Warn on RSpec comparisons between any time-like objects which may be sensitive to microsecond fluctuations in certain environments.

rspec_time_comparison_warning.rb

# This monkey patch modifies the RSpec `eq` matcher to suggest the `be_within`
# matcher instead when two time instances are being compared because equality
# comparison are inherently brittle on some operating systems like macOS so
# they may trigger false negatives.

module TimeComparisonWarning
  def failure_message
    msg = super

    if [expected, actual].any? { |obj| obj.respond_to?(:strftime) }
      msg << "\n"
      msg << <<~STRING
        WARNING: Comparing time instances with eq can be brittle.
        Try to use be_within(0.1).of(expected) to allow for microsecond fluctuations.
      STRING
    end
  end
end

class RSpec::Matchers::BuiltIn::Eq
  prepend TimeComparisonWarning
end

class RSpec::Matchers::BuiltIn::Eql
  prepend TimeComparisonWarning
end