What is the first published reference to test-first programming?

Question

I am rereading Refactoring by Martin Fowler. In Chapter 4, Building Tests, I came across the following passage.

In fact, one of the most usefull times to write tests is before you start programming. When you need to add a feature, begin by writing the test. This isn't as backward as it sounds. By writing the test you are asking yourself what needs to be done to add the function. Writing the test also concentrates on the interface rather than the implementation (always a good thing). It also means you have a clear point at which you are done coding--when the test works.

While I am an advocate of test-driven development now, I did not remember having been introduced to the concept when I originally read this book nearly 5 years ago.

According to Amazon.com, this book was originally published on July 8, 1999. Is this the first published reference to test-first programming or is there something even earlier?

Answer 1

Jon Bently in Programming Pearls (originaly published 1986) does not specifically mention Test-First programming. But in the chapter "Writing Correct Programs", he describes writing an algorithm by first defining the preconditions, invariants and postconditions, and in the next chapter describes an automated testing framework.

It's not quite test-first, but he was definitely laying some of the groundwork.

Also,

CIO Magazine, March 1993, Bug Busters, by Lucie Juneau, pg 84:

Test cases ... can be developed even before any code has been written. Ideally these cases are based on an application's requirements ... If developers are given requirements-based tests before they begin to write code, they will design a product that can pass those tests ... "

Answer 2

Test driven development is similar to design by contract, where you have preconditions, invariants and postconditions.

The term was coined by Bertrand Meyer in connection with his design of the Eiffel programming language and first described in various articles starting in 1986 [Wikipedia]

Formal methods date from at least 1983, and have been used for safety critical systems such as the driverless Paris metro using the B-method:

In the first and the most abstract version, which is called Abstract Machine, designer should specify the goal of the design. [Wikipedia]

These could be some of the things from which Kent Beck "helped pioneer... the rediscovery of test-first programming".

More to the point: Apparently Nasa's early 1960s Project Mercury was the first software project using test-driven development and other agile practices. I couldn't find any early documentation, but here's a 2003 report that quotes project members' communication:

Project Mercury ran with very short (half-day) iterations that were time boxed. The development team conducted a technical review of all changes, and, interestingly, applied the Extreme Programming practice of test-first development, planning and writing tests before each micro-increment.

The rest of the report is interesting too, it goes on to say:

The earliest reference we found that specifically focused on describing and recommending iterative development was a 1968 report from Brian Randell and F.W. Zurcher at the IBM T.J. Watson Research.

In addition to automated testing, the 1968 report advocates parallel coding and testing, if not test-first:

g. Detail design, coding and documentation of each program block.
h. Design and documentation of test methods for each program block in parallel with step (g).

Answer 3

That was Kent Beck, in his book Extreme Programming, also published in 1999.