Use more display precision for Time and DateTime

lib/rspec/matchers/built_in/eq.rb

@@ -7,18 +7,47 @@ def match(expected, actual)
         end
 
         def failure_message
-          "\nexpected: #{expected.inspect}\n     got: #{actual.inspect}\n\n(compared using ==)\n"
+          "\nexpected: #{format_object(expected)}\n     got: #{format_object(actual)}\n\n(compared using ==)\n"
         end
 
         def failure_message_when_negated
-          "\nexpected: value != #{expected.inspect}\n     got: #{actual.inspect}\n\n(compared using ==)\n"
+          "\nexpected: value != #{format_object(expected)}\n     got: #{format_object(actual)}\n\n(compared using ==)\n"
         end
 
         def description
           "#{name_to_sentence} #{@expected.inspect}"
         end
 
         def diffable?; true; end
+
+      private
+
+        def format_object(object)
+          if Time === object
+            format_time(object)
+          elsif defined?(DateTime) && DateTime === object
+            format_date_time(object)
+          else
+            object.inspect
+          end
+        end
+
+        TIME_FORMAT = "%Y-%m-%d %H:%M:%S"
+        # Append microseconds to the default format string
+        def format_time(time)
+          time.strftime("#{TIME_FORMAT}.#{"%06d" % time.usec} %z")
+        end
+
+        DATE_TIME_FORMAT = "%a, %d %b %Y %H:%M:%S.%6N %z"
+        # ActiveSupport sometimes overrides inspect. If `ActiveSupport` is
+        # defined use a custom format string that includes more time precision.
+        def format_date_time(date_time)
+          if defined?(ActiveSupport)
+            date_time.strftime(DATE_TIME_FORMAT)
+          else
+            date_time.inspect
+          end
+        end
       end
     end
   end

spec/rspec/matchers/built_in/eq_spec.rb

@@ -90,7 +90,70 @@ module Matchers
           end
         end
       end
+
+      context "Time Equality" do
+        RSpec::Matchers.define :a_string_with_differing_output do
+          match do |string|
+            time_strings = /expected: (.+)\n.*got: (.+)$/.match(string).captures
+            time_strings.uniq.count == 2
+          end
+        end
+
+        RSpec::Matchers.define :a_string_with_identical_output do
+          match do |string|
+            time_strings = /expected: value != (.+)\n.*got: (.+)$/.match(string).captures
+            time_strings.uniq.count == 1
+          end
+        end
+
+        context 'with Time objects' do
+          let(:time1) { Time.utc(1969, 12, 31, 19, 01, 40, 101) }
+          let(:time2) { Time.utc(1969, 12, 31, 19, 01, 40, 102) }
+
+          it 'Should have a different output string when differing by milliseconds' do
+            expect {
+              expect(time1).to eq(time2)
+            }.to fail_with(a_string_with_differing_output)
+          end
+        end
+
+        context 'with DateTime objects' do
+          require 'date'
+          let(:date1) { DateTime.new(2000, 1, 1, 1, 1, Rational(1, 10)) }
+          let(:date2) { DateTime.new(2000, 1, 1, 1, 1, Rational(2, 10)) }
+
+          it 'Should have diffferent output string when differing by milliseconds' do
+            expect {
+              expect(date1).to eq(date2)
+            }.to fail_with(a_string_with_differing_output)
+          end
+
+          it 'should not raise an exception if DateTime is not defined' do
+            hide_const('DateTime')
+            expect {
+              expect(5).to eq(4)
+            }.to raise_error(RSpec::Expectations::ExpectationNotMetError)
+          end
+
+          it 'fails with identical messages' do
+            expect {
+              expect(date1).to_not eq(date1)
+            }.to fail_with(a_string_with_identical_output)
+          end
+
+          describe 'ActiveSuppot is defined' do
+            it 'fails with a differing message' do
+              stub_const("ActiveSupport", Module.new)
+              allow(date1).to receive(:inspect).and_return("Timestamp")
+              allow(date2).to receive(:inspect).and_return("Timestamp")
+
+              expect {
+                expect(date1).to eq(date2)
+              }.to fail_with(a_string_with_differing_output)
+            end
+          end
+        end
+      end
     end
   end
 end
-