Improve raise_error messages (#218)

This commit makes some minor changes to the `raise_error` matcher to
make the failure messages slightly more friendly and consistent with the
overall philosophy of matchers in this repo.

Here are the current messages in comparison with the new ones:

- In cases where the block raises no error, the wording changes from
"Expected block" to "Expected exception-free block", and "exception-free
block" is highlighted in the actual color. This is to emphasize the
actual behavior vs. the expected behavior and matches other matchers.
- In cases where only an expected error class is provided, the wording
changes so that instead of inspecting the expected error, the failure
message says "a kind of" followed by the class name.
- In cases where a message is provided, the expected class and message
are separated in the failure message.
- In cases where a regexp message is provided, the wording changes from
"with message #{message}" to "with message matching #{message}".

Additionally, the integration tests for `raise_error` have been reviewed
and missing tests have been filled in.

lib/super_diff/rspec/matcher_text_builders/raise_error.rb

@@ -5,14 +5,10 @@ class RaiseError < Base
         protected
 
         def actual_phrase
-          actual ? "Expected raised exception" : "Expected"
-        end
-
-        def add_actual_value
-          if actual
-            template.add_text_in_color(actual_color) { actual }
+          if actual == "exception-free block"
+            "Expected"
           else
-            template.add_text("block")
+            "Expected raised exception"
           end
         end
       end

lib/super_diff/rspec/monkey_patches.rb

@@ -722,9 +722,15 @@ class RaiseError
         SuperDiff.insert_overrides(self, SuperDiff::RSpec::AugmentedMatcher)
 
         SuperDiff.insert_overrides(self) do
+          def expected_action_for_description
+            "raise"
+          end
+
           def actual_for_matcher_text
             if @actual_error
               "#<#{@actual_error.class.name} #{@actual_error.message.inspect}>"
+            else
+              "exception-free block"
             end
           end
 
@@ -733,10 +739,19 @@ def actual_for_diff
           end
 
           def expected_for_matcher_text
-            if @expected_message
-              "#<#{describe_expected_error} #{description_of(@expected_message)}>"
+            case @expected_message
+            when nil
+              if RSpec::Matchers.is_a_describable_matcher?(@expected_error)
+                description_of(@expected_error)
+              elsif @expected_error.is_a?(Regexp)
+                "a kind of Exception with message matching #{description_of(@expected_error)}"
+              else
+                "a kind of #{@expected_error}"
+              end
+            when Regexp
+              "#{described_expected_error} with message matching #{description_of(@expected_message)}"
             else
-              "#<#{describe_expected_error}>"
+              "#{described_expected_error} with message #{description_of(@expected_message)}"
             end
           end
 
@@ -749,7 +764,7 @@ def diffable?
           end
 
           def expected_action_for_failure_message
-            @actual_error ? "match" : "raise error"
+            @actual_error ? "match" : "raise"
           end
 
           def matcher_text_builder_class
@@ -758,15 +773,11 @@ def matcher_text_builder_class
 
           private
 
-          def describe_expected_error
-            if @expected_error.is_a? Class
-              @expected_error.name
-            elsif @expected_error.is_a? Regexp
-              "Exception #{description_of(@expected_error)}"
-            elsif @expected_error.respond_to? :description
-              @expected_error.description
+          def described_expected_error
+            if @expected_error.is_a?(Class)
+              "a kind of #{@expected_error}"
             else
-              SuperDiff.inspect_object(@expected_error, as_lines: false)
+              description_of(@expected_error)
             end
           end
         end