diff --git a/lib/rake/application.rb b/lib/rake/application.rb
index ae594e098..8c896888f 100644
--- a/lib/rake/application.rb
+++ b/lib/rake/application.rb
@@ -62,6 +62,8 @@ def initialize
       add_loader("rake", DefaultLoader.new)
       @tty_output = STDOUT.tty?
       @terminal_columns = ENV["RAKE_COLUMNS"].to_i
+
+      set_default_options
     end
 
     # Run the Rake application.  The run method performs the following
@@ -74,19 +76,19 @@ def initialize
     # If you wish to build a custom rake command, you should call
     # +init+ on your application.  Then define any tasks.  Finally,
     # call +top_level+ to run your top level tasks.
-    def run
+    def run(argv = ARGV)
       standard_exception_handling do
-        init
+        init 'rake', argv
         load_rakefile
         top_level
       end
     end
 
     # Initialize the command line parameters and app name.
-    def init(app_name="rake")
+    def init(app_name="rake", argv = ARGV)
       standard_exception_handling do
         @name = app_name
-        args = handle_options
+        args = handle_options argv
         collect_command_line_tasks(args)
       end
     end
@@ -618,9 +620,8 @@ def select_trace_output(options, trace_option, value) # :nodoc:
     # Read and handle the command line options.  Returns the command line
     # arguments that we didn't understand, which should (in theory) be just
     # task names and env vars.
-    def handle_options # :nodoc:
-      options.rakelib = ["rakelib"]
-      options.trace_output = $stderr
+    def handle_options(argv) # :nodoc:
+      set_default_options
 
       OptionParser.new do |opts|
         opts.banner = "#{Rake.application.name} [-f rakefile] {options} targets..."
@@ -634,7 +635,7 @@ def handle_options # :nodoc:
 
         standard_rake_options.each { |args| opts.on(*args) }
         opts.environment("RAKEOPT")
-      end.parse(ARGV)
+      end.parse(argv)
     end
 
     # Similar to the regular Ruby +require+ command, but will check
@@ -782,5 +783,28 @@ def rakefile_location(backtrace=caller) # :nodoc:
       backtrace.find { |str| str =~ re } || ""
     end
 
+    def set_default_options
+      options.always_multitask           = false
+      options.backtrace                  = false
+      options.build_all                  = false
+      options.dryrun                     = false
+      options.ignore_deprecate           = false
+      options.ignore_system              = false
+      options.job_stats                  = false
+      options.load_system                = false
+      options.nosearch                   = false
+      options.rakelib                    = %w[rakelib]
+      options.show_all_tasks             = false
+      options.show_prereqs               = false
+      options.show_task_pattern          = nil
+      options.show_tasks                 = nil
+      options.silent                     = false
+      options.suppress_backtrace_pattern = nil
+      options.thread_pool_size           = Rake.suggested_thread_count
+      options.trace                      = false
+      options.trace_output               = $stderr
+      options.trace_rules                = false
+    end
+
   end
 end
diff --git a/lib/rake/rake_module.rb b/lib/rake/rake_module.rb
index f5cfde58a..03c295624 100644
--- a/lib/rake/rake_module.rb
+++ b/lib/rake/rake_module.rb
@@ -34,6 +34,34 @@ def add_rakelib(*files)
       application.options.rakelib ||= []
       application.options.rakelib.concat(files)
     end
+
+    # Make +block_application+ the default rake application inside a block so
+    # you can load rakefiles into a different application.
+    #
+    # This is useful when you want to run rake tasks inside a library without
+    # running rake in a sub-shell.
+    #
+    # Example:
+    #
+    #   Dir.chdir 'other/directory'
+    #
+    #   other_rake = Rake.with_application do |rake|
+    #     rake.load_rakefile
+    #   end
+    #
+    #   puts other_rake.tasks
+
+    def with_application(block_application = Rake::Application.new)
+      orig_application = Rake.application
+
+      Rake.application = block_application
+
+      yield block_application
+
+      block_application
+    ensure
+      Rake.application = orig_application
+    end
   end
 
 end
diff --git a/test/test_rake_application.rb b/test/test_rake_application.rb
index 141dd576f..456f7d878 100644
--- a/test/test_rake_application.rb
+++ b/test/test_rake_application.rb
@@ -10,11 +10,34 @@ def setup
     @app.options.rakelib = []
   end
 
