diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 016b288c19..d6340e489d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,10 +12,8 @@ jobs:
       fail-fast: false
       matrix:
         os:
-          - ubuntu-20.04
-          - ubuntu-18.04
-          - macos-11.0
-          - macos-10.15
+          - ubuntu-latest
+          - macos-latest
           - windows-latest
         ruby:
           - '2.4'
@@ -26,11 +24,15 @@ jobs:
           - '3.1'
           - debug
           - jruby-head
+          - truffleruby
+          - truffleruby-head
         include:
           - { os: windows-latest , ruby: mingw }
           - { os: windows-latest , ruby: mswin }
         exclude:
           - { os: windows-latest , ruby: debug }
+          - { os: windows-latest , ruby: truffleruby }
+          - { os: windows-latest , ruby: truffleruby-head }
 
     steps:
       - uses: actions/checkout@v2
@@ -73,3 +75,7 @@ jobs:
       - run: bundle exec rake test
 
       - run: gem install --verbose --backtrace pkg/*.gem
+
+      - name: Run tests on the installed gem
+        run: ruby run-test.rb
+        if: matrix.ruby != '2.4' # strscan is a default gem from 2.5
diff --git a/Rakefile b/Rakefile
index b886d9a78d..dfd1a008ad 100644
--- a/Rakefile
+++ b/Rakefile
@@ -23,14 +23,17 @@ if RUBY_ENGINE == "jruby"
     ext.target_version = '1.8'
     ext.ext_dir = 'ext/java'
   end
-else
+elsif RUBY_ENGINE == "ruby"
   require 'rake/extensiontask'
   Rake::ExtensionTask.new("strscan")
+else
+  task :compile
 end
 
 desc "Run test"
 task :test do
-  ENV["RUBYOPT"] = "-Ilib -Itest/lib -rbundler/setup -rhelper"
+  require_path = RUBY_ENGINE == 'jruby' ? "lib/jruby" : "lib"
+  ENV["RUBYOPT"] = "-I#{require_path} -rbundler/setup"
   ruby("run-test.rb")
 end
 
diff --git a/ext/strscan/extconf.rb b/ext/strscan/extconf.rb
index f0ecbf85d8..b53b63e455 100644
--- a/ext/strscan/extconf.rb
+++ b/ext/strscan/extconf.rb
@@ -1,5 +1,9 @@
 # frozen_string_literal: true
 require 'mkmf'
-$INCFLAGS << " -I$(top_srcdir)" if $extmk
-have_func("onig_region_memsize", "ruby.h")
-create_makefile 'strscan'
+if RUBY_ENGINE == 'ruby'
+  $INCFLAGS << " -I$(top_srcdir)" if $extmk
+  have_func("onig_region_memsize", "ruby.h")
+  create_makefile 'strscan'
+else
+  File.write('Makefile', dummy_makefile("").join)
+end
diff --git a/lib/jruby/strscan.rb b/lib/jruby/strscan.rb
new file mode 100644
index 0000000000..4f796c25cd
--- /dev/null
+++ b/lib/jruby/strscan.rb
@@ -0,0 +1,2 @@
+require 'strscan.jar'
+JRuby::Util.load_ext("org.jruby.ext.strscan.StringScannerLibrary")
diff --git a/lib/strscan.rb b/lib/strscan.rb
deleted file mode 100644
index 19baccff26..0000000000
--- a/lib/strscan.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-if RUBY_ENGINE == 'jruby'
-  require 'strscan.jar'
-  JRuby::Util.load_ext("org.jruby.ext.strscan.StringScannerLibrary")
-else
-  require 'strscan.so'
-end
diff --git a/run-test.rb b/run-test.rb
index 4ccb024a6b..b4390272ad 100755
--- a/run-test.rb
+++ b/run-test.rb
@@ -1,8 +1,10 @@
 #!/usr/bin/env ruby
 
-$LOAD_PATH.unshift("test")
-$LOAD_PATH.unshift("test/lib")
-$LOAD_PATH.unshift("lib")
+require 'strscan'
+puts "Loaded strscan from #{$".grep(/\/strscan\./).join(', ')}"
+puts "Gem from #{Gem.loaded_specs["strscan"]&.full_gem_path}"
+
+require_relative 'test/lib/helper'
 
 Dir.glob("test/strscan/**/*test_*.rb") do |test_rb|
   require File.expand_path(test_rb)
diff --git a/strscan.gemspec b/strscan.gemspec
index 871636d86c..d59e645695 100644
--- a/strscan.gemspec
+++ b/strscan.gemspec
@@ -16,14 +16,13 @@ Gem::Specification.new do |s|
   s.summary = "Provides lexical scanning operations on a String."
   s.description = "Provides lexical scanning operations on a String."
 
-  s.require_path = %w{lib}
-
   jruby = true if Gem::Platform.new('java') =~ s.platform or RUBY_ENGINE == 'jruby'
-  
   if jruby
-    s.files = %w{lib/strscan.jar lib/strscan.rb}
+    s.require_paths = %w{lib/jruby lib}
+    s.files = %w{lib/strscan.jar lib/jruby/strscan.rb}
     s.platform = "java"
   else
+    s.require_paths = %w{lib}
     s.files = %w{ext/strscan/extconf.rb ext/strscan/strscan.c}
     s.extensions = %w{ext/strscan/extconf.rb}
   end
diff --git a/test/strscan/test_ractor.rb b/test/strscan/test_ractor.rb
index 480c1ae8a6..a5de7e56ed 100644
--- a/test/strscan/test_ractor.rb
+++ b/test/strscan/test_ractor.rb
@@ -3,7 +3,7 @@
 
 class TestStringScannerRactor < Test::Unit::TestCase
   def setup
-    pend unless defined? Ractor
+    omit "Ractor not defined" unless defined? Ractor
   end
 
   def test_ractor
diff --git a/test/strscan/test_stringscanner.rb b/test/strscan/test_stringscanner.rb
index 6e30be1f7d..b46b47bedd 100644
--- a/test/strscan/test_stringscanner.rb
+++ b/test/strscan/test_stringscanner.rb
@@ -207,6 +207,8 @@ def test_pos_unicode
   end
 
   def test_charpos_not_use_string_methods
+    omit "not supported on TruffleRuby" if RUBY_ENGINE == "truffleruby"
+
     string = +'abcädeföghi'
     scanner = create_string_scanner(string)
 
@@ -567,6 +569,8 @@ def test_encoding_string
   end
 
   def test_invalid_encoding_string
+    omit "no encoding check on TruffleRuby for scan(String)" if RUBY_ENGINE == "truffleruby"
+
     str = "\xA1\xA2".dup.force_encoding("euc-jp")
     ss = create_string_scanner(str)
     assert_raise(Encoding::CompatibilityError) do
@@ -712,6 +716,8 @@ def test_inspect2
   end
 
   def test_aref_without_regex
+    omit "#[:missing] always raises on TruffleRuby if matched" if RUBY_ENGINE == "truffleruby"
+
     s = create_string_scanner('abc')
     s.get_byte
     assert_nil(s[:c])