Test-Driven Development

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The Three Laws of TDD. by Robert Cecil Martin "Uncle Bob" (October 7^th, 2005) ► Robert Cecil Martin "Uncle Bob" defines the TDD process and explains its big advantages.
An Introduction to Test Driven Development in C# by Richard Banks (January 19^th, 2008) ► A quick introduction to TDD using C# and NUnit.
Evolutionary architecture and emergent design: Test-driven design, Part 1 — Allowing tests to drive and improve your design🗑️ by Neal Ford (February 24^th, 2009) ► The author tries to convince that writing tests first results into a better design.
↪Evolutionary architecture and emergent design: Test-driven design, Part 2 — More on allowing tests to drive and improve your design🗑️ by Neal Ford (April 7^th, 2009) ► The continuation of the previous article.
The Transformation Priority Premise by Robert Cecil Martin "Uncle Bob" (December 19^th, 2010) ► Robert Cecil Martin "Uncle Bob" proposes a prioritised list of transformations (giving higher priority to simpler transformations) to be applied when the code must be changed to get the last added test green. Each transformation results in a more generic code. He claims that, by privileging the simplest transformations, the risk of an impasse (i.e. having to rewrite an important part of the production code in order to get the next test green) is reduced.
↪Robert C Martin - The Transformation Priority Premise↑ by Robert Cecil Martin "Uncle Bob" (June 8^th, 2011) ► A speech with the same content as the previous article.
J.B. Rainsberger↑ by J. B. Rainsberger (February 28^th, 2012) ► Another introduction, this one in Java.
MountainWest RubyConf 2013 Trolls of 2013 by Ryan Davis by Ryan Davis (April 4^th, 2013) ► Writing an interpreter in Ruby while using TDD. Ryan Davis finishes with a lightning talk, presenting Flay, a code analysis tool detecting similar code pieces.
Straw Man TDD by Jason Gorman (May 17^th, 2013) ► Refuting some arguments about TDD.
Ian Cooper: TDD, where did it all go wrong↑ by Ian Cooper (June 2013) ► Coming back to the initial ideas of Kent Beck with some good advice on how to do TDD.
Larry and Jen do Roman Numerals in C++ by Jon Jagger and Olve Maudal (July 19^th, 2013) ► An example of C++ TDD.
The Right Tests in the Wrong Order by Mike Jansen (August 18^th, 2013) ► The order of the tests will have an important impact on the final production code. This article does not help determining this order. Its main conclusion if that if too much code must be changed for getting the next test green, the developer should back up and consider another approach.
What Really Matters in Test-Driven Development — It isn't about the tests -- it's about the feedback. by Peter Provost (August 28^th, 2013) ► More than writing tests first, the important point is to have a very short code / test loop.
Test First by Robert Cecil Martin "Uncle Bob" (September 23^rd, 2013) ► Tests should be written first, clean first, maintain first.
The Domain Discontinuity by Robert Cecil Martin "Uncle Bob" (January 14^th, 2014) ► Architecture is an up-front decision and is expensive to change after; code design is driven by the tests and is continuously refactored.
When Should You Think? by Robert Cecil Martin "Uncle Bob" (March 11^th, 2014) ► When to think: before, during and after coding. An answer to those who claim that TDD results into developers not thinking enough.
When TDD doesn't work. by Robert Cecil Martin "Uncle Bob" (April 30^th, 2014) ► TDD cannot be used for the physical boundary and the layer just before it, this one should be as thin as possible, business logic should be moved elsewhere.
Professionalism and TDD (Reprise) by Robert Cecil Martin "Uncle Bob" (May 2^nd, 2014) ► TDD may have the same impact, in the future, on the software industry as washing hands had on medicine.
Test-Driving the Game Loop pt. 1 by Eric Smith (August 18^th, 2014) ► Applying TDD to the classical game loop. This is typical the case where you can wonder if you are testing too much give the simplicity of the production code.
↪Test-Driving the Game Loop pt. 2 by Eric Smith (October 14^th, 2014) ► This is the continuation of the previous blog. Code is getting less trivial, tests are making sense.