-  def setup_command_line(*options)
-    ARGV.clear
-    options.each do |option|
-      ARGV << option
+  def test_class_with_application
+    orig_app = Rake.application
+
+    return_app = Rake.with_application do |yield_app|
+      refute_equal orig_app, yield_app, 'new application must be yielded'
+
+      assert_equal yield_app, Rake.application,
+                   'new application must be default in block'
+    end
+
+    refute_equal orig_app, return_app, 'new application not returned'
+    assert_equal orig_app, Rake.application, 'original application not default'
+  end
+
+  def test_class_with_application_user_defined
+    orig_app = Rake.application
+
+    user_app = Rake::Application.new
+
+    return_app = Rake.with_application user_app do |yield_app|
+      assert_equal user_app, yield_app, 'user application must be yielded'
+
+      assert_equal user_app, Rake.application,
+                   'user application must be default in block'
     end
+
+    assert_equal user_app, return_app, 'user application not returned'
+    assert_equal orig_app, Rake.application, 'original application not default'
   end
 
   def test_display_exception_details
@@ -26,6 +49,8 @@ def test_display_exception_details
     end
 
     out, err = capture_io do
+      @app.set_default_options # reset trace output IO
+
       @app.display_error_message ex
     end
 
@@ -42,6 +67,8 @@ def test_display_exception_details_bad_encoding
     end
 
     out, err = capture_io do
+      @app.set_default_options # reset trace output IO
+
       @app.display_error_message ex
     end
 
@@ -63,6 +90,8 @@ def test_display_exception_details_cause
     end
 
     out, err = capture_io do
+      @app.set_default_options # reset trace output IO
+
       @app.display_error_message ex
     end
 
@@ -187,7 +216,7 @@ def test_load_rakefile
     rakefile_unittest
 
     @app.instance_eval do
-      handle_options
+      handle_options []
       options.silent = true
       load_rakefile
     end
@@ -215,7 +244,7 @@ def test_load_rakefile_from_subdir
     Dir.chdir "subdir"
 
     @app.instance_eval do
-      handle_options
+      handle_options []
       options.silent = true
       load_rakefile
     end
@@ -246,7 +275,7 @@ def test_load_rakefile_doesnt_print_rakefile_directory_from_subdir_if_silent
 
     _, err = capture_io do
       @app.instance_eval do
-        handle_options
+        handle_options []
         options.silent = true
         raw_load_rakefile
       end
@@ -258,12 +287,11 @@ def test_load_rakefile_doesnt_print_rakefile_directory_from_subdir_if_silent
   def test_load_rakefile_not_found
     skip if jruby9?
 
-    ARGV.clear
     Dir.chdir @tempdir
     ENV["RAKE_SYSTEM"] = "not_exist"
 
     @app.instance_eval do
-      handle_options
+      handle_options []
       options.silent = true
     end
 
@@ -280,7 +308,7 @@ def test_load_from_system_rakefile
     rake_system_dir
 
     @app.instance_eval do
-      handle_options
+      handle_options []
       options.silent = true
       options.load_system = true
       options.rakelib = []
@@ -302,7 +330,7 @@ def @app.standard_system_dir
     ENV["RAKE_SYSTEM"] = nil
 
     @app.instance_eval do
-      handle_options
+      handle_options []
       options.silent = true
       options.load_system = true
       options.rakelib = []
@@ -362,28 +390,22 @@ def test_building_imported_files_on_demand
   def test_handle_options_should_not_strip_options_from_argv
     assert !@app.options.trace
 
-    valid_option = "--trace"
-    setup_command_line(valid_option)
-
-    @app.handle_options
+    argv = %w[--trace]
+    @app.handle_options argv
 
