add unit test

Signed-off-by: chenglu <[email protected]>

econml/dowhy.py

@@ -233,11 +233,14 @@ def __getattr__(self, attr):
             raise AttributeError(attr)
         elif attr == "dowhy_":
             if "dowhy_" not in dir(self):
-                raise RuntimeError("Please call DoWhyWrapper.fit first before any other operations")
+                raise AttributeError("Please call `DoWhyWrapper.fit` first before any other operations.")
             else:
                 return self.dowhy_
         elif attr in ['_cate_estimator', 'identified_estimand_', 'estimate_']:
-            return getattr(self, attr)
+            if attr in dir(self):
+                return getattr(self, attr)
+            else:
+                raise AttributeError(f"call `DoWhyWrapper.fit` first before any other operations.")
         elif attr.startswith('dowhy__'):
             return getattr(self.dowhy_, attr[len('dowhy__'):])
         elif hasattr(self.estimate_._estimator_object, attr):

econml/tests/test_dowhy.py

@@ -95,3 +95,12 @@ def test_store_dataframe_name(self):
         np.testing.assert_array_equal(est._effect_modifiers, X_name)
         np.testing.assert_array_equal(est._treatment, [T_name])
         np.testing.assert_array_equal(est._outcome, [Y_name])
+
+    def test_dowhy_without_fit(self):
+        with self.assertRaises(AttributeError) as context:
+            LinearDRLearner().dowhy.refute_estimate(method_name="random_common_cause", num_simulations=3)
+        self.assertTrue("Please call `DoWhyWrapper.fit` first before any other operations." in str(context.exception))
+
+        with self.assertRaises(AttributeError) as context:
+            LinearDRLearner().dowhy._estimator_object
+        self.assertTrue("call `DoWhyWrapper.fit` first before any other operations." in str(context.exception))