Test Driven Development

Introduction

Costs

The cost of software according to this course was Tests are split into three categories

• Does what was asked for
• Responds appropriately to bad input
• Acceptable Performance

Red Green Refactor

Start by writing tests with no code, write until test pass, refactor code. This is an iterative approach.

Benefits

• Requirements are verified by the tests
• Regression issues raised early
• Costs of maintenance is lowered
• Design first, when writing the tests first we are designing what they want
• Reduces over engineering
• Easy to know where you are in the project

Different Types of Testing

Types of Testing

• Unit Testing
• Functional Testing (UI/End-to-End)
• Integrating Testing
• User Acceptance Testing

Testing Approaches

• Black Box testing (testing the interface)
• White Box testing (testing internal aspects)

Tools

Some well known tools are

• Selenium
• Watir
• VS Coded UI
• Test Studio (Telerik)
• Silk Test (Micro Focus)

Terminology

• Test
• Test Suite (Group of tests)
• Before/After hooks to set up and tear down
• Assert, eg. isTrue, isNull, areEqual
• Test Execution
• Test Runner (async/sync)

Example Fizz Buzz

Requirements

This has the following requirements Given a positive number

• Divisible by 3 => "Fizz"
• Divisible by 5 => "Buzz"
• Divisible by 3 & 5 => "Fizz Buzz"
• Otherwise => Number

Step 1

Create initial test

        private FizzBuzzService _fizzBuzzService;

        public FizzBuzzTests() {
            _fizzBuzzService = new FizzBuzzService();
        }

        [TestMethod]
        public void ShouldPrintNumber() {
            Assert.AreEqual("1", _fizzBuzzService.Print(1));
        }

Step 2

So lets build out tests up as we go until we get to.

...
        [TestMethod]
        public void ShouldPrintFizz()
        {
            Assert.AreEqual("Fizz", _fizzBuzz.Print(3));
        }

        [TestMethod]
        public void ShouldPrintBuzz()
        {
            Assert.AreEqual("Buzz", _fizzBuzz.Print(5));
            Assert.AreEqual("Buzz", _fizzBuzz.Print(10));
        }

        [TestMethod]
        public void ShouldPrintFizzBuzz()
        {
            Assert.AreEqual("FizzBuzz", _fizzBuzz.Print(15));
        }
...

Techniques

Dependency Injection

This is used in Frameworks all the time.