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Quick Intro

Lecture 1 - A Bug or Not a Bug -> Quick Intro -> Three Conditions Of A Bug’s Existence

According to the logical law, each item is either P or not-P. There are no other alternatives; i.e., if you have Rolex watch #F787999, any object in universe will be:

– EITHER your Rolex #F787999

– OR not

Imagine that you stand at the end of an assembly line where certain objects come toward you one by one. Your task is simple: to expect the appearance of your Rolex #F787999 and confidently call out “BUG!” if anything else shows up.


– a pack of buttermilk

– an electronic alarm clock

– Rolex #F787998

anything else except our Rolex #F787999 will be labeled a “bug.”

Now, let’s find similarities in the following three situations:

            1. Your new girlfriend claims that she is a great chef and in the morning she cannot even make a piece of toast.

            2. You are reading a book on software testing and it tells you about toast making.

            3. Your girlfriend from #1 has read the book from #2, but the toast is burnt to a crisp.

All these situations are similar because each of them has a mismatch between the actual result and the expected result.


            Expected result: girlfriend knows how to cook

            Actual result: morning without toast


            Expected result: talk about software testing

            Actual result: talk about a girlfriend and making toast in the morning


            Expected result: toast is finally made

            Actual result: another toastless morning

Here is the definition of a “bug”:

A bug is a deviation of an actual result from an expected result. 

According to the logical law of the excluded middle, we have a bug in ANY case where an actual result deviates from an expected result. Next ->

Lecture 1 - A Bug or Not a Bug -> Quick Intro -> Three Conditions Of A Bug’s Existence