Add specs for edge cases.

Author: aardvark179

spec/ruby/core/float/round_spec.rb

@@ -109,7 +109,38 @@
     -5.55.round(1, half: :even).should eql(-5.6)
   end
 
+  it "preserves cases where neighbouring floating pointer number increase the decimal places" do
+    4.8100000000000005.round(5, half: nil).should eql(4.81)
+    4.8100000000000005.round(5, half: :up).should eql(4.81)
+    4.8100000000000005.round(5, half: :down).should eql(4.81)
+    4.8100000000000005.round(5, half: :even).should eql(4.81)
+    -4.8100000000000005.round(5, half: nil).should eql(-4.81)
+    -4.8100000000000005.round(5, half: :up).should eql(-4.81)
+    -4.8100000000000005.round(5, half: :down).should eql(-4.81)
+    -4.8100000000000005.round(5, half: :even).should eql(-4.81)
+    4.81.round(5, half: nil).should eql(4.81)
+    4.81.round(5, half: :up).should eql(4.81)
+    4.81.round(5, half: :down).should eql(4.81)
+    4.81.round(5, half: :even).should eql(4.81)
+    -4.81.round(5, half: nil).should eql(-4.81)
+    -4.81.round(5, half: :up).should eql(-4.81)
+    -4.81.round(5, half: :down).should eql(-4.81)
+    -4.81.round(5, half: :even).should eql(-4.81)
+    4.809999999999999.round(5, half: nil).should eql(4.81)
+    4.809999999999999.round(5, half: :up).should eql(4.81)
+    4.809999999999999.round(5, half: :down).should eql(4.81)
+    4.809999999999999.round(5, half: :even).should eql(4.81)
+    -4.809999999999999.round(5, half: nil).should eql(-4.81)
+    -4.809999999999999.round(5, half: :up).should eql(-4.81)
+    -4.809999999999999.round(5, half: :down).should eql(-4.81)
+    -4.809999999999999.round(5, half: :even).should eql(-4.81)
+  end
+
   ruby_bug "", ""..."3.2" do
+    # These numbers are neighbouring floating point numbers round a
+    # precise value. They test that the rounding modes work correctly
+    # round that value and precision is not lost which might cause
+    # incorrect results.
     it "does not lose precision during the rounding process" do
       767573.1875850001.round(5, half: nil).should eql(767573.18759)
       767573.1875850001.round(5, half: :up).should eql(767573.18759)
@@ -119,6 +150,14 @@
       -767573.1875850001.round(5, half: :up).should eql(-767573.18759)
       -767573.1875850001.round(5, half: :down).should eql(-767573.18759)
       -767573.1875850001.round(5, half: :even).should eql(-767573.18759)
+      767573.187585.round(5, half: nil).should eql(767573.18759)
+      767573.187585.round(5, half: :up).should eql(767573.18759)
+      767573.187585.round(5, half: :down).should eql(767573.18758)
+      767573.187585.round(5, half: :even).should eql(767573.18758)
+      -767573.187585.round(5, half: nil).should eql(-767573.18759)
+      -767573.187585.round(5, half: :up).should eql(-767573.18759)
+      -767573.187585.round(5, half: :down).should eql(-767573.18758)
+      -767573.187585.round(5, half: :even).should eql(-767573.18758)
       767573.1875849998.round(5, half: nil).should eql(767573.18758)
       767573.1875849998.round(5, half: :up).should eql(767573.18758)
       767573.1875849998.round(5, half: :down).should eql(767573.18758)