[Add] atleast_Nd as tensor method

python/paddle/tensor/__init__.py

@@ -734,6 +734,9 @@
     'normal_',
     'index_fill',
     'index_fill_',
+    'atleast_1d',
+    'atleast_2d',
+    'atleast_3d',
 ]
 
 # this list used in math_op_patch.py for magic_method bind

test/legacy_test/test_atleast_nd.py

@@ -413,7 +413,7 @@ def test_all(self):
     ),
 )
 class TestAtleastErrorCombineInputs(BaseTest):
-    """test combine inputs, like: `at_leastNd((x, y))`, where paddle treats like numpy, not pytorch"""
+    """test combine inputs, like: `at_leastNd((x, y))`, where paddle treats like numpy"""
 
     def test_all(self):
         with self.assertRaises(ValueError):
@@ -427,5 +427,32 @@ def test_all(self):
             )
 
 
+class TestAtleastAsTensorMethod(unittest.TestCase):
+    def test_as_tensor_method(self):
+        input = 123
+        tensor = paddle.to_tensor(input)
+
+        for place in PLACES:
+            paddle.disable_static(place)
+
+            out = tensor.atleast_1d()
+            out_ref = np.atleast_1d(input)
+
+            for n, p in zip(out_ref, out):
+                np.testing.assert_allclose(n, p.numpy(), rtol=RTOL, atol=ATOL)
+
+            out = tensor.atleast_2d()
+            out_ref = np.atleast_2d(input)
+
+            for n, p in zip(out_ref, out):
+                np.testing.assert_allclose(n, p.numpy(), rtol=RTOL, atol=ATOL)
+
+            out = tensor.atleast_3d()
+            out_ref = np.atleast_3d(input)
+
+            for n, p in zip(out_ref, out):
+                np.testing.assert_allclose(n, p.numpy(), rtol=RTOL, atol=ATOL)
+
+
 if __name__ == '__main__':
     unittest.main()