1 files changed, 49 insertions, 0 deletions
diff --git a/spec/ruby/core/float/next_float_spec.rb b/spec/ruby/core/float/next_float_spec.rb
new file mode 100644
index 0000000000..d5a7748a06
--- /dev/null
+++ b/spec/ruby/core/float/next_float_spec.rb
@@ -0,0 +1,49 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+
+describe "Float#next_float" do
+  it "returns a float the smallest possible step greater than the receiver" do
+    barely_positive = 0.0.next_float
+    barely_positive.should == 0.0.next_float
+
+    barely_positive.should > 0.0
+    barely_positive.should < barely_positive.next_float
+
+    midpoint = barely_positive / 2
+    [0.0, barely_positive].should include midpoint
+  end
+
+  it "returns Float::INFINITY for Float::INFINITY" do
+    Float::INFINITY.next_float.should == Float::INFINITY
+  end
+
+  it "steps directly between MAX and INFINITY" do
+    (-Float::INFINITY).next_float.should == -Float::MAX
+    Float::MAX.next_float.should == Float::INFINITY
+  end
+
+  it "steps directly between 1.0 and 1.0 + EPSILON" do
+    1.0.next_float.should == 1.0 + Float::EPSILON
+  end
+
+  it "steps directly between -1.0 and -1.0 + EPSILON/2" do
+    (-1.0).next_float.should == -1.0 + Float::EPSILON/2
+  end
+
+  it "reverses the effect of prev_float for all Floats except INFINITY and +0.0" do
+    num = -rand
+    num.prev_float.next_float.should == num
+  end
+
+  it "returns negative zero when stepping upward from just below zero" do
+    x = (-0.0).prev_float.next_float
+    (1/x).should == -Float::INFINITY
+  end
+
+  it "gives the same result for -0.0 as for +0.0" do
+    (-0.0).next_float.should == (0.0).next_float
+  end
+
+  it "returns NAN if NAN was the receiver" do
+    Float::NAN.next_float.nan?.should == true
+  end
+end