Increase test coverage in constraints_test and `backup_and_restore_…

…callback_test` (#18639)

* Add more tests to `constraints_test`

* Add tests to `backup_and_restore_callback_test`

keras/callbacks/backup_and_restore_callback_test.py

@@ -167,3 +167,15 @@ def test_model_deleted_case_epoch(self):
             verbose=0,
         )
         self.assertFalse(file_utils.exists(backup_dir))
+
+    def test_backup_dir_empty_error(self):
+        with self.assertRaisesRegex(
+            ValueError, expected_regex="Empty `backup_dir` argument passed"
+        ):
+            callbacks.BackupAndRestore(backup_dir="", save_freq="epoch")
+
+    def test_backup_dir_none_error(self):
+        with self.assertRaisesRegex(
+            ValueError, expected_regex="Empty `backup_dir` argument passed"
+        ):
+            callbacks.BackupAndRestore(backup_dir=None, save_freq="epoch")

keras/constraints/constraints_test.py

@@ -57,3 +57,45 @@ def test_get_method(self):
 
         with self.assertRaises(ValueError):
             constraints.get("typo")
+
+    def test_default_constraint_call(self):
+        constraint_fn = constraints.Constraint()
+        x = np.array([1.0, 2.0, 3.0])
+        output = constraint_fn(x)
+        self.assertAllClose(x, output)
+
+    def test_constraint_get_config(self):
+        constraint_fn = constraints.Constraint()
+        config = constraint_fn.get_config()
+        self.assertEqual(config, {})
+
+    def test_constraint_from_config(self):
+        constraint_fn = constraints.Constraint()
+        config = constraint_fn.get_config()
+        recreated_constraint_fn = constraints.Constraint.from_config(config)
+        self.assertIsInstance(recreated_constraint_fn, constraints.Constraint)
+
+    def test_max_norm_get_config(self):
+        constraint_fn = constraints.MaxNorm(max_value=3.0, axis=1)
+        config = constraint_fn.get_config()
+        expected_config = {"max_value": 3.0, "axis": 1}
+        self.assertEqual(config, expected_config)
+
+    def test_unit_norm_get_config(self):
+        constraint_fn = constraints.UnitNorm(axis=1)
+        config = constraint_fn.get_config()
+        expected_config = {"axis": 1}
+        self.assertEqual(config, expected_config)
+
+    def test_min_max_norm_get_config(self):
+        constraint_fn = constraints.MinMaxNorm(
+            min_value=0.5, max_value=2.0, rate=0.7, axis=1
+        )
+        config = constraint_fn.get_config()
+        expected_config = {
+            "min_value": 0.5,
+            "max_value": 2.0,
+            "rate": 0.7,
+            "axis": 1,
+        }
+        self.assertEqual(config, expected_config)