Port assertion tests from pyvows to preggy

[Zearin]

Motivation

I recently published version 0.9.1. With bugs. Because all the stupid !#(*%ing tests passed!

(I discovered the bug when I ran the tests for heynemann/pyvows using the 0.9.1 release of preggy.)

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Preggy’s test coverage is good. That means the tests touch almost all of preggy’s code.

But preggy’s test quality is not-so-good. The tests may have visited almost all of preggy’s code, but it should have tested that code more rigorously. Otherwise, I wouldn’t have released 0.9.1 with the bug(s) in question. (Aside: bugs were related to to_be_an_error_with_message(), and the differences between str() and repr().)

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So I’m going to try my best to bring over some of pyvows’s assertion-related tests to preggy. Hopefully that will provide a more trustworthy test suite for future releases. :)