One universal dry-run mock-spy AST evaluator to rule them all (iteration 3 of an effect EDSL)

Motivating example (from here):

public static string GetUpperText(string path) { if (!File.Exists(path)) return "DEFAULT"; var text = File.ReadAllText(path); return text.ToUpperInvariant(); } 

In PHP with the effect EDSL:

function getUpperText(string $file, St $st) { $result = 'DEFAULT'; $st ->if(fileExists($file)) ->then(set($result, fileGetContents($file))) (); return strtoupper($result); } 

In PHP with a mockable class:

function getUpperText(string $file, IO $io) { $result = 'DEFAULT'; if ($io->fileExists($file)) { $result = $io->fileGetContents($file); } return strtoupper($result); } 

The St class will build an abstract-syntax tree, which is then evaluated when invoked. It can be injected with either a live evaluator, or a dry-run evaluator which works as both mock, stub and spy.

St can also be used to delay or defer effects – just omit the invoke until later.

The unit test looks like this:

// Instead of mocking return types, set the return values $returnValues = [ true, 'Some example file content, bla bla bla' ]; $ev = new DryRunEvaluator($returnValues); $st = new St($ev); $text = getUpperText('moo.txt', $st); // Output: string(38) "SOME EXAMPLE FILE CONTENT, BLA BLA BLA" var_dump($text); // Instead of a spy, you can inspect the dry-run log var_dump($ev->log); /* Output: array(5) { [0] => string(13) "Evaluating if" [1] => string(27) "File exists: arg1 = moo.txt" [2] => string(15) "Evaluating then" [3] => string(33) "File get contents: arg1 = moo.txt" [4] => string(50) "Set var to: Some example file content, bla bla bla" } */ 

The St class scales differently than mocking, so it’s not always sensible to use.

Full code: https://gist.github.com/olleharstedt/e18004ad82e57e18047690596781a05a