spec/ruby/library/prime/integer/prime_spec.rb


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require_relative '../../../spec_helper'

ruby_version_is ""..."3.1" do
  require 'prime'

  describe "Integer#prime?" do
    it "returns a true value for prime numbers" do
      2.prime?.should be_true
      3.prime?.should be_true
      (2**31-1).prime?.should be_true  # 8th Mersenne prime (M8)
    end

    it "returns a false value for composite numbers" do
      4.prime?.should be_false
      15.prime?.should be_false
      (2**32-1).prime?.should be_false
      ( (2**17-1)*(2**19-1) ).prime?.should be_false  # M6*M7
    end
  end
end