Test Time by Robert Cecil Martin "Uncle Bob" (September 3^rd, 2014) ► Robert Cecil Martin "Uncle Bob" explains that tests must be fast and the design should be such to enable this. (This gets back to DHH who explains that design should not be corrupted for the only purpose of getting fast tests.)
Thorns around the Gold by Robert Cecil Martin "Uncle Bob" (November 19^th, 2014) ► Robert Cecil Martin "Uncle Bob" advices to write first tests for exceptional behaviours, then degenerate behaviours, then ancillary behaviours, before testing the core feature.
The Cycles of TDD by Robert Cecil Martin "Uncle Bob" (December 17^th, 2014) ► The coding cycle levels: the three laws of TDD for the seconds cycle, Red/Green/Refactor for the minutes cycle, the specific/generic transform for the 10 minutes cycles, and the Clean Architecture for the hours cycle.
Test-Driven Development is Stupid by Ian Mallett (February 21^st, 2015) ► The guy writes against TDD, he gets some buzz and a lot of hate mails, then he understands he does not know what is TDD.
The MODE-B Imperative by Robert Cecil Martin "Uncle Bob" (February 21^st, 2015) ► Robert Cecil Martin "Uncle Bob" wrote a PDP8 emulator and explains the difference between the very long code / compile / test loop of that time, which required carefulness and deliberateness, and the same loop which must be keep very short today.
An External Replication on the Effects of Test-driven Development Using a Multi-site Blind Analysis Approach by Davide Fucci, Giuseppe Scanniello, Simone Romano, Martin Shepperd, Boyce Sigweni, Fernando Uyaguari, Burak Turhan, Natalia Juristo, and Markku Oivo (September 2016) ► A inconclusive study on the analysis of TDD. But the study conditions (the implementation of a very small piece of software) were probably not adequate to demonstrate something.
↪TDD Doesn't Work by Robert Cecil Martin "Uncle Bob" (November 10^th, 2016) ► Robert Cecil Martin "Uncle Bob" analyses the previous study.
Dijkstra's Algorithm by Robert Cecil Martin "Uncle Bob" (October 26^th, 2016) ► An example of using TDD. The exercise is interesting: the whole algorithm is done in a single final step…
TDD Lesson - Terrain Generation by Robert Cecil Martin "Uncle Bob" (January 9^th, 2017) ► Writing unit tests spying the actions of the production code.
Symmetry Breaking by Robert Cecil Martin "Uncle Bob" (March 7^th, 2017) ► The analogy between TDD and accounting, and the difference due to the fact that, contrarily to credit / debit, production code / test code cannot be written in any order, test must be written first.
What I’m talking about when I talk about TDD by Uberto Barbini (August 25^th, 2017) ► TDD allows the author to test different designs without having to keep in mind all the details during that time.
Excuses by Robert Cecil Martin "Uncle Bob" (December 18^th, 2017) ► There is nothing new in this blog which describes once again the analogy between TDD and accounting, and tries to use it to kill the anti-TDD arguments.
Five Underplayed Premises Of TDD by Mike Hill (January 17^th, 2018) ► The title says it all, but these basis ideas are applicable to software development in general, they are not specific to TDD.
↪The Citizenship Argument by Robert Cecil Martin "Uncle Bob" (January 18^th, 2018) ► Some comments about the previous video, but this is the usual rant about TDD and good citizenship.
TDD ça ralentit ? Regarde ça, tu vas changer d'avis !↓ by Michaël Azerhad (July 3^rd, 2018) ► A demo of TDD on the look-and-say sequence, but the final code is not clean (in my opinion).
When Test Driven Development Goes Wrong • Dave Farley • GOTO 2021 by Dave Farley (May 7^th, 2021) ► Some examples of tests which have been very badly driven, because the code is badly designed.
Test-Driven Development Is Still Alive and Well — But TDD might not be the right fit for every developer. by Tammy Xu (October 5^th, 2021) ► A usual summary of the benefits of TDD reported by some persons praticing it.
The 3 Types of Unit Test in TDD • Dave Farley • GOTO 2022 by Dave Farley (December 2^nd, 2022) ► Test returned value vs. test state change vs. test interaction with another component (with a description of stub, fake, spy, and mock).
TDD Isn't Design — It's Design Feedback by Kent Beck (December 7^th, 2023) ► TDD does not generate the design, but provides a way to quickly test an interface design decision without making implementation design decisions.
