TDD by example

TDD is best understood by looking at examples, so let’s take a story and write it TDD-style. We will be working on the feature described by this story:

Story Title:

Changing a username

Story Description:

As a customer

Given I already have an account

When I navigate to my profile page

Then I can update my username

Acceptance Criteria:

The username can only contain between 8 and 12 characters, inclusive:

- Valid: AnameOf8, NameOfChar12

- Invalid: AnameOfChar13, NameOf7

Only alphanumerics and underscores are allowed:

- Valid: Letter_123

- Invalid: !The_Start, InThe@Middle, WithDollar$, Space 123

If the username already exists, generate an error

Let’s not waste any time and implement this story.

Creating the solution shell

We will create a class library called Uqs.Customer, add a unit testing project to test it called Uqs.Customer.Tests.Unit, and add them to a solution called TddByExample.sln. So, let’...