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http://www.satisfice.com/blog/archives/58

테스트 자동화에 대한 흥미로운 시각이 있어 소개한다. 참고로 이 분은 Exploratory Testing의 주창자이다.

Manual Tests Cannot Be Automated

I enjoy using tools to support my testing. As a former production coder, automated tests can be a refreshing respite from the relatively imponderable world of product analysis and heuristic test design (I solve sudoku puzzles for the same reason). You know, the first tests I ever wrote were automated. I didn’t even distinguish between automated and manual tests for the first couple of years of my career.

Also for the first six years, or so, I had no way to articulate the role of skill in testing. Looking back, I remember making a lot of notes, reading a lot of books, and having a feeling of struggling to wake up. Not until 1993 did my eyes start to open.

My understanding of cognitive skills of testing and my understanding of test automation are linked, so it was some years before I came to understand what I now propose as the first rule of test automation:

Test Automation Rule #1: A good manual test cannot be automated.

No good manual test has ever been automated, nor ever will be, unless and until the technology to duplicate human brains becomes available. Well, wait, let me check the Wired magazine newsfeed… Nope, still nothing human brain scanner/emulators.

(Please, before you all write comments about the importance and power of automated testing, read a little bit further.)

It is certainly possible to create a powerful and useful automated test. That test, however, will never have been a good manual test. If you then read and hand-execute the code? if you do exactly what it tells you? then congratulations, you will have performed a poor manual test.

Automation rule #1 is based on the fact that humans have the ability to do things, notice things, and analyze things that computers cannot. This is true even of “unskilled” testers. We all know this, but just in case, I sprinkle exercises to demonstrate this fact throughout my testing classes. I give students products to test that have no specifications. They are able to report many interesting bugs in these products without any instructions from me, or any other “programmer.”

A classic approach to process improvement is to dumb down humans to make them behave like machines. This is done because process improvement people generally don’t have the training or inclination to observe, describe, or evaluate what people actually do. Human behavior is frightening to such process specialists, whereas machines are predictable and lawful. Someone more comfortable with machines sees manual tests as just badly written algorithms performed ineptly by suger-carbon blobs wearing contractor badges who drift about like slightly-more-motivated-than-average jellyfish.

Rather than banishing human qualities, another approach to process improvement is to harness them. I train testers to take control of their mental models and devise powerful questions to probe the technology in front of them. This is a process of self-programming. In this way of working, test automation is seen as an extension of the human mind, not a substitute.

A quick image of this paradigm might be the Mars Rover program. Note that the Mars Rovers are completely automated, in the sense that no human is on Mars. Yet they are completely directed by humans. Another example would be a deep sea research submarine. Without the submarine, we couldn’t explore the deep ocean. But without humans, the submarines wouldn’t be exploring at all.

I love test automation, but I rarely approach it by looking at manual tests and asking myself “how can I make the computer do that?” Instead, I ask myself how I can use tools to augment and improve the human testing activity. I also consider what things the computers can do without humans around, but again, that is not automating good manual tests, it is creating something new.

I have seen bad manual tests be automated. This is depressingly common, in my experience. Just let me suggest some corollaries to Rule #1:

Rule #1B: If you can truly automate a manual test, it couldn’t have been a good manual test.

Rule #1C: If you have a great automated test, it’s not the same as the manual test that you believe you were automating.

My fellow sugar blobs, reclaim your heritage and rejoice in your nature. You can conceive of questions; ask them. You are wonderfully distractable creatures; let yourselves be distracted by unexpected bugs. Your fingers are fumbly; press the wrong keys once in while. Your minds have the capacity to notice hundreds of patterns at once; turn the many eyes of your minds toward the computer screen and evaluate what you see.

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