-    assert ARGV.include?(valid_option)
+    assert_includes argv, '--trace'
     assert @app.options.trace
   end
 
   def test_handle_options_trace_default_is_stderr
-    setup_command_line("--trace")
-
-    @app.handle_options
+    @app.handle_options %w[--trace]
 
     assert_equal STDERR, @app.options.trace_output
     assert @app.options.trace
   end
 
   def test_handle_options_trace_overrides_to_stdout
-    setup_command_line("--trace=stdout")
-
-    @app.handle_options
+    @app.handle_options %w[--trace=stdout]
 
     assert_equal STDOUT, @app.options.trace_output
     assert @app.options.trace
@@ -392,18 +414,16 @@ def test_handle_options_trace_overrides_to_stdout
   def test_handle_options_trace_does_not_eat_following_task_names
     assert !@app.options.trace
 
-    setup_command_line("--trace", "sometask")
+    argv = %w[--trace sometask]
+    @app.handle_options argv
 
-    @app.handle_options
-    assert ARGV.include?("sometask")
+    assert argv.include?("sometask")
     assert @app.options.trace
   end
 
   def test_good_run
     ran = false
 
-    ARGV << '--rakelib=""'
-
     @app.options.silent = true
 
     @app.instance_eval do
@@ -413,7 +433,7 @@ def test_good_run
     rakefile_default
 
     out, err = capture_io do
-      @app.run
+      @app.run %w[--rakelib=""]
     end
 
     assert ran
@@ -423,10 +443,9 @@ def test_good_run
 
   def test_display_task_run
     ran = false
-    setup_command_line("-f", "-s", "--tasks", '--rakelib=""')
     @app.last_description = "COMMENT"
     @app.define_task(Rake::Task, "default")
-    out, = capture_io { @app.run }
+    out, = capture_io { @app.run %w[-f -s --tasks --rakelib=""] }
     assert @app.options.show_tasks
     assert ! ran
     assert_match(/rake default/, out)
@@ -435,13 +454,12 @@ def test_display_task_run
 
   def test_display_prereqs
     ran = false
-    setup_command_line("-f", "-s", "--prereqs", '--rakelib=""')
     @app.last_description = "COMMENT"
     t = @app.define_task(Rake::Task, "default")
     t.enhance([:a, :b])
     @app.define_task(Rake::Task, "a")
     @app.define_task(Rake::Task, "b")
-    out, = capture_io { @app.run }
+    out, = capture_io { @app.run %w[-f -s --prereqs --rakelib=""] }
     assert @app.options.show_prereqs
     assert ! ran
     assert_match(/rake a$/, out)
@@ -451,37 +469,29 @@ def test_display_prereqs
 
   def test_bad_run
     @app.intern(Rake::Task, "default").enhance { fail }
-    setup_command_line("-f", "-s",  '--rakelib=""')
     _, err = capture_io {
-      assert_raises(SystemExit) { @app.run }
+      assert_raises(SystemExit) { @app.run %w[-f -s --rakelib=""]}
     }
     assert_match(/see full trace/i, err)
-  ensure
-    ARGV.clear
   end
 
   def test_bad_run_with_trace
     @app.intern(Rake::Task, "default").enhance { fail }
-    setup_command_line("-f", "-s", "-t")
     _, err = capture_io {
-      assert_raises(SystemExit) { @app.run }
+      @app.set_default_options
+      assert_raises(SystemExit) { @app.run %w[-f -s -t] }
     }
     refute_match(/see full trace/i, err)
-  ensure
-    ARGV.clear
   end
 
   def test_bad_run_with_backtrace
     @app.intern(Rake::Task, "default").enhance { fail }
-    setup_command_line("-f", "-s", "--backtrace")
     _, err = capture_io {
       assert_raises(SystemExit) {
-        @app.run
+        @app.run %w[-f -s --backtrace]
       }
     }
     refute_match(/see full trace/, err)
-  ensure
-    ARGV.clear
   end
 
