Fizzbuzz

Connection

Introduce yourself to a person near you and discuss.

Is it easier to unit test :

- a static method
- pure function
- method that modifies object state
- method that modifies its parameters

The reason for asking about what is easy to test is to get them prepared for designing a pure function or static method for calculating FizzBuzz.

These kinds of functions are easier to test since all the outcomes are visible in the return value, the input value is not modified and there are no side effects.

Concepts

Bust the TDD myths

• TDD is too Time Consuming

  • The business team doesn’t care at all about the development process you use, as long as it’s effective.

  • TDD will :

    • improve developer productivity (long term)

    • Reduce customer abandonment

    • Reduce the costs of customer service

• Writing test cases before the code, is not feasible

  • It forces you to have a direction in mind before you start charging into the fray, and having a direction in mind leads to better designs

• 100% code coverage

  • 100% of testing the wrong things is not a goal…

  • Focus on the value

• TDD replaces QA

  • We can’t cover everything with TDD

  • For example : GUI E2E tests (really hard to maintain)

  • This is where QA has an important role.

• Write all tests before we start the code

  • Not at all : 1 test at a time

2 TDD schools

Chicago / Detroit TDD (Classic)	London TDD (Mockist approach)
From the inside to outside	From the outside to inside
Starting from the model classes (Core domain logic)	Use external constraints as a starting point (API endpoint, Services)
No concern for how it might be integrated elsewhere

Concrete Practice

Write a method that returns for a number from 1 to 100 this given number, except that :

• For multiples of 3 returns “Fizz”

• For the multiples of 5 returns “Buzz”

• For numbers which are multiples of both 3 and 5 returns “FizzBuzz”

Let them start for 10' then reflect you can then give them more guidance :

1) Identify your Test Cases

By using the Test Cards in pair : identify test cases

How would you name your first test ?

• Ask attendees to note on a Sticky Note what is the name of their first test

• Compare the different styles

• What do they prefer (Dot voting)

How to name Good Unit Tests ? (GUTs)

How to name our Unit Tests

Fizzbuzz Test cases :

- shouldReturnTheNumber (ex : 1, 67, 82, ...)
- shouldReturnFizzForMultipleOf3 (ex : 3, 30, 99)
- shouldReturnBuzzForMultipleOf5 (ex : 5, 50, 85)
- shouldReturnFizzBuzzForMultipleOf3And5 (ex : 15, 30, 45)
- shouldThrowAnExceptionForNumberOutOfRange (ex : 0, -1, 101)

2) Once identified the 5 Test Cases, write the code

By using TDD, write Test cases once at a time :

Trap to avoid : "do not write 1 test to rule them all"

• Talks about sampling

  • Tests are always a sample

  • You cannot cover every possible value

• Do not repeat the same complexity in your tests than in your Production Code

3) A little bit to easy ?

• Remove “if” in your code

• Parameters version, implement this method :

  • If you use a language authorizing default values :

    • int limit : 100

    • int fizz : 3

    • int buzz : 5

public class FizzBuzz {
    public String fizzBuzz(int limit, int fizz, int buzz) {
        ...
    }
}

• Take a function in parameter

  • Create a Higher Order Function : function modulo(dividend, divisor){ return dividend%divisor; }

• Add a voice output

• Write it in an unknown language

Reflect

• What happened to your code when implementing new tests ?

Triangulation : The more specific tests you write, the more the code will become generic

Conclusion

• In pairs, discuss how TDD felt, what was difficult and what was easier.

• Tell the other person the most useful thing you learnt today.