Common Mechanisms of UML

Testing Blindness

Testing Blindness is a pathological (harmful)situation in which the desired path is achieved for the wrong reason
There are three types of testing blindness

 

Assignment Blindness
Assignment Blindness occurs when the buggy predicate appears to work correctly because the specific value chosen for an assignment statement works with both the correct and incorrect predicate
Example:

Correct X = 7 ------- if Y > 0 then

Buggy X = 7 ------- if X + Y > 0 then..

If the test case sets Y = 1, the desired path is taken in either case, but the bug still exists

Equality Blindness
Equality Blindness occurs when the path selected by prior predicate results in a value, that works both for the correct and buggy predicate
Example:

Correct If Y = 2 then ----------- If  X + Y > 3 then

Buggy If Y = 2 then ----------- If X > 1 then

The first predicate, if y = 2 forces the rest of the path, so that for any positive value of x, the path taken at the second predicate will be the same for the correct and buggy version

Self Blindness
Self blindness occurs when the buggy predicate is a multiple of the correct predicate, and as a result is indistinguishable along that path
Example:

Correct X = A ------- if X – 1 > 0 then

Buggy X = A ------- if X + A + 2 > 0 then..

The assignment (x =a) makes the predicates multiples of each other, so the direction taken is the same for the correct and buggy version