Refactor the usage of custom devices

tests/custom_devices.py

@@ -0,0 +1,13 @@
+"""A collection of Custom Devices"""
+
+import pennylane as qml
+
+
+class BaseCustomDeviceReturnsZero(qml.devices.Device):
+    def execute(self, circuits, execution_config=None):
+        return 0
+
+
+class BaseCustomDeviceReturnsTuple(qml.devices.Device):
+    def execute(self, circuits, execution_config=None):
+        return (0,)

tests/devices/modifiers/test_all_modifiers.py

@@ -52,6 +52,11 @@ def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig)
     assert dev.tracker.history["shots"] == [50]
 
 
+class BaseDummyDev(qml.devices.Device):
+    def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
+        return 0.0
+
+
 @pytest.mark.parametrize("modifier", (simulator_tracking, single_tape_support))
 class TestModifierDefaultBeahviour:
     """Test generic behavior for device modifiers."""
@@ -66,29 +71,23 @@ def test_adds_to_applied_modifiers_private_property(self, modifier):
         """Test that the modifier is added to the `_applied_modifiers` property."""
 
         @modifier
-        class DummyDev(qml.devices.Device):
-            def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-                return 0.0
+        class DummyDev(BaseDummyDev):
+            pass
 
         assert DummyDev._applied_modifiers == [modifier]
 
         @modifier
-        class DummyDev2(qml.devices.Device):
-
+        class DummyDev2(BaseDummyDev):
             _applied_modifiers = [None]  # some existing value
 
-            def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-                return 0.0
-
         assert DummyDev2._applied_modifiers == [None, modifier]
 
     def test_leaves_undefined_methods_untouched(self, modifier):
         """Test that undefined methods are left the same as the Device class methods."""
 
         @modifier
-        class DummyDev(qml.devices.Device):
-            def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-                return 0.0
+        class DummyDev(BaseDummyDev):
+            pass
 
         assert DummyDev.compute_derivatives == Device.compute_derivatives
         assert DummyDev.execute_and_compute_derivatives == Device.execute_and_compute_derivatives

tests/devices/modifiers/test_simulator_tracking.py

@@ -52,14 +52,16 @@ def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig)
     assert dev.tracker.history["shots"] == [100]
 
 
+class BaseDummyDev(qml.devices.Device):
+    def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
+        return 0.0
+
+
 def test_tracking_compute_derivatives():
     """Test the compute_derivatives tracking behavior."""
 
     @simulator_tracking
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return 0.0
-
+    class DummyDev(BaseDummyDev):
         def compute_derivatives(
             self, circuits, execution_config=qml.devices.DefaultExecutionConfig
         ):
@@ -80,10 +82,7 @@ def test_tracking_execute_and_compute_derivatives():
     """Test tracking the execute_and_compute_derivatives method."""
 
     @simulator_tracking
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return 0.0
-
+    class DummyDev(BaseDummyDev):
         def execute_and_compute_derivatives(
             self, circuits, execution_config=qml.devices.DefaultExecutionConfig
         ):
@@ -108,10 +107,7 @@ def test_tracking_compute_jvp():
     """Test the compute_jvp tracking behavior."""
 
     @simulator_tracking
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return 0.0
-
+    class DummyDev(BaseDummyDev):
         def compute_jvp(
             self, circuits, tangents, execution_config=qml.devices.DefaultExecutionConfig
         ):
@@ -132,10 +128,7 @@ def test_tracking_execute_and_compute_jvp():
     """Test tracking the execute_and_compute_jvp method."""
 
     @simulator_tracking
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return 0.0
-
+    class DummyDev(BaseDummyDev):
         def execute_and_compute_jvp(
             self, circuits, tangents, execution_config=qml.devices.DefaultExecutionConfig
         ):
@@ -161,10 +154,7 @@ def test_tracking_compute_vjp():
     """Test the compute_vjp tracking behavior."""
 
     @simulator_tracking
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return 0.0
-
+    class DummyDev(BaseDummyDev):
         def compute_vjp(
             self, circuits, cotangents, execution_config=qml.devices.DefaultExecutionConfig
         ):
@@ -185,10 +175,7 @@ def test_tracking_execute_and_compute_vjp():
     """Test tracking the execute_and_compute_derivatives method."""
 
     @simulator_tracking
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return 0.0
-
+    class DummyDev(BaseDummyDev):
         def execute_and_compute_vjp(
             self, circuits, cotangents, execution_config=qml.devices.DefaultExecutionConfig
         ):

tests/devices/modifiers/test_single_tape_support.py

@@ -20,13 +20,17 @@
 from pennylane.devices.modifiers import single_tape_support
 
 
+class BaseDummyDev(qml.devices.Device):
+    def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
+        return tuple(0.0 for _ in circuits)
+
+
 def test_wraps_execute():
     """Test that execute now accepts a single circuit."""
 
     @single_tape_support
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return tuple(0.0 for _ in circuits)
+    class DummyDev(BaseDummyDev):
+        pass
 
     t = qml.tape.QuantumScript()
     dev = DummyDev()
@@ -37,10 +41,7 @@ def test_wraps_compute_derivatives():
     """Test that compute_derivatives now accepts a single circuit."""
 
     @single_tape_support
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return tuple(0.0 for _ in circuits)
-
+    class DummyDev(BaseDummyDev):
         def compute_derivatives(
             self, circuits, execution_config=qml.devices.DefaultExecutionConfig
         ):
@@ -55,10 +56,7 @@ def test_wraps_execute_and_compute_derivatives():
     """Test that execute_and_compute_derivatives now accepts a single circuit."""
 
     @single_tape_support
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return tuple(0.0 for _ in circuits)
-
+    class DummyDev(BaseDummyDev):
         def execute_and_compute_derivatives(
             self, circuits, execution_config=qml.devices.DefaultExecutionConfig
         ):
@@ -74,10 +72,7 @@ def test_wraps_compute_jvp():
     """Test that compute_jvp now accepts a single circuit."""
 
     @single_tape_support
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return tuple(0.0 for _ in circuits)
-
+    class DummyDev(BaseDummyDev):
         def compute_jvp(
             self, circuits, tangents, execution_config=qml.devices.DefaultExecutionConfig
         ):
@@ -94,10 +89,7 @@ def test_wraps_execute_and_compute_jvp():
     """Test that execute_and_compute_jvp now accepts a single circuit."""
 
     @single_tape_support
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return tuple(0.0 for _ in circuits)
-
+    class DummyDev(BaseDummyDev):
         def execute_and_compute_jvp(
             self, circuits, tangents, execution_config=qml.devices.DefaultExecutionConfig
         ):
@@ -114,10 +106,7 @@ def test_wraps_compute_vjp():
     """Test that compute_vjp now accepts a single circuit."""
 
     @single_tape_support
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return tuple(0.0 for _ in circuits)
-
+    class DummyDev(BaseDummyDev):
         def compute_vjp(
             self, circuits, cotangents, execution_config=qml.devices.DefaultExecutionConfig
         ):
@@ -134,10 +123,7 @@ def test_wraps_execute_and_compute_vjp():
     """Test that execute_and_compute_vjp now accepts a single circuit."""
 
     @single_tape_support
-    class DummyDev(qml.devices.Device):
-        def execute(self, circuits, execution_config=qml.devices.DefaultExecutionConfig):
-            return tuple(0.0 for _ in circuits)
-
+    class DummyDev(BaseDummyDev):
         def execute_and_compute_vjp(
             self, circuits, cotangents, execution_config=qml.devices.DefaultExecutionConfig
         ):