Thursday, November 19, 2009

Phexample's lolcats syntax

In this post I'll clear my throat on what there is to come. The number one criticism of Phexample is that Phexample sometimes reads like lolcats, because real code that asserts that a stack be empty reads like

stack should not be isEmpty.

The complaint feels like an instance of the complaint of how stupid it is that in OSX you need to drag CDs to the waste bin to eject them, or how in Windows the bin stands on the desk. Of course the metaphor is broken there, but you only notice it because the metaphor works great.

And now you compare that to the usual alternative, which is assert. The first thing you know about assert is that nobody can remember which one is the expected and which is the actual value (I'll take this fact and some of the below discussion from Josh Graham's discussion of the assert syntax). We're talking about assertEquals(stack.isEmpty, true). Or the other way around. I certainly can't remember that either.

In Java, improvements have been suggested:
assertEquals(expected(true), actual(stack.isEmpty());

I find that while Phexample does not allow you to express your examples in a way that completely parses as natural language, it certainly reads easy enough and gives a natural and easy distinction between the expected and the actual.

So there's my analogy: no other testing framework is required to express its tests in a way that perfectly parses as human language. Only because the tests already look so close to perfection is it that people single out the mismatch and decry it. I don't think this is an interesting problem worth solving at all.

Yet, the criticism follows Phexample wherever it goes, so I'll try and allow phrases like

stack isEmpty should be true.

The difficulty in making the above code work is that the testing framework is only activated after isEmpty was evaluated already. Which means that it isn't in the stack anymore, so we need to analyze the source code to find out which method caused the failure to display a meaningful error message.

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