Added benchmark_subject method for benchmarks

This class method can be used in "describe" blocks to specify the
subject of a benchmark. This lets you write:

    benchmark_subject { Foo }

instead of:

    benchmark_subject { -> { Foo } }

1 files changed, 17 insertions, 0 deletions

diff --git a/spec/support/matchers/benchmark_matchers.rb b/spec/support/matchers/benchmark_matchers.rb
index 45a1d49345f..b73a53917f0 100644
--- a/spec/support/matchers/benchmark_matchers.rb
+++ b/spec/support/matchers/benchmark_matchers.rb
@@ -1,6 +1,10 @@
 module BenchmarkMatchers
   extend RSpec::Matchers::DSL
 
+  def self.included(into)
+    into.extend(ClassMethods)
+  end
+
   matcher :iterate_per_second do |min_iterations|
     supports_block_expectations
 
@@ -39,4 +43,17 @@ module BenchmarkMatchers
 
     report.entries[0]
   end
+
+  module ClassMethods
+    # Wraps around rspec's subject method so you can write:
+    #
+    #     benchmark_subject { SomeClass.some_method }
+    #
+    # instead of:
+    #
+    #     subject { -> { SomeClass.some_method } }
+    def benchmark_subject(&block)
+      subject { block }
+    end
+  end
 end