1 files changed, 61 insertions, 0 deletions
diff --git a/spec/support/matchers/benchmark_matchers.rb b/spec/support/matchers/benchmark_matchers.rb
new file mode 100644
index 00000000000..84f655c2119
--- /dev/null
+++ b/spec/support/matchers/benchmark_matchers.rb
@@ -0,0 +1,61 @@
+module BenchmarkMatchers
+  extend RSpec::Matchers::DSL
+
+  def self.included(into)
+    into.extend(ClassMethods)
+  end
+
+  matcher :iterate_per_second do |min_iterations|
+    supports_block_expectations
+
+    match do |block|
+      @max_stddev ||= 30
+
+      @entry = benchmark(&block)
+
+      expect(@entry.ips).to be >= min_iterations
+      expect(@entry.stddev_percentage).to be <= @max_stddev
+    end
+
+    chain :with_maximum_stddev do |value|
+      @max_stddev = value
+    end
+
+    description do
+      "run at least #{min_iterations} iterations per second"
+    end
+
+    failure_message do
+      ips    = @entry.ips.round(2)
+      stddev = @entry.stddev_percentage.round(2)
+
+      "expected at least #{min_iterations} iterations per second " \
+        "with a maximum stddev of #{@max_stddev}%, instead of " \
+        "#{ips} iterations per second with a stddev of #{stddev}%"
+    end
+  end
+
+  # Benchmarks the given block and returns a Benchmark::IPS::Report::Entry.
+  def benchmark(&block)
+    report = Benchmark.ips(quiet: true) do |bench|
+      bench.report do
+        instance_eval(&block)
+      end
+    end
+
+    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