+ assert_equal (and must_equal) now tries to diff output where it mak…

…es sense.

+ Added Assertions.diff and diff=
+ Added Assertions#diff(exp, act) to be used by assert_equal.
+ Added Assertions#mu_pp_for_diff

[git-p4: depot-paths = "//src/minitest/dev/": change = 6259]

lib/minitest/unit.rb

@@ -59,16 +59,105 @@ def self.filter_backtrace bt # :nodoc:
 
   module Assertions
 
+    WINDOZE = RbConfig::CONFIG['host_os'] =~ /mswin|mingw/
+
+    ##
+    # Returns the diff command to use in #diff. Tries to intelligently
+    # figure out what diff to use.
+
+    def self.diff
+      @diff = if WINDOZE
+                "diff.exe -u"
+              else
+                if system("gdiff", __FILE__, __FILE__)
+                  "gdiff -u" # solaris and kin suck
+                elsif system("diff", __FILE__, __FILE__)
+                  "diff -u"
+                else
+                  nil
+                end
+              end unless defined? @diff
+
+      @diff
+    end
+
     ##
-    # mu_pp gives a human-readable version of +obj+.  By default #inspect is
-    # called.  You can override this to use #pretty_print if you want.
+    # Set the diff command to use in #diff.
+
+    def self.diff= o
+      @diff = o
+    end
+
+    ##
+    # Returns a diff between +exp+ and +act+. If there is no known
+    # diff command or if it doesn't make sense to diff the output
+    # (single line, short output), then it simply returns a basic
+    # comparison between the two.
+
+    def diff exp, act
+      require "tempfile"
+
+      expect = mu_pp_for_diff exp
+      butwas = mu_pp_for_diff act
+      result = nil
+
+      need_to_diff =
+        MiniTest::Assertions.diff &&
+        (expect.include?("\n")    ||
+         butwas.include?("\n")    ||
+         expect.size > 30         ||
+         butwas.size > 30         ||
+         expect == butwas)
+
+      return "Expected: #{mu_pp exp}\n  Actual: #{mu_pp act}" unless
+        need_to_diff
+
+      Tempfile.open("expect") do |a|
+        a.puts expect
+        a.rewind
+        Tempfile.open("butwas") do |b|
+          b.puts butwas
+          b.rewind
+
+          result = `#{MiniTest::Assertions.diff} #{a.path} #{b.path}`
+          result.sub!(/^\-\-\- .+/, "--- expected")
+          result.sub!(/^\+\+\+ .+/, "+++ actual")
+
+          if result.empty? then
+            klass = exp.class
+            result = [
+                      "No visible difference.",
+                      "You should look at your implementation of #{klass}#==.",
+                      expect
+                     ].join "\n"
+          end
+        end
+      end
+
+      result
+    end
+
+    ##
+    # This returns a human-readable version of +obj+. By default
+    # #inspect is called. You can override this to use #pretty_print
+    # if you want.
 
     def mu_pp obj
       s = obj.inspect
       s = s.force_encoding Encoding.default_external if defined? Encoding
       s
     end
 
+    ##
+    # This returns a diff-able human-readable version of +obj+. This
+    # differs from the regular mu_pp because it expands escaped
+    # newlines and makes hex-values generic (like object_ids). This
+    # uses mu_pp to do the first pass and then cleans it up.
+
+    def mu_pp_for_diff obj # TODO: possibly rename
+      mu_pp(obj).gsub(/\\n/, "\n").gsub(/0x[a-f0-9]+/m, '0xXXXXXX')
+    end
+
     def _assertions= n # :nodoc:
       @_assertions = n
     end
@@ -108,12 +197,19 @@ def assert_empty obj, msg = nil
     end
 
     ##
-    # Fails unless <tt>exp == act</tt>.
+    # Fails unless <tt>exp == act</tt> printing the difference between
+    # the two, if possible.
+    #
+    # If there is no visible difference but the assertion fails, you
+    # should suspect that your #== is buggy, or your inspect output is
+    # missing crucial details.
+    #
+    # For floats use assert_in_delta.
     #
-    # For floats use assert_in_delta
+    # See also: MiniTest::Assertions.diff
 
     def assert_equal exp, act, msg = nil
-      msg = message(msg) { "Expected #{mu_pp(exp)}, not #{mu_pp(act)}" }
+      msg = message(msg) { diff exp, act }
       assert(exp == act, msg)
     end
 

