Fix RSpec warnings for "potential false positives"

[danielsdeleo]

RSpec now emits these warnings:

WARNING: Using the `raise_error` matcher without providing a specific error or message risks false positives, since `raise_error` will match when Ruby raises a `NoMethodError`, `NameError` or `ArgumentError`, potentially allowing the expectation to pass without even executing the method you are intending to call. Instead consider providing a specific error class or message. This message can be supressed by setting: `RSpec::Expectations.configuration.warn_about_potential_false_positives = false`.

Fixed in this commit.

[jaym]

👍

[tyler-ball]