Canon TDD by Kent Beck (December 11^th, 2023) ► Yet another description of the TDD process.
TDD's Missing Skill: Behavioral Composition by Kent Beck (March 29^th, 2024) ► Applying TDD requires that you are able to split the behaviour of the system into pieces before starting to implement it.
Detroit school vs. London school
- Test Driven Development Wars: Detroit vs London, Classicist vs Mockist by Adrian Booth (October 31^st, 2018) ► A clear but oversimplied description of the two schools.
- London vs Chicago by Doug Klugh (October 17^th, 2019) ► A short list of the advantages and disadvantages of both methods.
- Detroit and London Schools of Test-Driven Development↑ by Maciej Falski (June 8^th, 2020) ► A long analysis of the two styles of TDD.
- TDD : Inside Out, Outside In, démêlons le sujet by Nicolas Le Borgne (February 11^th, 2021) ► This article is a not-so-clear summary of what is commonly said about the two schools.
- Are You Chicago Or London When It Comes To TDD? by Dave Farley (September 14^th, 2022) ► A description of the two schools.
Brett L. Schuchert
- RPN calculator in Java using Eclipse
  - Getting Started with Tdd in Java using Eclipse by Brett L. Schuchert (March 30^th, 2010) ► A rather slow but clear introduction to TDD using Java and Eclipse: creating a RPN calculator.
  - ↪Adding Basic Operators to the RpnCalcualtor by Brett L. Schuchert (March 30^th, 2010) ► Adding add, subtract and factorial to the previous example.
  - ↪Removing Duplication and the Ocp by Brett L. Schuchert (March 31^st, 2010) ► Modifying the API of the previously implemented operators.
  - ↪Extracting to strategy by Brett L. Schuchert (March 31^st, 2010) ► Implementing the Strategy pattern.
  - ↪Removing Duplication by Refactoring by Brett L. Schuchert (April 2^nd, 2010) ► Factoring common code into a base class and adding multiply.
  - ↪Removing Duplication Via TDD using Mockito by Brett L. Schuchert (April 2^nd, 2010) ► Using Mockito, a mocking framework.
  - ↪Introducing an Abstract Factory by Brett L. Schuchert (April 2^nd, 2010) ► Explaining how to use dependency injection to be able to mock a class.
  - ↪Adding a Sum Operator by Brett L. Schuchert (April 4^th, 2010) ► Using what has been done previously to add a sum operator.
  - ↪Adding a Prime Factors Operator by Brett L. Schuchert (April 4^th, 2010) ► Using human readable (kind of BDD) test naming.
  - ↪Composing Math Operators and Programming the Calculator by Brett L. Schuchert (April 4^th, 2010) ► An implementation of the composite pattern, but this does not teach new things about writing Unit Tests.
  - ↪Using FitNesse to Program The Calculator by Brett L. Schuchert (April 4^th, 2010) ► A short demonstration on how to download, install, and write the fixtures for FitNesse.
- Shunting Yard Algorithm in C# using Visual Studio and ReSharper
  - Shunting Yard Algorithm in C#, Part 1 by Brett L. Schuchert (April 15^th, 2010) ► A demonstration on using TDD in Visual Studio. The pace is quite fast.
  - ↪Shunting Yard Algorithm in C#, Part 2 by Brett L. Schuchert (April 15^th, 2010) ► Implementation of operator precedence.
  - ↪Shunting Yard Algorithm in C#, Part 3 by Brett L. Schuchert (April 15^th, 2010) ► Implementation of parentheses. The design is dubious and the way he adds division support is even more hacky: he does not add a simple test for this one.
  - ↪Shunting Yard Algorithm in C#, Part 4 by Brett L. Schuchert (April 15^th, 2010) ► Managing functions.
  - Removing Duplicate Operator Representation, (part 6 of 4) by Brett L. Schuchert (April 16^th, 2010) ► Defining the list of operators at a single place. His usage of regexp is very dubious.
Is TDD dead? (Martin Fowler’s notes)
- TDD is dead. Long live testing. by David Heinemeier Hansson (April 23^rd, 2014) ► TDD has been useful by making developer aware of the need for automated regression testing, but focusing only on fast unit tests appears now not as the best way to test software and make the design overly complex.
