string_boolean.rb

class StringBoolean
  class << self
    TRUE  = "1".freeze
    FALSE = "0".freeze

    TRUTHY = ["1", "t", "y", "true", "yes"].freeze
    FALSEY = ["0", "f", "n", "false", "no", ""].freeze

    def true
      TRUE
    end

    def false
      FALSE
    end

    def truthy?(value)
      TRUTHY.include?(value.to_s.downcase)
    end

    def falsey?(value)
      FALSEY.include?(value.to_s.downcase)
    end
  end
end

Added another method truthy_or_falsey? to check that the value is either true or false so will return false if you send an invalid string

def truthy_or_falsey?(value)
  FALSEY.include?(value.to_s.downcase) || TRUTHY.include?(value.to_s.downcase)
end

# False
# StringBoolean.truthy_or_falsey?("Bob")