diff --git a/test/test_config.rb b/test/test_config.rb
index b478441813..73676bf49d 100644
--- a/test/test_config.rb
+++ b/test/test_config.rb
@@ -15,7 +15,6 @@ def test_default_max_threads
     assert_equal max_threads, Puma::Configuration.new.default_max_threads
   end
 
-
   def test_app_from_rackup
     conf = Puma::Configuration.new do |c|
       c.rackup "test/rackup/hello-bind.ru"
@@ -59,19 +58,6 @@ def test_ssl_configuration_from_DSL
     assert_equal [200, {}, ["embedded app"]], app.call({})
   end
 
-  def test_custom_logger_from_DSL
-    conf = Puma::Configuration.new do |c|
-      c.load "test/config/custom_logger.rb"
-    end
-
-    conf.load
-    out, _ = capture_subprocess_io do
-      conf.options[:logger].write('test')
-    end
-
-    assert_match /Custom logging: test/, out
-  end
-
   def test_ssl_bind
     skip_if :jruby
     skip_unless :ssl
@@ -423,6 +409,18 @@ def assert_run_hooks(hook_name, options = {})
   end
 end
 
+# contains tests that cannot run parallel
+class TestConfigFileSingle < TestConfigFileBase
+  def test_custom_logger_from_DSL
+    conf = Puma::Configuration.new { |c| c.load 'test/config/custom_logger.rb' }
+
+    conf.load
+    out, _ = capture_subprocess_io { conf.options[:logger].write 'test' }
+
+    assert_equal 'Custom logging: test', out
+  end
+end
+
 # Thread unsafe modification of ENV
 class TestEnvModifificationConfig < TestConfigFileBase
   def test_double_bind_port
diff --git a/test/test_thread_pool.rb b/test/test_thread_pool.rb
index c6ffc0a68f..77c9383767 100644
--- a/test/test_thread_pool.rb
+++ b/test/test_thread_pool.rb
@@ -63,10 +63,10 @@ def test_thread_name
   end
 
   def test_thread_name_linux
-    skip 'Thread.name not supported' unless Thread.current.respond_to?(:name)
+    skip 'Thread.name not supported' unless Thread.current.respond_to?(:name) && Puma::IS_MRI
 
     task_dir = File.join('', 'proc', Process.pid.to_s, 'task')
-    skip 'This test only works under Linux with appropriate permissions' if !(File.directory?(task_dir) && File.readable?(task_dir))
+    skip 'This test only works under Linux and MRI Ruby with appropriate permissions' if !(File.directory?(task_dir) && File.readable?(task_dir)) && Puma::IS_MRI
 
     expected_thread_name = 'puma tst tp 001'
     found_thread = false