diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
index 39d7329..8996a89 100644
--- a/.github/workflows/ruby.yml
+++ b/.github/workflows/ruby.yml
@@ -32,7 +32,19 @@ jobs:
           ruby-version: ${{ matrix.ruby-version }}
           bundler-cache: true # runs 'bundle install' and caches installed gems automatically
           bundler-args: --without development
-      - name: Run Rubocop
-        run: bundle exec rubocop
       - name: Quickdraw tests
-        run: bundle exec qt
+        run: bundle exec qt -t 1
+  rubocop:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        ruby-version: ['3.3']
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby-version }}
+          bundler-cache: true
+      - name: Run RuboCop
+        run: bundle exec rubocop
diff --git a/.gitignore b/.gitignore
index b82c8cc..4a3cda5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,4 @@
 .rubocop-*
 .DS_Store
 .covered.db
+Gemfile.lock
diff --git a/Gemfile b/Gemfile
index 45b1cef..2f11e94 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,10 +5,13 @@ source "https://rubygems.org"
 # Specify your gem's dependencies in quickdraw.gemspec
 gemspec
 
-group :development do
-	gem "rubocop"
-	gem "rspec-expectations"
-	gem "minitest"
-	gem "sus"
-	gem "covered"
+gem "rspec-expectations"
+
+if RUBY_ENGINE == "ruby"
+	group :development do
+		gem "rubocop"
+		gem "minitest"
+		gem "sus"
+		gem "covered"
+	end
 end
diff --git a/Gemfile.lock b/Gemfile.lock
deleted file mode 100644
index 197263e..0000000
--- a/Gemfile.lock
+++ /dev/null
@@ -1,73 +0,0 @@
-PATH
-  remote: .
-  specs:
-    quickdraw (0.1.0)
-
-GEM
-  remote: https://rubygems.org/
-  specs:
-    ast (2.4.2)
-    console (1.23.6)
-      fiber-annotation
-      fiber-local
-      json
-    covered (0.25.1)
-      console (~> 1.0)
-      msgpack (~> 1.0)
-    diff-lcs (1.5.1)
-    fiber-annotation (0.2.0)
-    fiber-local (1.0.0)
-    json (2.7.2)
-    json (2.7.2-java)
-    language_server-protocol (3.17.0.3)
-    minitest (5.22.3)
-    msgpack (1.7.2)
-    msgpack (1.7.2-java)
-    parallel (1.25.1)
-    parser (3.3.3.0)
-      ast (~> 2.4.1)
-      racc
-    racc (1.8.0)
-    racc (1.8.0-java)
-    rainbow (3.1.1)
-    regexp_parser (2.9.2)
-    rexml (3.3.0)
-      strscan
-    rspec-expectations (3.13.0)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.13.0)
-    rspec-support (3.13.1)
-    rubocop (1.64.1)
-      json (~> 2.3)
-      language_server-protocol (>= 3.17.0)
-      parallel (~> 1.10)
-      parser (>= 3.3.0.2)
-      rainbow (>= 2.2.2, < 4.0)
-      regexp_parser (>= 1.8, < 3.0)
-      rexml (>= 3.2.5, < 4.0)
-      rubocop-ast (>= 1.31.1, < 2.0)
-      ruby-progressbar (~> 1.7)
-      unicode-display_width (>= 2.4.0, < 3.0)
-    rubocop-ast (1.31.3)
-      parser (>= 3.3.1.0)
-    ruby-progressbar (1.13.0)
-    strscan (3.1.0)
-    strscan (3.1.0-java)
-    sus (0.24.6)
-    unicode-display_width (2.5.0)
-
-PLATFORMS
-  arm64-darwin
-  universal-java-11
-  x86_64-linux
-
-DEPENDENCIES
-  covered
-  minitest
-  quickdraw!
-  rspec-expectations
-  rubocop
-  sus
-
-BUNDLED WITH
-   2.4.6
diff --git a/lib/quickdraw.rb b/lib/quickdraw.rb
index 85e3e57..dbb0720 100644
--- a/lib/quickdraw.rb
+++ b/lib/quickdraw.rb
@@ -1,5 +1,9 @@
 # frozen_string_literal: true
 
+require "concurrent/map"
+require "concurrent/array"
+require "concurrent/set"
+
 module Quickdraw
 	autoload :ArgumentError, "quickdraw/errors/argument_error"
 	autoload :CLI, "quickdraw/cli"
@@ -26,6 +30,7 @@ module Quickdraw
 	Null = Object.new.freeze
 	Error = Module.new
 	Config = Configuration.new
+	MATCHERS = Concurrent::Map.new
 
 	def self.configure(&)
 		yield Config
diff --git a/lib/quickdraw/concurrent_array.rb b/lib/quickdraw/concurrent_array.rb
deleted file mode 100644
index f63f2e4..0000000
--- a/lib/quickdraw/concurrent_array.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-# frozen_string_literal: true
-
-class Quickdraw::ConcurrentArray
-	def initialize
-		@mutex = Mutex.new
-		@array = []
-	end
-
-	def <<(element)
-		@mutex.synchronize { @array << element }
-	end
-
-	def to_a
-		@array.dup
-	end
-
-	def size
-		@array.size
-	end
-end
diff --git a/lib/quickdraw/context.rb b/lib/quickdraw/context.rb
index 12835ef..4a640f6 100644
--- a/lib/quickdraw/context.rb
+++ b/lib/quickdraw/context.rb
@@ -9,6 +9,8 @@ def test(name = nil, skip: false, &block)
 		end
 
 		def use(*new_matchers)
+			matchers = self.matchers
+
 			i = 0
 			number_of_new_matchers = new_matchers.size
 
