Communicative testing

A couple of weeks ago I proposed that tests could be thought of as facts that have to be 'explained' by code. In a comment on that post, p.j. hartlieb pointed out that this paradigm relies high tests dependability. And @hlangeveld suggested that test runs should be seen as analogous to experiments.

p.j. hartlieb and @hlangeveld help drive home the point that the purpose of tests is to provide information. If your tests aren't telling you anything, they're useless.

Normative tests

Test runs tell you whether you've finished new features and if you've broken old ones. I would call that normative information, because it reports on conformance to requirements. That kind of knowledge can answer questions like "Is this change ready to commit?" or "Can we go live on Monday?".

Management love normative information because it helps them make decisions and measure progress. This naturally leads to an over-emphasis on tests' role as a source of normative information.

Informative tests

Good tests are also be informative. They explain the meaning of failures and communicate intent. Tests can serve as alternative requirements documentation. Indeed, systems like Fitnesse unify the two concepts by converting requirements into executable acceptance tests.

The audience for informative tests is almost exclusively the development team. Informative tests provide an intimate perspective on the system's concepts that's necessary to work with the software on a daily basis. This is not information required by management, so the impetus to improve the tests' informative qualities needs to come from the development team themselves.

A Selenium system test that reports failure by dumping a raw exception stacktrace serves its normative function perfectly well. There has been a regression. We are not ready to release. Someone tell management so that they can manage the client's expectations. From Issue 658 in the Selenium bug tracker:

org.openqa.selenium.ElementNotVisibleException: Element is not currently visible and so may not be clicked
System info: os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.6.1', java.version: '1.6.0_15'
Driver info: driver.version: remote
 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
 at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
 at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
 at org.openqa.selenium.remote.ErrorHandler.throwIfResponseFailed(ErrorHandler.java:94)
 at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:327)
 at org.openqa.selenium.firefox.FirefoxDriver.execute(FirefoxDriver.java:191)
 at org.openqa.selenium.remote.RemoteWebElement.execute(RemoteWebElement.java:186)
 at org.openqa.selenium.remote.RemoteWebElement.click(RemoteWebElement.java:55)
 at org.openqa.selenium.internal.seleniumemulation.Click.handleSeleneseCommand(Click.java:33)
 at org.openqa.selenium.internal.seleniumemulation.Click.handleSeleneseCommand(Click.java:23)
 at org.openqa.selenium.internal.seleniumemulation.SeleneseCommand.apply(SeleneseCommand.java:30)
 at org.openqa.selenium.WebDriverCommandProcessor$1.call(WebDriverCommandProcessor.java:271)
 at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
 at java.util.concurrent.FutureTask.run(FutureTask.java:138)
 at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
 at java.lang.Thread.run(Thread.java:637)

If this was all that appeared in your test log, it would be very difficult to interpret the failure. There is no context. It's not apparent what functionality the user has lost, whether the error was handled gracefully or even if the problem is a conflict between user stories.

One way to make the result above more informative would be to catch the exception and log a message like "Error when an administrator attempted to reactivate a blocked account". Product owners don't care about the presence of divs. They care about functionality.

Communicative tests

Testing consumes a lot of effort. The return for that investment is readily available information on the state of the software. The more useful and accessible that information is, the more valuable the tests are.

Donald Knuth's description of literate programming is even more pertinent to testers than other programmers because the only purpose of tests is "explaining to human beings what we want a computer to do."

Blunt quantitative statements are sufficient to communicate normative information to people outside the development team. But to fulfill their potential within the team, test results must be qualitative, explanatory and communicative.

Literate programming

The title of this blog is a reference to literate programming, a software development methodology founded by Donald Knuth. Literate programming is best described in Knuth's own words:

Let us change our traditional attitude to the construction of programs: Instead of imagining that our main task is to instruct a computer what to do, let us concentrate rather on explaining to human beings what we want a computer to do.

The practitioner of literate programming can be regarded as an essayist, whose main concern is with exposition and excellence of style. Such an author, with thesaurus in hand, chooses the names of variables carefully and explains what each variable means. He or she strives for a program that is comprehensible because its concepts have been introduced in an order that is best for human understanding, using a mixture of formal and informal methods that reinforce each other.

- Donald Knuth, "Literate Programming" (1984)

I have great affinity for this way of viewing software development. Software design has more in common with the composition of an essay than any strictly scientific activity. I think it's an accident of history that programming is placed within engineering faculties rather than being understood as an outgrowth of philosophy and formal logic.

Literate programming acknowledges software development's place among the humanities. By extension, it acknowledges the relevence of non-scientific ideas to the process of cutting code. Our craft requires the creative and disciplined presentation of thought, so we would be foolhardy to ignore thousands of years of the history of ideas. Programming does not exist inside a vaccuum. Neither should the programmer.

I am not trying to argue that programmers do not need a firm grasp of science. But good programmers cannot rely solely on scientific concepts if they wish their code to be comprehensible to their peers (or future selves).

In the spirit of literate programming I will use this blog to explore software development and its interplay with literature, philosophy, politics and mathematics.