It’s been a while since my last blog post and earlier today I came across a post that started a thought process I just had to write down. This post is based on the blog entry titled ““Testing vs Checking” : ‘Tomato’ vs ‘Tomato’” by Mario Gonzalez of Ortask.
As a quick recap, the gist of Mario’s blog post is to criticize the differentiation James Bach, Michael Bolton and, generally, the people aligned with the context-driven approach to testing make between the terms “testing” and “checking”. He basically goes on to claim the whole differentiation is a moot point or even potentially harmful to the testing community, and its future, as a whole (in terms of adding confusion to a field already swamped with definitions). Simplified, but that is my interpretation of the text.
[UPDATE April 8th]: As pointed out by @JariLaakso in Twitter, not all context-driven testers necessarily make the distinction between testing and checking, so I can’t really say “generally, the people aligned with…” as I am not aware of the exact number of people who actually do. I may have simply just communicated with people who do make the distinction so reformat that one sentence in your mind to your liking. [END UPDATE]
However, I am not going to go any deeper into that or any of the other problems I perceived while reading through the post, at least not for now – I’m sure other people will. Instead, I will concentrate on the one thing that bothered me the most at the time of reading it: Mario’s definition of a test. So I decided to dissect it. Here is the definition he offered:
a test attempts to prove something about a system
First of all, that is not even a definition of a test – it is a definition of the purpose of a test. Let me clarify with an analogy. Consider this for a definition of a car:
A car is used to transport people and goods from one place to another
Now, based on that “definition” alone, answer me the following questions:
- What does a car look like?
- What principles and mechanisms does a car operate on?
- Under what conditions and circumstances can a car be used to transport people and goods from one place to another?
You can’t, can you? That’s because I haven’t given you a definition of a car – only what it’s typically used for. In other words:
Defining what an object does does not define what the object is.
While still lacking and incomplete, a definition of a car could be something like: “A car is a typically four-wheeled, land-based vehicle that usually operates on the principle of an internal combustion engine turning the energy contained within a liquid fuel into mechanical movement through a series of controlled explosions the pressure of which cause a crankshaft to rotate and apply torque to the vehicle’s drive wheels”.
While the non sequitur I pointed out above would be reason enough to stop going any further, I want to go through the definition (of the purpose of a test) for the sake of completeness:
- “A test” – Now what is that? In this context the question is impossible to answer – Mario hasn’t told us!
- “attempts” – How does “a test” attempt anything? It’s not a sentient being. It would seem to me it is the tester who is the one to make the attempt through performing a test, making observations, analyzing and interpreting data, behavior and results before, during and after performing a test.
- “to prove” – What, exactly, constitutes proof? Here are some definitions of the term:
Now, how does one arrive at “proof”, based on the above definitions? An obvious problem that immediately comes to mind is that, in many cases, “truths” or “facts” are relative and dependent on a number of factors. Don’t believe me? Well, this is the last sentence in this blog entry. True at the time of writing, but false only seconds later when I kept going.
Also, if you want to pursue the scientific angle, I don’t think anyone would take the result of a single experiment as any kind of proof of anything. You would need to repeat the experiment multiple times (and, ideally, have an independent peer group do the same) in order for it to gain any kind of credibility but therein lies a problem: the conditions would need to be exactly the same every time and that is virtually impossible to achieve in software testing. The date and time change, the amount of available CPU power, RAM and hard disk space varies, there might be network congestion or packet loss that you can not possibly predict, another application might suddenly misbehave and distort your test results or any number of other, unknown, factors that can affect the outcome of a test could manifest themselves.
It would seem to me that “proof” is much too strong a word to use in this context. Testing may suggest behavior that appears consistent but it can not prove that any more than a turkey being generously fed on a daily basis can predict that on the 180th day of its life the farmer comes out with an axe instead of seeds and takes the turkey’s life instead of feeding it.
On with the definition:
- “something” – Anything? Well, Mario did elaborate on this in the following paragraph so I’ll just leave it at that.
- “about a system” – Now there’s another interesting word: “system”. Various definitions to follow:
- 1 a set of things working together as parts of a mechanism or an interconnecting network; a complex whole, or
- 2 a set of principles or procedures according to which something is done; an organized scheme or method (Oxford dictionaries)
- a group of devices or artificial objects or an organization forming a network especially for distributing something or serving a common purpose (Merriam-Webster)
- a set of interacting or interdependent components forming an integrated whole or a set of elements (often called ‘components’) and relationships which are different from relationships of the set or its elements to other elements or sets (Wikipedia)
Complexity. On multiple levels. Especially when talking about computers and software. What if there is a fault in the hardware such that it exhibits certain behavior at one time but a different behavior at other times? Maybe a capacitor is nearing the end of its life and causes a test to give different results based on the ambient temperature of the environment in which the system resides. How many are prepared to, or even capable of, anticipating and accounting for something like that?
I’m not even trying to be funny here – my stereo amplifier does this and for exactly that reason!
Based on all of the above, I’m afraid I can only arrive at the conclusion that this particular definition of a test is fundamentally flawed (even starting from the fact that the claim of what is being defined is unrelated with the actual definition presented) and, in my view, would warrant serious reconsideration and refining.