JS tests for PDFBlock

[kdmccormick]

The PDFBlock has no JS tests currently. The JS is very minimal, so all we would need are 1-3 test cases that there isn't like a critical syntax error in the JS.

Blocked by #63, which will add the initial set of (ProblemBlock) JS tests to the repo.

[kdmccormick]

@Kelketek do you mind commenting here so that GH will let me assign you?

[Kelketek]

@kdmccormick Done.