Add support for rspec mutant expression metadata

config/flay.yml

@@ -1,3 +1,3 @@
 ---
 threshold: 18
-total_score: 1240
+total_score: 1241

lib/mutant/integration/rspec.rb

@@ -111,19 +111,33 @@ module Mutant
       # @api private
       #
       def parse_example(example, index)
-        metadata = example.metadata
-        location = metadata.fetch(:location)
+        metadata         = example.metadata
+        location         = metadata.fetch(:location)
         full_description = metadata.fetch(:full_description)
 
-        match = EXPRESSION_CANDIDATE.match(full_description)
-        expression = Expression.try_parse(match.captures.first) || ALL
-
         Test.new(
           id:         "rspec:#{index}:#{location}/#{full_description}",
-          expression: expression
+          expression: parse_expression(metadata)
         )
       end
 
+      # Parse metadata into expression
+      #
+      # @param [RSpec::Core::Example::Medatada] metadata
+      #
+      # @return [Expression]
+      #
+      # @api private
+      #
+      def parse_expression(metadata)
+        if metadata.key?(:mutant_expression)
+          Expression.parse(metadata.fetch(:mutant_expression))
+        else
+          match = EXPRESSION_CANDIDATE.match(metadata.fetch(:full_description))
+          Expression.try_parse(match.captures.first) || ALL
+        end
+      end
+
       # Return all examples
       #
       # @return [Array<String, RSpec::Core::Example]

spec/unit/mutant/integration/rspec_spec.rb

@@ -47,12 +47,24 @@ RSpec.describe Mutant::Integration::Rspec do
     )
   end
 
+  let(:example_e) do
+    double(
+      'Example E',
+      metadata: {
+        location:          'example-e-location',
+        full_description:  'Example::E',
+        mutant_expression: 'Foo'
+      }
+    )
+  end
+
   let(:examples) do
     [
       example_a,
       example_b,
       example_c,
-      example_d
+      example_d,
+      example_e
     ]
   end
 
@@ -94,6 +106,10 @@ RSpec.describe Mutant::Integration::Rspec do
       Mutant::Test.new(
         id:         "rspec:2:example-d-location/Example::D\nblah",
         expression: Mutant::Expression.parse('*')
+      ),
+      Mutant::Test.new(
+        id:         'rspec:3:example-e-location/Example::E',
+        expression: Mutant::Expression.parse('Foo')
       )
     ]
   end