On the Effectiveness of the Test-First Approach to Programming
Method
"The experiment was conducted with undergraduate students. While the experiment group applied a test-first strategy, the control group applied a more conventional development technique, writing tests after the implementation."
Population
"Thirty-five subjects participated in the study... we retained data from 24 subjects. Eleven of those subjects were in the Test-First (TF) group and 13 in the Test-Last (TL) group."
What it does not show
Students, one small task, 30% attrition. Critically for this site: it tests test-order in greenfield feature work, NOT the narrower practice of reproducing a reported bug in a failing test before fixing it. It is adjacent evidence about TDD generally, not direct evidence about bug-reproduction-first.
Hakan Erdogmus, Maurizio Morisio, Marco Torchiano
Test-first students wrote more tests, and writing more tests predicted higher productivity. On quality — the benefit most often claimed — the result was null: “there are no significant quality differences between the two groups”, with the test-last group’s median quality numerically higher.
Tier I: Genuine controlled experiment with assignment to test-first and test-last groups; undergraduate subjects on one small task, which limits external validity but not the design.