1. The Effectiveness of Test-first Programming
By Shawn Morgan
Greet yourself, and say that you’ll be presenting on Test-first programming.

2. Test-driven Development Test-first Programming Test-last Programming
TDD Hierarchy
Test-driven Development
(TDD)
Test-first Programming
(TFP)
We all know about test-driven development (TDD), read an article on it and lecture. As the hierarchy shows, TFP goes head-to-head with TLP. We’ll be comparing the two over the course of the presentation.
Test-last Programming
(TLP)

3. What’s TFP? Purpose Process Test-before-implementation
Create test based on some functionality
Implement code to pass test
Run test and verify the code
TFP is when you write up a functional test based on some set requirements, implement the code, and then run the test to verify the code works as expected.

4. Background Previous studies
The authors of the article this presentation is based on show previous studies that took place before the article was written, with the article’s study being in the last row.

5. Background Previous studies
Three professors conducted a case study using test-driven development, and found that writing tests improved code quality without any cost to productivity. Notice how the focus was not test-first.

6. Background Previous studies
Later on, a more controlled study took place where the same approach was taken, but the authors found that productivity had declined as a result. Notice again how they went with the test-last approach.

7. Background Previous studies
The article’s study, on the other hand, has the programmers writing the tests first. This approach produced the best results, and you can see the difference here.

8. Article’s Experiment Two groups: Compare test-first vs test-last
Control Group – test-last programming
Experiment Group – test-first programming
Compare test-first vs test-last
Hypothesis
Gather data
Theory
So in the article’s experiment two groups participated to represent each approach. The control group would create their code first, while the experiment group would create their tests first. We’ll see the hypothesis made, the data that was gathered, and the resulting theory.

9. 2-Stage Null Hypothesis
The hypothesis created was divided into two stages.

10. Stage 1
In the first stage, they think that test-driven development alone will improve quality and productivity.

11. Stage 2
In stage 2, they think that, for each test that is produced…

12. Stage 2
…quality and productivity will be increased even more, since testing enhances task focus, ergo enhancing both of the factors. Since test-first programming forces test creation rather than test-last, we should expect better results than in TLP.

13. 2-Stage Hypothesis

14. Story Comparison TLP TFP
For each typical--what they call– story.. (Left-side, right-side, only talk about the process and not the siginificance).

15. Story Comparison
TLP
TFP

16. Story Comparison
TLP
TFP

17. Worst-case Time Comparison
TLP
TFP
(Left-side, right-side, only walk through how it was done, and—again—don’t mention the significance of anything).

18. Worst-case Time Comparison
TLP
TFP

19. Worst-case Time Comparison
TLP
TFP

20. Worst-case Time Comparison
TLP
TFP

21. Graphical Representation of Results - Quality
This first graph shows the results on how quality varied between TFP and TLP. Variability in quality increased as more tests were made. Notice how TFP didn’t consistently outperform in this area.

22. Graphical Representation of Results - Productivity
(x100%)
For productivity, the authors realized how much better productivity was for TFP.

23. Alternate Hypothesis (Theory)
Modify the hypothesis:
Quality improvement not proportional as expected
Bummer!
Productivity improvement much more noticeable
…but why?
So now they have to modify their hypothesis. They realize that quality improvement was not as expected. On the other hand, improvement in productivity was much more noticeable.
(Put the formulas below for emphasis)

24. Why was Productivity Better?
Productivity was better because of:
Better task understanding
Better task focus
Faster learning
Lower rework effort
They concluded from their data that the task was more understood since the requirements were made clear up front through creating tests, more effort was spent by each task at a time rather than implementing all of them at once, an increase in productivity caused the programmers to understand the tasks more effectively, and reworking tests one by one was much easier than having to fix multiple tests at once.

25. Conclusion Article’s experiment shows TFP can…
Encourage programmers to be more productive
Lessen rework of implemented code
Increase quality of implemented code
Outperforms test-last programming
To sum it all up, TFP…
[Note: Do NOT add citations. This goes to the teacher if he wants them]