@@ -19,10 +21,12 @@ def use(*new_matchers)
 		end
 
 		def matchers
-			@matchers ||= if superclass < Quickdraw::Context
-				superclass.matchers.dup
-			else
-				Set[]
+			Quickdraw::MATCHERS.fetch_or_store(self) do
+				if superclass < Quickdraw::Context
+					superclass.matchers.dup
+				else
+					Concurrent::Set.new
+				end
 			end
 		end
 
@@ -39,7 +43,7 @@ def initialize(name, skip, runner, matchers)
 		@runner = runner
 		@matchers = matchers
 
-		@expectations = []
+		@expectations = Concurrent::Array.new
 	end
 
 	def expect(value = Quickdraw::Null, &block)
diff --git a/lib/quickdraw/map.rb b/lib/quickdraw/map.rb
deleted file mode 100644
index 7b6e953..0000000
--- a/lib/quickdraw/map.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-# frozen_string_literal: true
-
-class Quickdraw::Map
-	include Enumerable
-
-	def initialize
-		@hash = {}
-		@mutex = Mutex.new
-	end
-
-	def [](value)
-		@hash[value]
-	end
-
-	def []=(key, value)
-		@mutex.synchronize do
-			@hash[key] = value
-		end
-	end
-
-	def each(&)
-		@hash.each(&)
-	end
-
-	def clear
-		@mutex.synchronize do
-			@hash.clear
-		end
-	end
-end
diff --git a/lib/quickdraw/registry.rb b/lib/quickdraw/registry.rb
index 062158b..47f8836 100644
--- a/lib/quickdraw/registry.rb
+++ b/lib/quickdraw/registry.rb
@@ -2,9 +2,9 @@
 
 class Quickdraw::Registry
 	def initialize
-		@registered_matchers = Quickdraw::Map.new
-		@type_matchers = Quickdraw::Map.new
-		@shapes = Quickdraw::Map.new
+		@registered_matchers = Concurrent::Map.new
+		@type_matchers = Concurrent::Map.new
+		@shapes = Concurrent::Map.new
 	end
 
 	# Register a new matcher for the given types.
@@ -32,15 +32,19 @@ def expectation_for(value, matchers: nil)
 
 	# A "shape" is a specialised Expectation class that includes the given matchers. It's cached against the list of matchers.
 	def shape_for(matchers)
-		@shapes[matchers] ||= Class.new(Quickdraw::Expectation) do
-			matchers.each { |m| include m }
-			freeze
+		@shapes.fetch_or_store(matchers) do
+			Class.new(Quickdraw::Expectation) do
+				matchers.each { |m| include m }
+				freeze
+			end
 		end
 	end
 
 	# Given a value, find all the matchers that match it. This is cached against the class of the value.
 	def matchers_for(value)
-		@type_matchers[value.class] ||= slowly_find_matchers_for(value)
+		@type_matchers.fetch_or_store(value.class) do
+			slowly_find_matchers_for(value)
+		end
 	end
 
 	# If the above has a cache miss, we'll need to find the correct matchers slowly and then cache them.
diff --git a/lib/quickdraw/run.rb b/lib/quickdraw/run.rb
index 77831ab..a19d32e 100644
--- a/lib/quickdraw/run.rb
+++ b/lib/quickdraw/run.rb
@@ -72,7 +72,7 @@ def load_tests
 	end
 
 	def batch_tests
-		batches = Array.new([@processes, @tests.size].min) { Quickdraw::Queue.new }
+		batches = Array.new([@processes, @tests.size].min) { Concurrent::Array.new }
 
 		number_of_tests = @tests.size
 		i = 0
@@ -111,7 +111,7 @@ def fork_processes
 	end
 
 	def run_inline
-		queue = Quickdraw::Queue.new
+		queue = Concurrent::Array.new
 
 		i = 0
 		number_of_tests = @tests.size
diff --git a/lib/quickdraw/runner.rb b/lib/quickdraw/runner.rb
index db98d7c..dad6c12 100644
--- a/lib/quickdraw/runner.rb
+++ b/lib/quickdraw/runner.rb
@@ -7,8 +7,8 @@ def initialize(queue:, threads:)
 		@queue = queue
 		@threads = threads
 
-		@failures = Quickdraw::ConcurrentArray.new
-		@successes = Quickdraw::ConcurrentArray.new
+		@failures = Concurrent::Array.new
+		@successes = Concurrent::Array.new
 	end
 
 	def call
@@ -47,8 +47,13 @@ def failure!
 	private
 
 	def drain_queue
-		@queue.drain { |(name, skip, test, context)|
+		queue = @queue
+		next_item = queue.shift
+
+		while next_item
+			name, skip, test, context = next_item
 			context.run_test(name, skip, self, &test)
-		}
+			next_item = queue.shift
+		end
 	end
 end
diff --git a/quickdraw.gemspec b/quickdraw.gemspec
index 43e03cc..b5c6ad8 100644
--- a/quickdraw.gemspec
+++ b/quickdraw.gemspec
@@ -30,6 +30,8 @@ Gem::Specification.new do |spec|
 	spec.executables = spec.files.grep(%r{\Aexe/}) { |f| File.basename(f) }
 	spec.require_paths = ["lib"]
 
+	spec.add_runtime_dependency "concurrent-ruby"
+
 	# For more information and examples about making a new gem, check out our
 	# guide at: https://bundler.io/guides/creating_gem.html
 	spec.metadata["rubygems_mfa_required"] = "true"