Add specs for Process::Status#>>

They're pretty minimal, since the method is deprecated and will be
removed in Ruby 3.5. (Ruby 3.3 warns for removal in 3.4, but 3.4-dev
still has the method and warns for removal in 3.5)

core/process/status/right_shift_spec.rb

@@ -1,5 +1,34 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Status#>>" do
-  it "needs to be reviewed for spec completeness"
+  it "returns a right shift of the integer status of an exited child" do
+    suppress_warning do
+      ruby_exe("exit(29)", exit_status: 29)
+      ($? >> 0).should == $?.to_i
+      ($? >> 1).should == $?.to_i >> 1
+
+      # Actual value is implementation specific
+      platform_is :linux do
+        ($? >> 8).should == 29
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raises an ArgumentError if shift value is negative" do
+      suppress_warning do
+        ruby_exe("exit(0)")
+        -> {
+          $? >> -1
+        }.should raise_error(ArgumentError, 'negative shift value: -1')
+      end
+    end
+
+    it "shows a deprecation warning" do
+      ruby_exe("exit(0)")
+      -> {
+        $? >> 0
+      }.should complain(/warning: Process::Status#>> is deprecated and will be removed .*use other Process::Status attributes instead/)
+    end
+  end
 end