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EXERCISE2.md

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2. Use the Red Green Refactor workflow to implement a solution

There is a class in ./src/main/java/com.booleanuk/code/CohortManager.java and a test class in ./src/test/java/com.booleanuk/core/CohortManagerTest.java. Your morning teacher will demonstrate the process of creating tests from the domain model below, and then using those tests to develop robust source code.

This is known as the Red, Green, Refactor workflow; an important discipline to practice. Simple to learn yet difficult to master.

When writing software using this Test Driven Development approach, we don't write a complete test or complete method at a time. We write just enough of a test for it to fail, then write just enough source code to make the test pass, then refactor until the test fails and repeat this cycle.

What we are creating here are known as unit tests, tests that verify a single unit of our application is working correctly. They should be as small as possible, usually broken down into three parts:

  1. Setup
  2. Execute
  3. Verify

Here's some pseudo-code to show the structure of a unit test:

shouldSayHello() {
    // 1. Set up
    speaker = new Speaker();
    name = "Nathan";
    
    // 2. Execute
    message = speaker.sayHello(name)
    
    // 3. Verify
    assertEquals("Hello, Nathan!", message)
}

Domain model for demonstration

As a user,
So I can find a specific cohort,
I want to search a list of all cohorts by a cohort name.
Classes Methods Scenario Outputs
CohortManager search(List<String> cohorts, String name) If name is in list true
If name is not in list false

Exercise

NOTE: Create new classes in the ./src/main/java/com.booleanuk/core/ directory

NOTE: Create new test classes in the ./src/test/java/com.booleanuk/core/ directory

  • Use the Red, Green, Refactor approach to create a solution for the following domain model
  • It's normal for this practice to feel difficult or frustrating in the beginning
As a supermarket shopper,
So that I can restock my cupboards,
I want to add products into my basket.

As a supermarket shopper,
So that I can pay for products at checkout,
I'd like to be able to know the total cost of items in my basket.
Classes Members Methods Scenario Outputs
Basket HashMap<String, int> items (key is product name, value is price) add(String product, int price) Item with the provided name is not already in the basket true
Item with the provided name is already in the basket false
total() int