1 files changed, 66 insertions, 0 deletions
diff --git a/spec/ruby/library/bigdecimal/minus_spec.rb b/spec/ruby/library/bigdecimal/minus_spec.rb
new file mode 100644
index 0000000000..bd3c19584b
--- /dev/null
+++ b/spec/ruby/library/bigdecimal/minus_spec.rb
@@ -0,0 +1,66 @@
+require_relative '../../spec_helper'
+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