1 files changed, 37 insertions, 0 deletions
diff --git a/spec/ruby/core/thread/native_thread_id_spec.rb b/spec/ruby/core/thread/native_thread_id_spec.rb
new file mode 100644
index 0000000000..17a08c8a15
--- /dev/null
+++ b/spec/ruby/core/thread/native_thread_id_spec.rb
@@ -0,0 +1,37 @@
+require_relative '../../spec_helper'
+
+ruby_version_is "3.1" do
+  platform_is :linux, :darwin, :windows, :freebsd do
+    describe "Thread#native_thread_id" do
+      it "returns an integer when the thread is alive" do
+        Thread.current.native_thread_id.should be_kind_of(Integer)
+      end
+
+      it "returns nil when the thread is not running" do
+        t = Thread.new {}
+        t.join
+        t.native_thread_id.should == nil
+      end
+
+      it "each thread has different native thread id" do
+        t = Thread.new { sleep }
+        Thread.pass until t.stop?
+        main_thread_id = Thread.current.native_thread_id
+        t_thread_id = t.native_thread_id
+
+        if ruby_version_is "3.3"
+          # native_thread_id can be nil on a M:N scheduler
+          t_thread_id.should be_kind_of(Integer) if t_thread_id != nil
+        else
+          t_thread_id.should be_kind_of(Integer)
+        end
+
+        main_thread_id.should_not == t_thread_id
+
+        t.run
+        t.join
+        t.native_thread_id.should == nil
+      end
+    end
+  end
+end