Ensure that negative versions of matchers are tested

Author: mcmire

lib/super_diff/rspec/differ.rb

@@ -44,7 +44,7 @@ def worth_diffing?
       end
 
       def comparing_inequal_values?
-        expected != actual
+        !helpers.values_match?(expected, actual)
       end
 
       def comparing_primitive_values?
@@ -59,6 +59,16 @@ def comparing_singleline_strings?
           !expected.include?("\n") &&
           !actual.include?("\n")
       end
+
+      def helpers
+        @_helpers ||= Helpers.new
+      end
+
+      class Helpers
+        include ::RSpec::Matchers::Composable
+
+        public :values_match?
+      end
     end
   end
 end

lib/super_diff/rspec/matcher_text_builders/be_predicate.rb

@@ -18,7 +18,7 @@ def initialize(
 
         def expected_action_for_failure_message
           if predicate_accessible?
-            "return true for"
+            "return a truthy result for"
           elsif private_predicate?
             "have a public method"
           else

lib/super_diff/rspec/monkey_patches.rb

@@ -380,6 +380,8 @@ def expected_for_description
 
           # Override to use readable_list_of
           def expected_for_failure_message
+            # TODO: Switch to using @divergent_items and handle this in the text
+            # builder
             readable_list_of(@divergent_items).lstrip
           end
 

spec/integration/rspec/be_falsey_matcher_spec.rb

@@ -1,7 +1,7 @@
 require "spec_helper"
 
 RSpec.describe "Integration with RSpec's #be_falsey matcher", type: :integration do
-  it "produces the correct failure message" do
+  it "produces the correct failure message when used in the positive" do
     as_both_colored_and_uncolored do |color_enabled|
       snippet = %|expect(:foo).to be_falsey|
       program = make_plain_test_program(snippet, color_enabled: color_enabled)
@@ -25,4 +25,29 @@
         in_color(color_enabled)
     end
   end
+
+  it "produces the correct failure message when used in the negative" do
+    as_both_colored_and_uncolored do |color_enabled|
+      snippet = %|expect(false).not_to be_falsey|
+      program = make_plain_test_program(snippet, color_enabled: color_enabled)
+
+      expected_output = build_expected_output(
+        color_enabled: color_enabled,
+        snippet: snippet,
+        expectation: proc {
+          line do
+            plain "Expected "
+            green %|false|
+            plain " not to be "
+            red %|falsey|
+            plain "."
+          end
+        },
+      )
+
+      expect(program).
+        to produce_output_when_run(expected_output).
+        in_color(color_enabled)
+    end
+  end
 end