Add tests for Time.at with BigDecimal input

[alex88]

I've added a test that checks if Time.at rounds the input when a float BigDecimal is passed.

Probably the place of the test is wrong so let me know where it should be moved and I'll be happy to do that.

This relates to jruby/jruby#3616

[eregon]

Time.at is part of the core library, so it should be in https://github.com/ruby/spec/blob/master/core/time/at_spec.rb.
But indeed this spec example requires the bigdecimal stdlib.

Therefore I would say move it to core and move the require 'bigdecimal' in the example so only that one would fail if bigdecimal was not available.
(An alternative would be to do this with mocks to check that to_r is tried before to_int but it seems tricky and would still leave plenty of room for implementations to fail with a real BigDecimal, so I like this more realistic test.)

[alex88]

Let me know if that works for you, however, wouldn't it be better to actually check if require fails and in that case mark the test as skipped? Since in that case it's not a real failure (even if stdlib should be always available)

[eregon]

The require should be in the it block.

[eregon]

Let me know if that works for you, however, wouldn't it be better to actually check if require fails and in that case mark the test as skipped? Since in that case it's not a real failure (even if stdlib should be always available)

There is a system of tags allowing to skip one example easily so it's not a problem in practice AFAIK.

[alex88]

Done, let me know if you wanted also the describe inside the Numeric examples or just the it with something like doesn't round BigDecimal

[eregon]

It's good as-is, merged, thank you for your contribution! 😃