tests and code.
Will generally keep the code well refactored.
Might seem like a lot of work for large systems, but the payoff is greater the larger the system.
You have an existing fizzbuzz-like program, with a main file that gives the desired output.
1: One 2: Two 3: Fizz 4: Four 5: Buzz 6: Fizz 7: Whazz 8: Eight ... 105: FizzBuzzWhazz
A new rule should be added: every prime number should be shouted (i.e. all caps). A prime number is a positive integer evenly divisible by only two numbers (only by 1 and itself; one is not a prime number).
1: One 2: TWO 3: FIZZ 4: Four 5: BUZZ 6: Fizz 7: WHAZZ 8: Eight ... 105: FizzBuzzWhazz
Implement this change without breaking or rewriting any existing unit tests, by first creating a function
shouting_fizzbuzzwhazz, and then swapping out
fizzbuzzwhazz in main.
The main program should contain the following functions and corresponding tests:
fizzbuzzwhazz(like fizzbuzz, but also “Whazz” for numbers divisible by 7 and combinations, e.g. 3*5*7=105 gives “FizzBuzzWhazz”).
is_prime: returns true if the argument is a prime number, else false.
main: prints the output, using
Compare the tests for
is_prime respectively. How well does the tests align with the functionality that the respective function provides? Is
shouting_fizzbuzzwhazz retesting the fizzbuzz logic or prime checks?