Merge pull request #333 from rspec/make_match_diffable

expect().to match does not give a diff when failing

Changelog.md

@@ -9,6 +9,10 @@ Deprecations
   (for Ruby's conditional semantics) or `be true`/`be false`
   (for exact equality). (Sam Phippen)
 
+Bug fixes:
+
+* Make the `match` matcher produce a diff output (Jon Rowe, Ben Moss)
+
 ### 2.14.3 / 2013-09-22
 [full changelog](http://github.com/rspec/rspec-expectations/compare/v2.14.2...v2.14.3)
 

features/diffing.feature

@@ -43,7 +43,7 @@ Feature: diffing
         actual
           string
       ACTUAL
-          actual.should =~ expected
+          expect(actual).to match expected
         end
       end
       """

lib/rspec/matchers/built_in/match.rb

@@ -6,6 +6,11 @@ class Match < BaseMatcher
         def match(expected, actual)
           actual.match expected
         end
+
+        def diffable?
+          true
+        end
+
       end
     end
   end

spec/rspec/matchers/match_spec.rb

@@ -30,6 +30,19 @@
     matcher.matches?("string")
     expect(matcher.failure_message_for_should).to eq "expected \"string\" to match /rings/"
   end
+
+  it "provides a diff on failure" do
+    allow(RSpec::Matchers.configuration).to receive(:color?).and_return(false)
+
+    failure_message_that_includes_diff = %r%
+\s*Diff:
+\s*@@ -1,2 \+1,2 @@
+\s*-/bar/
+\s*\+"foo"%
+
+    expect { expect("foo").to match(/bar/) }.to fail_with(failure_message_that_includes_diff)
+  end
+
 end
 
 describe "expect(...).not_to match(expected)" do