Domain Testing: Divide and Conquer - Testing Education

o Help (? Key)
• All of the subjects identified the first 6 variables. None of them considered Help. None
identified any other variables.
Input or Output: The first six variables are both input and output variables. On the input side,
you enter or select a value (that's the input). On the output side, the value of the variable controls
how the program displays and prints slides.
• All of the subjects identified these six variables as input variables or they made no explicit
identification and then treated the variables (in the equivalence class table) as input
variables.
• Only 2 subjects, JLT11S4 and JL1418S2, explicitly identified any variables as output.
Neither of these actually analyzed the output variables. Their equivalence class table dealt
only with the input-related issues for these variables. One additional subject, JL28A1S4,
mentioned output tests (for example, s/he said of # of slides that an error could be failure
to print the slides correctly) but s/he listed all variables only as input variables and s/he
didn't explore the output-related risks in any detail.
• If I put the "width" variable in front of 10 experienced testers, especially if I asked them to
identify output variables, I would expect several, perhaps all, to deal with at least one or
two output dimensions associated with this variable. I interpret the subjects' failure to
consider the output issues involved with these variables as partially due to their
inexperience and partially due to negative transfer from a course that focused primarily on
analysis of input variables.
Dimensions: The question is, what should we vary to test this variable?
Here's an example:
• Slides Sized For
o It is both an input and an output variable. You select a value (input) but that value
controls how the program displays and prints slides. If you change this with an
existing presentation, you may change the font size of the existing slides.
o Has only two obvious dimensions, as an input variable. One dimension is the
enumerated list. The other is the side effect impact on the other variables (height,
width, etc.) As an output variable, it changes a lot of things, such as default font
size, the font sizes of existing text, the default scaling of the slide on the screen,
the ability of the attached printer to print the slide.
• To test the input variable, one obvious dimension involves the value that the program
appears to be requesting. Examples:
o the Slides Sized For variable is enumerated. One "dimension" is the set of all
values in the enumerated list.
o the Width variable is floating point. The dimension runs from smaller Widths to
larger Widths. It appears to run from 1 to 56 inches.
• There are other aspects of the input variable that are orthogonal to the identified
dimension. For example, for the width: