1. Test-driven development
Advanced Software Engineering
Dr Nuha El-Khalili

2. Test-driven development
Design
Code
Test
TDD isn’t about testing...
...it’s about programming!
Traditional development cycle
Test- driven development cycle
Test
Code
Design

3. Test-driven development
Create automated unit tests that define code requirements before writing the code itself
Tests contain assertions that are either true or false.
It makes the developer focus on the requirements before writing the code

4. Test-driven development

5. Test-driven development
Always start with a failing test
Quickly write the simplest code needed to pass the test
Remove duplication or clean up (Refactor)
Repeat as needed to meet requirements
Test everything that could possibly break

6. What can be tested? Valid inputs Invalid inputs
Errors, exceptions, and events
Boundary conditions
Everything that could possibly break!

7. Benefits Code is written for testability
Ensures that tests for every feature will be written
Implement code in small steps
Revert code to the last version that passed all tests
Better code, in less time, with no defects

8. Benefits More modularized code with loose coupling
More maintainable code!
Replace neighbors with mocks

9. But You still need integration testing and acceptance testing.
Badly written test cases will waste the effort of TDD

10. TDD vs Unit testing
A Unit Test is a test of a small functional piece of code
Programmers do unit testing, but:
Not structured
Not Repeatable
Not on all your code

11. Demo Download “test driven” http://www.testdriven.net/ Supports:
Unit Testing Add-In for Microsoft Visual Studio
Supports:
Nunit
Ncover

12. Demo Steps Open new project
Go to the solution explorer and Add a project to the existing solution called Exampletest that has the "class library" type
Go to Add references: open a dialog, go to browse tab go to Nunit folder and choose the units folder and choose the dll file inside that folder
In the ExampleTest class add "import Nunit.framework"

13. Demo Steps
Now create another normal class and add a function there that adds two numbers, do not implement the function.
Go back to the exampleTest class and add a reference to the project
Add "import ProjectName“
Create a test
Create a method call Assert.areequal (10, add(4,6))

14. Demo Steps Right click on the test and choose run.
Test results are down at the bottom window
Test should fail
Implement the function and re-test

15. See it on YouTube