Skilled Bug Investigation Illustrated - Recall what you were doing

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.

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.”

“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.”