In a presentation titled Skilled Testers and Their Enemies, James Bach identifies the steps involved in skilled bug investigation:



The following post is part of a 13-part series illustrating those points using A Study in Scarlet by Arthur Conan Doyle.

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Examine symptoms of the problem w/o disturbing system state

Holmes examined the room at No. 3, Lauriston Gardens:

“As he spoke, he whipped a tape measure and a large round magnifying glass from his pocket. With these two implements he trotted noiselessly about the room, sometimes stopping, occasionally kneeling, and once lying flat upon his face. So engrossed was he with his occupation that he appeared to have forgotten our presence, for he chattered away to himself under his breath the whole time, keeping up a running fire of exclamations, groans, whistles, and little cries suggestive of encouragement and of hope. As I watched him I was irresistibly reminded of a pure-blooded, well-trained foxhound, as it dashes backward and forward through the covert, whining in its eagerness, until it comes across the lost scent. For twenty minutes or more he continued his researches, measuring with the most exact care the distance between marks which were entirely invisible to me, and occasionally applying his tape to the walls in an equally incomprehensible manner. In one place he gathered up very carefully a little pile of gray dust from the floor, and packed it away in an envelope. Finally he examined with his glass the word upon the wall, going over every letter of it with the most minute exactness. This done, he appeared to be satisfied, for he replaced his tape and his glass in his pocket.”

and the body:

“As he spoke, his nimble fingers were flying here, there, and everywhere, feeling, pressing, unbuttoning, examining, while his eyes wore the same far-away expression which I have already remarked upon. So swiftly was the examination made, that one would hardly have guessed the minuteness with which it was conducted. Finally, he sniffed the dead man’s lips, and then glanced at the soles of his patent leather boots."

In a presentation titled Skilled Testers and Their Enemies, James Bach identifies the steps involved in skilled bug investigation:



The following post is part of a 13-part series illustrating those points using A Study in Scarlet by Arthur Conan Doyle.

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Recall what you were doing just prior to the problem

Just before the problem statement, Holmes was examining the path leading up to the house:

“I had imagined that Sherlock Holmes would at once have hurried into the house and plunged into a study of the mystery. Nothing appeared to be further from his intention. With an air of nonchalance which, under the circumstances, seemed to me to border upon affectation, he lounged up and down the pavement, and gazed vacantly at the ground, the sky, the opposite houses and the line of railings. Having finished his scrutiny, he proceeded slowly down the path, or rather down the fringe of grass which flanked the path, keeping his eyes riveted upon the ground. Twice he stopped, and once I saw him smile, and heard him utter an exclamation of satisfaction. There were many marks of footsteps upon the wet clayey soil; but since the police had been coming and going over it, I was unable to see how my companion could hope to learn anything from it. Still I had had such extraordinary evidence of the quickness of his perceptive faculties, that I had no doubt that he could see a great deal which was hidden from me.”

This examination yielded:

“The very first thing which I observed on arriving there was that a cab had made two ruts with its wheels close to the curb. Now, up to last night, we have had no rain for a week, so that those wheels which left such a deep impression must have been there during the night. There were the marks of the horse’s hoofs, too, the outline of one of which was far more clearly cut than that of the other three, showing that that was a new shoe. Since the cab was there after the rain began, and was not there at any time during the morning — I have Gregson’s word for that — it follows that it must have been there during the night, and therefore, that it brought those two individuals to the house.”

and:

“I’ll tell you one other thing, patent-leathers and Square-toes came in the same cab, and they walked down the pathway together as friendly as possible — arm-in-arm, in all probability. When they got inside, they walked up and down the room — or rather, Patent-leathers stood still while Square-toes walked up and down. I could read all that in the dust; and I could read that as he walked he grew more and more excited. That is shown by the increased length of his strides. He was talking all the while, and working himself up, no doubt, into a fury. Then the tragedy occurred.”

In a presentation titled Skilled Testers and Their Enemies, James Bach identifies the steps involved in skilled bug investigation:



The following post is part of a 13-part series illustrating those points using A Study in Scarlet by Arthur Conan Doyle.

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Notice a problem

The problem is identified at No. 3, Lauriston Gardens:

“At present my attention was centred upon the single, grim, motionless figure which lay stretched upon the boards, with vacant, sightless eyes staring up at the discoloured ceiling. It was that of a man about forty-three or forty-four years of age, middle-sized, broad-shouldered, with crisp curling black hair, and a short, stubbly beard. He was dressed in a heavy broadcloth frock coat and waistcoat, with light-coloured trousers, and immaculate collar and cuffs. A top hat, well brushed and trim, was placed upon the floor beside him. His hands were clenched and his arms thrown abroad, while his lower limbs were interlocked, as though his death struggle had been a grievous one. On his rigid face there stood an expression of horror, and, as it seemed to me, of hatred, such as I have never seen upon human features. This malignant and terrible contortion, combined with the low forehead, blunt nose, and prognathous jaw, gave the dead man a singularly simious and ape-like appearance, which was increased by his writhing, unnatural posture. I have seen death in many forms, but never has it appeared to me in a more fearsome aspect than in that dark, grimy apartment, which looked out upon one of the main arteries of suburban London.”