Change the be_within matcher to be inclusive of the delta.

- Fixes rspec#131.
- This changes the way the matcher behaves, which is something we would
  generally avoid in anything but a major release, however we believe
  that this is the correct behavior and that this change is very unlikely
  to impact anybody negatively. Specifically:

  1. 17.4.should be_within(0.5).of(17) # used to pass and continues to pass
  2. 17.5.should be_within(0.5).of(17) # used to fail due to lack of inclusivity, but passes after this change
  3. 17.6.should be_within(0.5).of(17) # used to fail and continues to fail
  4. 17.4.should_not be_within(0.5).of(17) # used to fail and continues to fail
  5. 17.5.should_not be_within(0.5).of(17) # used to pass due to lack of inclusivity, but fails after this change
  6. 17.6.should_not be_within(0.5).of(17) # used to fail and continues to fail

  Scenario 2 used to fail, so it's unlikely to be present.
  Scenario 5 will result in new failures, but we believe that it is very unlikely to be used.

Changelog.md

@@ -8,6 +8,7 @@ Bug fixes
 * Fix for error with using custom matchers inside other custom matchers
   (mirasrael)
 * Fix using execution context methods in nested DSL matchers (mirasrael)
+* Fix `be_within` matcher to be inclusive of delta.
 
 ### 2.9.0 / 2012-03-17
 [full changelog](http://github.com/rspec/rspec-expectations/compare/v2.8.0...v2.9.0)

features/built_in_matchers/be_within.feature

@@ -23,21 +23,24 @@ Feature: be_within matcher
       """
       describe 27.5 do
         it { should be_within(0.5).of(27.9) }
+        it { should be_within(0.5).of(28.0) }
         it { should be_within(0.5).of(27.1) }
-        it { should_not be_within(0.5).of(28) }
-        it { should_not be_within(0.5).of(27) }
+        it { should be_within(0.5).of(27.0) }
+
+        it { should_not be_within(0.5).of(28.1) }
+        it { should_not be_within(0.5).of(26.9) }
 
         # deliberate failures
-        it { should_not be_within(0.5).of(27.9) }
-        it { should_not be_within(0.5).of(27.1) }
-        it { should be_within(0.5).of(28) }
-        it { should be_within(0.5).of(27) }
+        it { should_not be_within(0.5).of(28) }
+        it { should_not be_within(0.5).of(27) }
+        it { should be_within(0.5).of(28.1) }
+        it { should be_within(0.5).of(26.9) }
       end
       """
     When I run `rspec be_within_matcher_spec.rb`
     Then the output should contain all of these:
-      | 8 examples, 4 failures                     |
-      | expected 27.5 not to be within 0.5 of 27.9 |
-      | expected 27.5 not to be within 0.5 of 27.1 |
-      | expected 27.5 to be within 0.5 of 28       |
-      | expected 27.5 to be within 0.5 of 27       |
+      | 10 examples, 4 failures                     |
+      | expected 27.5 not to be within 0.5 of 28   |
+      | expected 27.5 not to be within 0.5 of 27   |
+      | expected 27.5 to be within 0.5 of 28.1     |
+      | expected 27.5 to be within 0.5 of 26.9     |

lib/rspec/matchers/built_in/be_within.rb

@@ -14,7 +14,7 @@ def matches?(actual)
           unless defined?(@expected)
             raise ArgumentError.new("You must set an expected value using #of: be_within(#{delta}).of(expected_value)")
           end
-          (super(actual) - expected).abs < delta
+          (super(actual) - expected).abs <= delta
         end
 
         def of(expected)

spec/rspec/matchers/be_within_spec.rb

@@ -15,16 +15,16 @@ module Matchers
         be_within(0.5).of(5.0).matches?(4.51).should be_true
       end
 
-      it "does not match when actual == (expected - delta)" do
-        be_within(0.5).of(5.0).matches?(4.5).should be_false
+      it "matches when actual == (expected - delta)" do
+        be_within(0.5).of(5.0).matches?(4.5).should be_true
       end
 
       it "does not match when actual < (expected - delta)" do
         be_within(0.5).of(5.0).matches?(4.49).should be_false
       end
 
-      it "does not match when actual == (expected + delta)" do
-        be_within(0.5).of(5.0).matches?(5.5).should be_false
+      it "matches when actual == (expected + delta)" do
+        be_within(0.5).of(5.0).matches?(5.5).should be_true
       end
 
       it "does not match when actual > (expected + delta)" do