Caitiff

Caitiff is a toy library that implements assertions based on arbitrary ruby expressions and generates useful output. It was written as an experiment in what could be done and is not intended for actual use. If you’re interested in building it out for actual use, let me know!

Syntax

Write a file containing "laws" about how the system should behave. Caitiff includes a simple example file with the two laws listed below

in example_laws.rb

  law { 2 * 3 == 10 / 2 }
  law { 2 * 3 == 6 }

Judging

Laws are judged using the judge script, included in the Caitiff’s root directory. To run the example file you would type

  ruby -Ilib judge example_laws.rb

A rake task to do this is provided:

  rake example

Output

The judge produces the following output when judging the example

  Fallacy: ./example_laws.rb:1
    law { 2 * 3 == 10 / 2 }
    ----
    (6 == 5)

  2 laws, 1 truths, 1 fallacies

As you can see, it provides the original source code of the law followed by a simplified expression with the left and right hand sides evaluated. Instead of writing lots of custom assertions in your test code, you can use arbitrary ruby expressions and still get more useful output than "expected true, but was false."