diff --git a/Guardfile b/Guardfile
index dab8842ab..6a8620807 100644
--- a/Guardfile
+++ b/Guardfile
@@ -2,33 +2,15 @@
 
 guard :bundler do
   watch('Gemfile')
-  watch('Gemfile.lock')
-  watch(%w{.+.gemspec\z})
 end
 
-guard :rspec, cli: File.read('.rspec').split.push('--fail-fast').join(' '), keep_failed: false do
-  # Run all specs if configuration is modified
-  watch('.rspec')              { 'spec' }
-  watch('Guardfile')           { 'spec' }
-  watch('Gemfile.lock')        { 'spec' }
-  watch('spec/spec_helper.rb') { 'spec' }
+guard :rspec, :all_after_pass => false, :all_on_start => false, :cmd => 'bundle exec rspec --fail-fast --seed 0' do
+  # run all specs if the spec_helper or supporting files files are modified
+  watch('spec/spec_helper.rb')                      { 'spec/unit' }
+  watch(%r{\Aspec/(?:lib|support|shared)/.+\.rb\z}) { 'spec/unit' }
 
-  # Run all specs if supporting files files are modified
-  watch(%r{\Aspec/(?:fixtures|lib|support|shared)/.+\.rb\z}) { 'spec' }
+  watch(%r{lib/.*.rb})                              { 'spec/unit' }
 
-  # Run unit specs if associated lib code is modified
-  watch(%r{\Alib/(.+)\.rb\z})                                         { |m| Dir["spec/unit/#{m[1]}*"]         }
-  watch(%r{\Alib/(.+)/support/(.+)\.rb\z})                            { |m| Dir["spec/unit/#{m[1]}/#{m[2]}*"] }
-  watch("lib/#{File.basename(File.expand_path('../', __FILE__))}.rb") { 'spec'                                }
-
-  # Run a spec if it is modified
-  watch(%r{\Aspec/(?:unit|integration)/.+_spec\.rb\z})
+  # run a spec if it is modified
+  watch(%r{\Aspec/.+_spec\.rb\z})
 end
-
-# Deactivated for now. Somehow it disables the rspec guard.
-#
-# guard :rubocop, cli: %w[--config config/rubocop.yml] do
-#   watch(%r{.+\.(?:rb|rake)\z})
-#   watch(%r{\Aconfig/rubocop\.yml\z})  { |m| File.dirname(m[0]) }
-#   watch(%r{(?:.+/)?\.rubocop\.yml\z}) { |m| File.dirname(m[0]) }
-# end
diff --git a/lib/mutant.rb b/lib/mutant.rb
index 1f227620d..bedb762e7 100644
--- a/lib/mutant.rb
+++ b/lib/mutant.rb
@@ -32,6 +32,7 @@ module Mutant
 require 'mutant/singleton_methods'
 require 'mutant/constants'
 require 'mutant/random'
+require 'mutant/walker'
 require 'mutant/predicate'
 require 'mutant/predicate/attribute'
 require 'mutant/predicate/whitelist'
diff --git a/lib/mutant/cli.rb b/lib/mutant/cli.rb
index 105f06b02..f5ceab5c7 100644
--- a/lib/mutant/cli.rb
+++ b/lib/mutant/cli.rb
@@ -43,6 +43,7 @@ def self.run(arguments)
     def initialize(arguments = [])
       @filters, @matchers = [], []
       @debug = @fail_fast = @zombie = false
+      @expect_coverage = 100.0
       @strategy = Strategy::Null.new
       @cache = Mutant::Cache.new
       parse(arguments)
@@ -64,7 +65,8 @@ def config
         subject_predicate: @subject_predicate.output,
         strategy:          @strategy,
         fail_fast:         @fail_fast,
-        reporter:          reporter
+        reporter:          reporter,
+        expect_coverage:   @expect_coverage
       )
     end
     memoize :config