1 files changed, 24 insertions, 0 deletions
diff --git a/spec/ruby/core/process/_fork_spec.rb b/spec/ruby/core/process/_fork_spec.rb
new file mode 100644
index 0000000000..6f711ad2dd
--- /dev/null
+++ b/spec/ruby/core/process/_fork_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../spec_helper'
+
+ruby_version_is "3.1" do
+  describe "Process._fork" do
+    it "for #respond_to? returns the same as Process.respond_to?(:fork)" do
+      Process.respond_to?(:_fork).should == Process.respond_to?(:fork)
+    end
+
+    guard_not -> { Process.respond_to?(:fork) } do
+      it "raises a NotImplementedError when called" do
+        -> { Process._fork }.should raise_error(NotImplementedError)
+      end
+    end
+
+    guard -> { Process.respond_to?(:fork) } do
+      it "is called by Process#fork" do
+        Process.should_receive(:_fork).once.and_return(42)
+
+        pid = Process.fork {}
+        pid.should equal(42)
+      end
+    end
+  end
+end