I love my test suite

When I started to implement the evaluation of control-statements for the constant propagation I realized that I made a wrong decision. This occurred to me when I implemented the control-flow with a single if statement. One of the side-effects of such a statement is that it should undefine variables that are changed within the body when the condition can not be evaluated.
For example:

<?php
 $foo = 'bar';
 if($bar == 1){
   $foo = 'foo';
 }
//Value of $foo is unknown
?>

Because we do not know the value of $bar we do not know the value of $foo after the condition. So the dynamic rule that maps $foo to the string-value "bar" should be undefined. Stratego has special syntax for these kind of situations and this makes the implementation very easy.

When I wanted to do this for arrays I realized that arrays where implemented as a key-value mapping in a hashtable. This is correct, useful and it works, but undefining mappings takes a lot of work because the special notation would not work with this implementation. So I had to change this implementation and use dynamic rules.

My test suite really helped me in the refactoring of this implementation. It showed which part where updated correctly and I could use the tests to analyze why the rest still failed. It also made me aware of the fact the when a dynamic rule is undefined the key still exists. The application to this undefined key will always fail, as expected, but the key still remains in the set of all keys of a dynamic rule. The test suite also identified some hidden assumptions in the old implementation, which where immediately removed.

All this information would not have been available to me without the test suite. To quote a large company: "I'm loving it!"