fix UT in download (#149)

Co-authored-by: Sikai Yao <yaosk@dp.tech>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

tests/utils/test_dl_dpgen2_arti_by_def.py

@@ -42,6 +42,9 @@ class MockedStep:
     inputs = MockedDef()
     outputs = MockedDef()
 
+    def __init__(self, key) -> None:
+        self.key = key
+
     def __getitem__(
         self,
         kk,
@@ -58,9 +61,13 @@ class Mockedwf:
 
     def query_step_by_key(self, key):
         if key == sorted(self.keys):
-            return [MockedStep(), MockedStep(), MockedStep()]
+            return [
+                MockedStep(self.keys[0]),
+                MockedStep(self.keys[1]),
+                MockedStep(self.keys[2]),
+            ]
         else:
-            return [MockedStep() for kk in key]
+            return [MockedStep(kk) for kk in key]
 
     def query_keys_of_steps(self):
         return self.keys