Allow ordering specs by modification time

features/command_line/order.md

@@ -13,6 +13,10 @@ order of groups at each level is randomized.
 
 With `rand` you can also specify a seed.
 
+Use `recently-modified` to run the most recently modified files first. You can
+combine it with `--only-failures` to find the most recent failing specs. Note
+that `recently-modified` and `rand` are mutually exclusive.
+
 ## Example usage
 
 The `defined` option is only necessary when you have `--order rand` stored in a
@@ -22,4 +26,5 @@ config file (e.g. `.rspec`) and you want to override it from the command line.
 --order rand
 --order rand:123
 --seed 123 # same as --order rand:123
+--order recently-modified
 </code></pre>

lib/rspec/core/option_parser.rb

@@ -58,10 +58,11 @@ def parser(options)
         end
 
         parser.on('--order TYPE[:SEED]', 'Run examples by the specified order type.',
-                  '  [defined] examples and groups are run in the order they are defined',
-                  '  [rand]    randomize the order of groups and examples',
-                  '  [random]  alias for rand',
-                  '  [random:SEED] e.g. --order random:123') do |o|
+                  '  [defined]           examples and groups are run in the order they are defined',
+                  '  [rand]              randomize the order of groups and examples',
+                  '  [random]            alias for rand',
+                  '  [random:SEED]       e.g. --order random:123',
+                  '  [recently-modified] run the most recently modified files first') do |o|
           options[:order] = o
         end
 

lib/rspec/core/ordering.rb

@@ -58,6 +58,14 @@ def jenkins_hash_digest(string)
         MAX_32_BIT = 4_294_967_295
       end
 
+      # @private
+      # Orders items by modification time (most recent modified first).
+      class RecentlyModified
+        def order(list)
+          list.sort_by { |item| -File.mtime(item.metadata[:absolute_file_path]).to_i }
+        end
+      end
+
       # @private
       # Orders items based on a custom block.
       class Custom
@@ -77,7 +85,8 @@ def initialize(configuration)
           @configuration = configuration
           @strategies    = {}
 
-          register(:random,  Random.new(configuration))
+          register(:random, Random.new(configuration))
+          register(:recently_modified, RecentlyModified.new)
 
           identity = Identity.new
           register(:defined, identity)
@@ -132,6 +141,8 @@ def order=(type)
                             :random
                           elsif order == 'defined'
                             :defined
+                          elsif order == 'recently-modified'
+                            :recently_modified
                           end
 
           register_ordering(:global, ordering_registry.fetch(ordering_name)) if ordering_name

spec/integration/order_spec.rb

@@ -130,6 +130,17 @@
     end
   end
 
+  describe '--order rand --order recently-modified' do
+    it 'overrides random ordering with recently-modified option' do
+      2.times { run_command 'spec/order_spec.rb --order rand --order recently-modified -f doc' }
+
+      expect(stdout.string).not_to match(/Randomized with seed/)
+
+      top_level_groups { |first_run, second_run| expect(first_run).to eq(second_run) }
+      nested_groups { |first_run, second_run| expect(first_run).to eq(second_run) }
+    end
+  end
+
   describe '--order defined on CLI with --order rand in .rspec' do
     after { remove '.rspec' }
 

spec/rspec/core/ordering_spec.rb

@@ -81,6 +81,21 @@ def order_with(seed)
         end
       end
 
+      RSpec.describe RecentlyModified do
+        before do
+          allow(File).to receive(:mtime).with('./file_1.rb').and_return(::Time.new)
+          allow(File).to receive(:mtime).with('./file_2.rb').and_return(::Time.new + 1)
+        end
+
+        it 'orders list by file modification time' do
+          file_1 = instance_double(Example, :metadata => { :absolute_file_path => './file_1.rb' })
+          file_2 = instance_double(Example, :metadata => { :absolute_file_path => './file_2.rb' })
+          strategy = RecentlyModified.new
+
+          expect(strategy.order([file_1, file_2])).to eq([file_2, file_1])
+        end
+      end
+
       RSpec.describe Custom do
         it 'uses the block to order the list' do
           strategy = Custom.new(proc { |list| list.reverse })