Improve rake tasks for specs

- clean coverage directory before running specs to avoid simplecov
  slowdowns
- add valgrind task to run valgrind; normal spec does not run it
- delay combining and reporting simplecov results until end of task to
  speed up task execution

Rakefile.rb

@@ -1,3 +1,4 @@
+require "fileutils"
 require "rake/clean"
 require "rspec/core/rake_task"
 require "simplecov"
@@ -11,7 +12,10 @@ end
 
 RSpec::Core::RakeTask.new(:spec, :example_pattern) do |task, args|
   if args.example_pattern
+    ENV["partial_specs"] = "1"
     task.rspec_opts = %W[-e "#{args.example_pattern}" -f documentation]
+  else
+    FileUtils.rm_rf("coverage")
   end
 end
 task :spec do |task, args|
@@ -19,7 +23,7 @@ task :spec do |task, args|
     original_stdout = $stdout
     sio = StringIO.new
     $stdout = sio
-    SimpleCov.collate Dir["coverage/.resultset.json"]
+    SimpleCov.collate Dir["coverage/parts/*/.resultset.json"]
     $stdout = original_stdout
     sio.string.lines.each do |line|
       $stdout.write(line) unless line =~ /Coverage report generated for/
@@ -27,6 +31,15 @@ task :spec do |task, args|
   end
 end
 
+task :valgrind do
+  begin
+    ENV["spec-valgrind"] = "1"
+    Rake::Task[:spec].execute
+  ensure
+    ENV.delete("spec-valgrind")
+  end
+end
+
 # dspec task is useful to test the distributable release script, but is not
 # useful for coverage information.
 desc "Dist Specs"
@@ -43,4 +56,4 @@ task :user_guide do
   system("ruby", "-Ilib", "rb/gen_user_guide.rb")
 end
 
-task :all => [:spec, :dspec, :user_guide]
+task :all => [:valgrind, :dspec, :user_guide]

spec/propane_spec.rb

@@ -39,6 +39,11 @@ class MyFormatter
 end
 SimpleCov.start do
   command_name(#{command_name.inspect})
+  # Write this process's results to its own directory. Sharing one resultset
+  # file means every propane invocation must read, merge, and rewrite the
+  # results of all previous invocations, which grows quadratically over the
+  # suite. The parts are merged once at the end by the spec Rake task.
+  coverage_dir(#{"coverage/parts/#{command_name}".inspect})
   filters.clear
   add_filter do |src|
     !(src.filename[SimpleCov.root])
@@ -119,7 +124,7 @@ EOF
     results = Results.new(stdout, stderr, status)
     # Valgrind is only reliably available on Linux, so limit the leak check to
     # Linux platforms.
-    if RUBY_PLATFORM =~ /linux/
+    if RUBY_PLATFORM =~ /linux/ && ENV["spec-valgrind"]
       stdout, stderr, status = Open3.capture3("valgrind --leak-check=full --show-leak-kinds=all --track-origins=yes --verbose spec/run/testparser")
       vgout = stdout + stderr
       File.binwrite("spec/run/.vgout", vgout)

spec/spec_helper.rb

@@ -15,6 +15,10 @@ unless ENV["dist_specs"]
       command_name "RSpec"
     end
     project_name "Propane"
+    # Keep this process's results separate from the propane subprocess results
+    # so that nothing has to merge on the fly; the spec Rake task collates all
+    # of the parts once the suite is done.
+    coverage_dir "coverage/parts/rspec"
     merge_timeout 3600
     formatter(MyFormatter)
   end