Multi - Generating test ideas from expressions with booleans and relational operators

A test idea is a brief statement of something that should be tested. For example, if you're testing a square root function, one idea for a test would be "test a number less than zero". The idea is to check if the code handles an error case.

Test ideas are gotten in a number of ways. This program helps derive test ideas from expressions that contain boolean operators and relational operators. The rationale behind the program is described in my "Testing for Programmers" course notes, beginning with the slide titled "A Program for Finding Faults in Boolean Expressions", currently slide 22.

This program has a primitive command-line interface. Someday I will enter the 80's and put on a GUI. Then I'd enter the 90's and provide an applet interface, except it's the 00's and Java in the browser is going away. Here's what it looks like with the timeless interface:

% multi
Type in an expression.
'q' to quit.
> a && b < c
Test ideas for (a && (b<c)):
       a          (b<c)
   -----   ------------
    true   b barely < c
   FALSE           true
    true           b==c

> q

So, if the expression is inside a function foo(boolean a, int b, int c), these three test inputs might satisfy the test ideas:

• foo(true, 1, 2)
  1 is the integer "just less than" 2.
• foo(false, -1000, 2340333)
  Notice that I used numbers quite different from 1 and 2, just on general principles: variety is good.
• foo(true, 23, 23)

That's pretty much all there is to it.

In this version, there's one major restriction. The expressions cannot contain duplicate names:

> (a && b) || (a && c)
Parse Error: 'a' appears twice in the expression. Duplicates aren't allowed yet.

Installation

Multi is written in Java. Stop now if you don't have Java on your machine.

1. Fetch either the tar archive or the zip archive. Extract the files.
2. You'll see two jar files: Multi.jar and Trace.jar. Put those in your CLASSPATH.
3. Run the program with java com.testing.multi.Multi (The multi script will save you typing.)

After the first person asks, I'll package up the source into a tidy distribution.

The uppercase stuff

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