TDD-AnimalFactory-BlueJ/README-TDDPatterns.md

Test Driven Development (TDD)

What is a unit test?

• A unit test is a practice by which small units of code are tested.
• The purpose of a unit test is to determine if a feature being tested is fit for use in other parts of an application.
• It is considered best practice to test every method in an application with at least 2 sets of arguments.
• Tests are typically expressed as a combination of three clauses:
  • Given some context
  • When some action is carried out
  • Then consequences should be observable

Example

// Given
String name = "Leon";
Integer age = 25;
Person leon = new Person(name, age);

// When
String getNameResult = leon.getName();
Integer getAgeResult = leon.getAge();

// Then
Assert.assertEquals(name, getNameResult);
Assert.assertEquals(age, getAgeResult);

What are the three clauses of a test?

Given (some context)

• Given is the section of a unit test method that

  • initializes, instantiates, or sets the value of data to pass to test method.

• Example

// Given
String name = "Leon";
Integer age = 25;
Person leon = new Person(name, age);

When (some action is carried out)

• When is the section of a unit test method that
  • invokes the method under test with the arranged parameters

// When
String getNameResult = leon.getName();
Integer getAgeResult = leon.getAge(); 

Then (consequences should be observable)

• Then is the section of a unit test method that
  • verifies that the method to be tested behaves as expected

// Then
Assert.assertEquals(name, getNameResult);
Assert.assertEquals(age, getAgeResult);