   CustomError = Class.new(RuntimeError)
@@ -490,10 +500,9 @@ def test_bad_run_includes_exception_name
     @app.intern(Rake::Task, "default").enhance {
       raise CustomError, "intentional"
     }
-    setup_command_line("-f", "-s")
     _, err = capture_io {
       assert_raises(SystemExit) {
-        @app.run
+        @app.run %w[-f -s]
       }
     }
     assert_match(/CustomError: intentional/, err)
@@ -503,10 +512,9 @@ def test_rake_error_excludes_exception_name
     @app.intern(Rake::Task, "default").enhance {
       fail "intentional"
     }
-    setup_command_line("-f", "-s")
     _, err = capture_io {
       assert_raises(SystemExit) {
-        @app.run
+        @app.run %w[-f -s]
       }
     }
    refute_match(/RuntimeError/, err)
@@ -527,28 +535,22 @@ def test_printing_original_exception_cause
         raise custom_error, "Secondary Error"
       end
     }
-    setup_command_line("-f", "-s")
     _ ,err = capture_io {
       assert_raises(SystemExit) {
-        @app.run
+        @app.run %w[-f -s]
       }
     }
     if cause_supported?
       assert_match(/Original Error/, err)
     end
     assert_match(/Secondary Error/, err)
-  ensure
-    ARGV.clear
   end
 
   def test_run_with_bad_options
     @app.intern(Rake::Task, "default").enhance { fail }
-    setup_command_line("-f", "-s", "--xyzzy")
     assert_raises(SystemExit) {
-      capture_io { @app.run }
+      capture_io { @app.run %w[-f -s --xyzzy] }
     }
-  ensure
-    ARGV.clear
   end
 
   def test_standard_exception_handling_invalid_option
@@ -568,6 +570,8 @@ def test_standard_exception_handling_invalid_option
 
   def test_standard_exception_handling_other
     out, err = capture_io do
+      @app.set_default_options # reset trace output IO
+
       e = assert_raises SystemExit do
         @app.standard_exception_handling do
           raise "blah"
diff --git a/test/test_rake_application_options.rb b/test/test_rake_application_options.rb
index b34c2f634..d774678b6 100644
--- a/test/test_rake_application_options.rb
+++ b/test/test_rake_application_options.rb
@@ -9,7 +9,6 @@ def setup
     super
 
     @testkey = ENV["TESTKEY"]
-    clear_argv
     Rake::FileUtilsExt.verbose_flag = false
     Rake::FileUtilsExt.nowrite_flag = false
     TESTING_REQUIRE.clear
@@ -17,32 +16,27 @@ def setup
 
   def teardown
     ENV["TESTKEY"] = @testkey
-    clear_argv
     Rake::FileUtilsExt.verbose_flag = false
     Rake::FileUtilsExt.nowrite_flag = false
 
     super
   end
 
-  def clear_argv
-    ARGV.pop until ARGV.empty?
-  end
-
   def test_default_options
     opts = command_line
-    assert_nil opts.backtrace
-    assert_nil opts.dryrun
-    assert_nil opts.ignore_system
-    assert_nil opts.load_system
-    assert_nil opts.always_multitask
-    assert_nil opts.nosearch
+    assert_equal false, opts.backtrace
+    assert_equal false, opts.dryrun
+    assert_equal false, opts.ignore_system
+    assert_equal false, opts.load_system
+    assert_equal false, opts.always_multitask
+    assert_equal false, opts.nosearch
     assert_equal ["rakelib"], opts.rakelib
-    assert_nil opts.show_prereqs
+    assert_equal false, opts.show_prereqs
     assert_nil opts.show_task_pattern
     assert_nil opts.show_tasks
-    assert_nil opts.silent
-    assert_nil opts.trace
-    assert_nil opts.thread_pool_size
+    assert_equal false, opts.silent
+    assert_equal false, opts.trace
+    assert_equal Rake.suggested_thread_count, opts.thread_pool_size
     assert_equal ["rakelib"], opts.rakelib
     assert ! Rake::FileUtilsExt.verbose_flag
     assert ! Rake::FileUtilsExt.nowrite_flag
@@ -115,7 +109,7 @@ def test_help
 
