Move get_test_value method to the Variable (sub)classes

theano/compile/sharedvalue.py

@@ -150,6 +150,9 @@ class SharedVariable(Variable):
         else:
             self.container.value = copy.deepcopy(new_value)
 
+    def get_test_value(self):
+        return self.get_value(borrow=True, return_internal_type=True)
+
     def zero(self, borrow=False):
         """
         Set the values of a shared variable to 0.

theano/gof/__init__.py

@@ -58,7 +58,14 @@ from theano.gof.link import (
     WrapLinkerMany,
 )
 
-from theano.gof.op import Op, OpenMPOp, PureOp, COp, ops_with_inner_function
+from theano.gof.op import (
+    Op,
+    OpenMPOp,
+    PureOp,
+    COp,
+    ops_with_inner_function,
+    get_test_value,
+)
 
 from theano.gof.type import EnumType, EnumList, CEnumType
 

theano/gof/graph.py

@@ -383,19 +383,39 @@ class Variable(Node):
         self.tag = utils.ValidatingScratchpad("test_value", type.filter)
 
         self.type = type
+
         if owner is not None and not isinstance(owner, Apply):
             raise TypeError("owner must be an Apply instance", owner)
         self.owner = owner
+
         if index is not None and not isinstance(index, integer_types):
             raise TypeError("index must be an int", index)
         self.index = index
+
         if name is not None and not isinstance(name, string_types):
             raise TypeError("name must be a string", name)
         self.name = name
+
         self.auto_name = "auto_" + str(next(self.__count__))
 
         Variable.notify_construction_observers(self)
 
+    def get_test_value(self):
+        """Get the test value.
+
+        Raises
+        ------
+        AttributeError
+
+        """
+        if not hasattr(self.tag, "test_value"):
+            detailed_err_msg = utils.get_variable_trace_string(self)
+            raise AttributeError(
+                "{} has no test value {}".format(self, detailed_err_msg)
+            )
+
+        return self.tag.test_value
+
     def __str__(self):
         """Return a str representation of the Variable."""
         if self.name is not None:
@@ -583,6 +603,9 @@ class Constant(Variable):
         self.data = type.filter(data)
         utils.add_tag_trace(self)
 
+    def get_test_value(self):
+        return self.data
+
     def equals(self, other):
         # this does what __eq__ should do, but Variable and Apply should always be hashable by id
         return isinstance(other, Constant) and self.signature() == other.signature()

theano/scan_module/scan.py

@@ -523,7 +523,7 @@ def scan(
                 # Try to transfer test_value to the new variable
                 if config.compute_test_value != "off":
                     try:
-                        nw_slice.tag.test_value = gof.Op._get_test_value(_seq_val_slice)
+                        nw_slice.tag.test_value = gof.get_test_value(_seq_val_slice)
                     except AttributeError as e:
                         if config.compute_test_value != "ignore":
                             # No need to print a warning or raise an error now,
@@ -655,7 +655,7 @@ def scan(
             # Try to transfer test_value to the new variable
             if config.compute_test_value != "off":
                 try:
-                    arg.tag.test_value = gof.Op._get_test_value(actual_arg)
+                    arg.tag.test_value = gof.get_test_value(actual_arg)
                 except AttributeError as e:
                     if config.compute_test_value != "ignore":
                         # No need to print a warning or raise an error now,
@@ -716,7 +716,7 @@ def scan(
                 # Try to transfer test_value to the new variable
                 if config.compute_test_value != "off":
                     try:
-                        nw_slice.tag.test_value = gof.Op._get_test_value(
+                        nw_slice.tag.test_value = gof.get_test_value(
                             _init_out_var_slice
                         )
                     except AttributeError as e: