Update test script

test cd command error

test/test.py

@@ -161,7 +161,7 @@ class Test:
         _, std_stderr, _ = self._execute_shell_command(cmd)
 
         if not std_stderr:
-            raise AssertionError('The command {} should return an error but stderr is empty'.format(str_cmd))
+            raise AssertionError('The command "{}" should return an error but stderr is empty'.format(str_cmd))
 
 
     def test_foregroundjobs(self):
@@ -192,11 +192,17 @@ class Test:
 
     @test
     def test_builtin_cd(self):
+        # Test existing directory
         dir = tempfile.TemporaryDirectory()
         _, _, cwd = self._execute_shell_command(['cd', dir.name], cwd='.', timeout=1)
         if dir.name != cwd:
             raise AssertionError('Changing directory failed: the directory shouldbe {} but it is {}'.format(dir, cwd))
-        #TODO: test if the directory does not exist
+
+        # Test non-existing directory
+        cmd = ['cd', 'thisfoldershouldnotexist']
+        _, stderr, _ = self._execute_shell_command(cmd, timeout=1)
+        if not stderr:
+            raise AssertionError('The command "{}" should return an error but stderr is empty'.format(' '.join(cmd)))
 
 
     def test_builtin(self):