pythonGH-89812: Test that pathlib.Path.is_junction() returns false

Slightly expand the test coverage of `is_junction()`. The existing test
only checks that `os.path.isjunction()` is called under-the-hood.

Lib/test/test_pathlib.py

@@ -2239,6 +2239,15 @@ def test_is_symlink(self):
             self.assertIs((P / 'linkA\udfff').is_file(), False)
             self.assertIs((P / 'linkA\x00').is_file(), False)
 
+    def test_is_junction_false(self):
+        P = self.cls(BASE)
+        self.assertFalse((P / 'fileA').is_junction())
+        self.assertFalse((P / 'dirA').is_junction())
+        self.assertFalse((P / 'non-existing').is_junction())
+        self.assertFalse((P / 'fileA' / 'bah').is_junction())
+        self.assertFalse((P / 'fileA\udfff').is_junction())
+        self.assertFalse((P / 'fileA\x00').is_junction())
+
     def test_is_fifo_false(self):
         P = self.cls(BASE)
         self.assertFalse((P / 'fileA').is_fifo())