- Test-induced design damage by David Heinemeier Hansson (April 29^th, 2014) ► Changing the design in order to unit test all layers is damaging it.
- ↪Test Induced Design Damage? by Robert Cecil Martin "Uncle Bob" (May 1^st, 2014) ► An answer to the previous blog: separation of concerns is a good thing.
- Is TDD dead? by David Heinemeier Hansson, Kent Beck, and Martin Fowler (May 9^th, 2014) ► TDD is more or less adequate, depending on the developer, depending on the situation. TDD is just one way to get self-testing code.
- ↪Is TDD dead? [Part II] by David Heinemeier Hansson, Kent Beck, and Martin Fowler (May 16^th, 2014) ► Is (too much) decoupling bad design? Is bad design due to TDD?
- ↪TW Hangouts | Is TDD dead? [Part III] by David Heinemeier Hansson, Kent Beck, and Martin Fowler (May 20^th, 2014) ► The tradeoffs of testing:
  - Instant feedback is not possible, how much frequent should be the feedback we need?
  - How accurate/fidelitous should be the tests?
  - Lifespan? For how long will the software be used? With which probability?
  Feedback is not only about knowing if the users are satisfied by the new feature, but also to know if there are some regressions with previously existing features and if the code base is still healthy.
  TDD gave overconfidence to developers, they thought they could deliver quality software without someone else, such as a QA team, looking at it. TDD focused only on the test speed, without looking at what is traded of. Listening to feedback of real users is necessary, believing that the quality is good because all tests are green and the testing code coverage is 100% is an error.
- ↪TW Hangouts | Is TDD dead? [Part IV] by David Heinemeier Hansson, Kent Beck, and Martin Fowler (May 27^th, 2014) ► How much test is required? TDD advocates tend to say that tests are more important than the production code, this leads to refactoring being neglected.
- ↪TW Hangouts | Is TDD dead? [Part V & VI] by David Heinemeier Hansson, Kent Beck, and Martin Fowler (June 4^th, 2014) ► Answering some questions (examples of open-source projects where TDD was successful or a failure, is there a way to write software so TDD would be redundant, TDD and inexperienced developers…) and concluding the debate.
- First by Robert Cecil Martin "Uncle Bob" (May 19^th, 2014) ► Robert Cecil Martin "Uncle Bob" tries to participate to the "Is TDD dead?" debate. Tests provide some up-to-date documentation, force some decoupling in the design, and give confidence to change the code. They are so important that they must be done first.
- Is TDD Dead? Final Thoughts about Teams. by Robert Cecil Martin "Uncle Bob" (June 17^th, 2014) ► TDD is a team practice, not an individual choice. Robert Cecil Martin "Uncle Bob" predicts that teams, then companies, will choose between TDD and non-TDD, and the first ones will win.
- Pecha Kucha @ OOP 2015 "Is TDD dead?" von Uncle Bob by Robert Cecil Martin "Uncle Bob" (January 30^th, 2015) ► Robert Cecil Martin "Uncle Bob" is still upset to not having been invited to the discussion.
- TDD Harms Architecture by Robert Cecil Martin "Uncle Bob" (March 3^rd, 2017) ► A more constructive answer to the fact that TDD generates bad design: the design is defined by the developer, not by TDD.
Discovery Testing the Game of Life
- Discovery Testing the Game of Life (Part 1) by Justin Searls (September 9^th, 2015) ► A high-level presentation of the differences between Detroit-school TDD and London-school TDD.
- ↪Discovery Testing the Game of Life (Part 2) by Justin Searls (September 9^th, 2015) ► Coding the high level of the application.
- ↪Discovery Testing the Game of Life (Part 3)↓ by Justin Searls (September 10^th, 2015) ► The continuation of the development is getting very painful.
- ↪Discovery Testing the Game of Life (Part 4)↓ by Justin Searls (September 10^th, 2015) ► … and we get an application which is far from being finished, is overly complex (a bunch of small simple classes), and much slower and memory consumming than necessary. A pragmatic implementation of the game of life would be simpler, faster and use less memory. This series is just the proof that TDD can result in a stupid implementation.