assert: throw when block is not a function

[cjihrig]

Currently, anything passed as the block argument to throws() and doesNotThrow() is interpreted as a function, which can lead to unexpected results. This commit checks the type of block, and throws a TypeError if it is not a function.

We might want to hold off until after 1.0.0, not sure. Closes #275.

R=@bnoordhuis

[bnoordhuis]

LGTM

[cjihrig]

@bnoordhuis should I land this before or after 1.0.0? It's a small behavior change. Also, how do you feel about this somewhat related PR - nodejs/node-v0.x-archive#8734

[bnoordhuis]

I think this PR can land now, the current behavior is never the desired one. Worst case, it exposes bugs in people's test suites.

nodejs/node-v0.x-archive#8734 looks reasonable at a glance but perhaps needs more careful inspection. I could see it cause regressions when you .deepEqual() on very large objects, for example.

[cjihrig]

I could see it cause regressions when you .deepEqual() on very large objects, for example.

Could you elaborate? Does util.inspect() not work with large objects? I assumed the only regressions would occur if you were comparing the AssertionError messages.

[bnoordhuis]

It works but it can be very slow. I suppose it's only an issue when the assert fails.

[cjihrig]

Landed in 14dc917