test/test_minitest_unit.rb

@@ -480,12 +480,113 @@ def test_assert_equal
     @tc.assert_equal 1, 1
   end
 
-  def test_assert_equal_different
-    util_assert_triggered "Expected 1, not 2." do
+  def test_assert_equal_different_diff_deactivated
+    without_diff do
+      util_assert_triggered util_msg("haha" * 10, "blah" * 10) do
+        o1 = "haha" * 10
+        o2 = "blah" * 10
+
+        @tc.assert_equal o1, o2
+      end
+    end
+  end
+
+  def test_assert_equal_different_hex
+    s = Struct.new :name
+
+    o1 = s.new "a"
+    o2 = s.new "b"
+    msg = "--- expected
+           +++ actual
+           @@ -1 +1 @@
+           -#{o1.inspect.sub(/0x\w+/, "0xXXXXXX")}
+           +#{o2.inspect.sub(/0x\w+/, "0xXXXXXX")}
+           .".gsub(/^ +/, "")
+
+    util_assert_triggered msg do
+      @tc.assert_equal o1, o2
+    end
+  end
+
+  def test_assert_equal_different_hex_invisible
+    o1 = Object.new
+    o2 = Object.new
+
+    msg = "No visible difference.
+           You should look at your implementation of Object#==.
+           #<Object:0xXXXXXX>.".gsub(/^ +/, "")
+
+    util_assert_triggered msg do
+      @tc.assert_equal o1, o2
+    end
+  end
+
+  def test_assert_equal_different_long
+    msg = "--- expected
+           +++ actual
+           @@ -1 +1 @@
+           -\"hahahahahahahahahahahahahahahahahahahaha\"
+           +\"blahblahblahblahblahblahblahblahblahblah\"
+           .".gsub(/^ +/, "")
+
+    util_assert_triggered msg do
+      o1 = "haha" * 10
+      o2 = "blah" * 10
+
+      @tc.assert_equal o1, o2
+    end
+  end
+
+  def test_assert_equal_different_long_invisible
+    msg = "No visible difference.
+           You should look at your implementation of String#==.
+           \"blahblahblahblahblahblahblahblahblahblah\".".gsub(/^ +/, "")
+
+    util_assert_triggered msg do
+      o1 = "blah" * 10
+      o2 = "blah" * 10
+      def o1.== o
+        false
+      end
+      @tc.assert_equal o1, o2
+    end
+  end
+
+  def test_assert_equal_different_long_msg
+    msg = "message.
+           --- expected
+           +++ actual
+           @@ -1 +1 @@
+           -\"hahahahahahahahahahahahahahahahahahahaha\"
+           +\"blahblahblahblahblahblahblahblahblahblah\"
+           .".gsub(/^ +/, "")
+
+    util_assert_triggered msg do
+      o1 = "haha" * 10
+      o2 = "blah" * 10
+      @tc.assert_equal o1, o2, "message"
+    end
+  end
+
+  def test_assert_equal_different_short
+    util_assert_triggered util_msg(1, 2) do
       @tc.assert_equal 1, 2
     end
   end
 
+  def test_assert_equal_different_short_msg
+    util_assert_triggered util_msg(1, 2, "message") do
+      @tc.assert_equal 1, 2, "message"
+    end
+  end
+
+  def test_assert_equal_different_short_multiline
+    msg = "--- expected\n+++ actual\n@@ -1,2 +1,2 @@\n \"a\n-b\"\n+c\"\n."
+    util_assert_triggered msg do
+      @tc.assert_equal "a\nb", "a\nc"
+    end
+  end
+
   def test_assert_in_delta
     @tc.assert_in_delta 0.0, 1.0 / 1000, 0.1
   end
@@ -636,7 +737,7 @@ def test_assert_output_out
   end
 
   def test_assert_output_triggered_both
-    util_assert_triggered "In stdout.\nExpected \"yay\", not \"boo\"." do
+    util_assert_triggered util_msg("yay", "boo", "In stdout") do
       @tc.assert_output "yay", "blah" do
         print "boo"
         $stderr.print "blah blah"
@@ -645,15 +746,15 @@ def test_assert_output_triggered_both
   end
 
   def test_assert_output_triggered_err
-    util_assert_triggered "In stderr.\nExpected \"blah\", not \"blah blah\"." do
+    util_assert_triggered util_msg("blah", "blah blah", "In stderr") do
       @tc.assert_output nil, "blah" do
         $stderr.print "blah blah"
       end
     end
   end
 
   def test_assert_output_triggered_out
-    util_assert_triggered "In stdout.\nExpected \"blah\", not \"blah blah\"." do
+    util_assert_triggered util_msg("blah", "blah blah", "In stdout") do
       @tc.assert_output "blah" do
         print "blah blah"
       end
@@ -832,15 +933,15 @@ def test_assert_silent
   def test_assert_silent_triggered_err
     @assertion_count = 2
 
-    util_assert_triggered "In stderr.\nExpected \"\", not \"blah blah\"." do
+    util_assert_triggered util_msg("", "blah blah", "In stderr") do
       @tc.assert_silent do
         $stderr.print "blah blah"
       end
     end
   end
 
   def test_assert_silent_triggered_out
-    util_assert_triggered "In stdout.\nExpected \"\", not \"blah blah\"." do
+    util_assert_triggered util_msg("", "blah blah", "In stdout") do
       @tc.assert_silent do
         print "blah blah"
       end
@@ -1148,4 +1249,19 @@ def util_assert_triggered expected, klass = MiniTest::Assertion
 
     assert_equal expected, msg
   end
+
+  def util_msg exp, act, msg = nil
+    s = "Expected: #{exp.inspect}\n  Actual: #{act.inspect}."
+    s = "#{msg}.\n#{s}" if msg
+    s
+  end
+
+  def without_diff
+    old_diff = MiniTest::Assertions.diff
+    MiniTest::Assertions.diff = nil
+
+    yield
+  ensure
+    MiniTest::Assertions.diff = old_diff
+  end
 end