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path: root/spec/ruby/library/bigdecimal/minus_spec.rb
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require_relative '../../spec_helper'

ruby_version_is ""..."3.4" do
  require 'bigdecimal'

  describe "BigDecimal#-" do

    before :each do
      @one = BigDecimal("1")
      @zero = BigDecimal("0")
      @two = BigDecimal("2")
      @nan = BigDecimal("NaN")
      @infinity = BigDecimal("Infinity")
      @infinity_minus = BigDecimal("-Infinity")
      @one_minus = BigDecimal("-1")
      @frac_1 = BigDecimal("1E-99999")
      @frac_2 = BigDecimal("0.9E-99999")
    end

    it "returns a - b" do
      (@two - @one).should == @one
      (@one - @two).should == @one_minus
      (@one - @one_minus).should == @two
      (@frac_2 - @frac_1).should == BigDecimal("-0.1E-99999")
      (@two - @two).should == @zero
      (@frac_1 - @frac_1).should == @zero
      (BigDecimal('1.23456789') - BigDecimal('1.2')).should == BigDecimal("0.03456789")
    end

    it "returns NaN if NaN is involved" do
      (@one - @nan).should.nan?
      (@nan - @one).should.nan?
      (@nan - @nan).should.nan?
      (@nan - @infinity).should.nan?
      (@nan - @infinity_minus).should.nan?
      (@infinity - @nan).should.nan?
      (@infinity_minus - @nan).should.nan?
    end

    it "returns NaN both operands are infinite with the same sign" do
      (@infinity - @infinity).should.nan?
      (@infinity_minus - @infinity_minus).should.nan?
    end

    it "returns Infinity or -Infinity if these are involved" do
      (@infinity - @infinity_minus).should == @infinity
      (@infinity_minus - @infinity).should == @infinity_minus

      (@infinity - @zero).should == @infinity
      (@infinity - @frac_2).should == @infinity
      (@infinity - @two).should == @infinity
      (@infinity - @one_minus).should == @infinity

      (@zero - @infinity).should == @infinity_minus
      (@frac_2 - @infinity).should == @infinity_minus
      (@two - @infinity).should == @infinity_minus
      (@one_minus - @infinity).should == @infinity_minus
    end

    describe "with Object" do
      it "tries to coerce the other operand to self" do
        object = mock("Object")
        object.should_receive(:coerce).with(@one).and_return([@one, BigDecimal("42")])
        (@one - object).should == BigDecimal("-41")
      end
    end

  end
end