fix: closeTo should check value's type before assertion

[mohayonao]

Assertion#closeTo passes tests that should be failed.

e.g.

expect([1.5]).to.be.closeTo(1.0, 0.5); // PASS???
expect(1.5).to.be.closeTo("1.0", 0.5); // PASS???

so, I fixed it.

expect([1.5]).to.be.closeTo(1.0, 0.5); // throw "expected [ 1.5 ] to be a number"
expect(1.5).to.be.closeTo("1.0", 0.5); // throw "expected '1.0' to be a number"

[charlierudolph]

👍 Definitely a useful error message.

I think the message should be different though when the supplied arguments to closeTo are wrong versus the actual value. Should probably verify delta is a number too.

expect([1.5]).to.be.closeTo(1.0, 0.5); // throw "expected [ 1.5 ] to be a number"
expect(1.5).to.be.closeTo("1.0", 0.5); // throw "the arguments to closeTo must be numbers"
expect(1.5).to.be.closeTo(1.0, "0.5"); // throw "the arguments to closeTo must be numbers"

[mohayonao]

I agree.
I've fixed this commit to throw understandable error messages.
Thanks!

expect([1.5]).to.be.closeTo(1.0, 0.5); // throw "expected [ 1.5 ] to be a number"
expect(1.5).to.be.closeTo("1.0", 0.5); // throw "the arguments to closeTo must be numbers"
expect(1.5).to.be.closeTo(1.0, "0.5"); // throw "the arguments to closeTo must be numbers"