   def test_jobs
     flags([]) do |opts|
-      assert_nil opts.thread_pool_size
+      assert_equal Rake.suggested_thread_count, opts.thread_pool_size
     end
     flags(["--jobs", "0"], ["-j", "0"]) do |opts|
       assert_equal 0, opts.thread_pool_size
@@ -329,12 +323,12 @@ def test_tasks
     flags("--tasks", "-T") do |opts|
       assert_equal :tasks, opts.show_tasks
       assert_equal(//.to_s, opts.show_task_pattern.to_s)
-      assert_nil opts.show_all_tasks
+      assert_equal false, opts.show_all_tasks
     end
     flags(["--tasks", "xyz"], ["-Txyz"]) do |opts|
       assert_equal :tasks, opts.show_tasks
       assert_equal(/xyz/.to_s, opts.show_task_pattern.to_s)
-      assert_nil opts.show_all_tasks
+      assert_equal false, opts.show_all_tasks
     end
     flags(["--tasks", "xyz", "--comments"]) do |opts|
       assert_equal :tasks, opts.show_tasks
@@ -445,8 +439,6 @@ def test_rake_explicit_task_library
 
   def flags(*sets)
     sets.each do |set|
-      ARGV.clear
-
       @exit = catch(:system_exit) { command_line(*set) }
 
       yield(@app.options) if block_given?
@@ -454,13 +446,12 @@ def flags(*sets)
   end
 
   def command_line(*options)
-    options.each do |opt| ARGV << opt end
     @app = Rake::Application.new
     def @app.exit(*args)
       throw :system_exit, :exit
     end
     @app.instance_eval do
-      args = handle_options
+      args = handle_options options
       collect_command_line_tasks(args)
     end
     @tasks = @app.top_level_tasks
diff --git a/test/test_rake_task.rb b/test/test_rake_task.rb
index b2bbb6d95..8bfdedb4e 100644
--- a/test/test_rake_task.rb
+++ b/test/test_rake_task.rb
@@ -62,10 +62,14 @@ def test_invoke_with_circular_dependencies
   end
 
   def test_dry_run_prevents_actions
-    Rake.application.options.dryrun = true
     runlist = []
     t1 = task(:t1) { |t| runlist << t.name; 3321 }
-    _, err = capture_io { t1.invoke }
+    _, err = capture_io {
+      Rake.application.set_default_options # reset trace output IO
+      Rake.application.options.dryrun = true
+
+      t1.invoke
+    }
     assert_match(/execute .*t1/i, err)
     assert_match(/dry run/i, err)
     refute_match(/invoke/i, err)
@@ -75,9 +79,11 @@ def test_dry_run_prevents_actions
   end
 
   def test_tasks_can_be_traced
-    Rake.application.options.trace = true
     t1 = task(:t1)
     _, err = capture_io {
+      Rake.application.set_default_options # reset trace output IO
+      Rake.application.options.trace = true
+
       t1.invoke
     }
     assert_match(/invoke t1/i, err)
diff --git a/test/test_rake_task_argument_parsing.rb b/test/test_rake_task_argument_parsing.rb
index e34126591..fc494a463 100644
--- a/test/test_rake_task_argument_parsing.rb
+++ b/test/test_rake_task_argument_parsing.rb
@@ -96,16 +96,14 @@ def @app.unix?() raise end
   end
 
   def test_no_rakeopt
-    ARGV << "--trace"
     app = Rake::Application.new
-    app.init
+    app.init %w[--trace]
     assert !app.options.silent
   end
 
   def test_rakeopt_with_blank_options
-    ARGV << "--trace"
     app = Rake::Application.new
-    app.init
+    app.init %w[--trace]
     assert !app.options.silent
   end
 
diff --git a/test/test_rake_win32.rb b/test/test_rake_win32.rb
index 292af4715..6c341f486 100644
--- a/test/test_rake_win32.rb
+++ b/test/test_rake_win32.rb
@@ -65,7 +65,11 @@ def test_win32_backtrace_with_different_case
     rake.options.trace = true
     rake.instance_variable_set(:@rakefile, "Rakefile")
 
-    _, err = capture_io { rake.display_error_message(ex) }
+    _, err = capture_io {
+      rake.set_default_options # reset trace output IO
+
+      rake.display_error_message(ex)
+    }
 
     assert_match(/rakefile/, err)
   end