Refactor imports and test design in tests.gof.test_op

tests/gof/test_op.py

 import numpy as np
 import pytest
-
 import theano
 import theano.gof.op as op
+import theano.tensor as tt
+
 from six import string_types
-from theano.gof.type import Type, Generic
+from theano import scalar, shared
+from theano.configparser import change_flags
 from theano.gof.graph import Apply, Variable
-import theano.tensor as T
-from theano import scalar
-from theano import shared
+from theano.gof.type import Generic, Type
 
 config = theano.config
 Op = op.Op
@@ -238,15 +238,15 @@ class TestMakeThunk:
 
             __props__ = ()
 
-            itypes = [T.dmatrix]
-            otypes = [T.dmatrix]
+            itypes = [tt.dmatrix]
+            otypes = [tt.dmatrix]
 
             def perform(self, node, inputs, outputs):
                 inp = inputs[0]
                 output = outputs[0]
                 output[0] = inp * 2
 
-        x_input = T.dmatrix("x_input")
+        x_input = tt.dmatrix("x_input")
         f = theano.function([x_input], DoubleOp()(x_input))
         inp = np.random.rand(5, 4)
         out = f(inp)
@@ -255,17 +255,17 @@ class TestMakeThunk:
 
 def test_test_value_python_objects():
     for x in ([0, 1, 2], 0, 0.5, 1):
-        assert (op.get_test_value(x) == x).all()
+        assert np.all(op.get_test_value(x) == x)
 
 
 def test_test_value_ndarray():
     x = np.zeros((5, 5))
     v = op.get_test_value(x)
-    assert (v == x).all()
+    assert np.all(v == x)
 
 
 def test_test_value_constant():
-    x = T.as_tensor_variable(np.zeros((5, 5)))
+    x = tt.as_tensor_variable(np.zeros((5, 5)))
     v = op.get_test_value(x)
 
     assert np.all(v == np.zeros((5, 5)))
@@ -278,62 +278,37 @@ def test_test_value_shared():
     assert np.all(v == np.zeros((5, 5)))
 
 
+@change_flags(compute_test_value="raise")
 def test_test_value_op():
-    try:
-        prev_value = config.compute_test_value
-        config.compute_test_value = "raise"
-        x = T.log(np.ones((5, 5)))
-        v = op.get_test_value(x)
-
-        assert np.allclose(v, np.zeros((5, 5)))
-    finally:
-        config.compute_test_value = prev_value
 
+    x = tt.log(np.ones((5, 5)))
+    v = op.get_test_value(x)
 
-def test_get_debug_values_no_debugger():
-    "get_debug_values should return [] when debugger is off"
-
-    prev_value = config.compute_test_value
-    try:
-        config.compute_test_value = "off"
+    assert np.allclose(v, np.zeros((5, 5)))
 
-        x = T.vector()
 
-        for x_val in op.get_debug_values(x):
-            assert False
+@change_flags(compute_test_value="off")
+def test_get_debug_values_no_debugger():
+    """Tests that `get_debug_values` returns `[]` when debugger is off."""
 
-    finally:
-        config.compute_test_value = prev_value
+    x = tt.vector()
+    assert op.get_debug_values(x) == []
 
 
+@change_flags(compute_test_value="ignore")
 def test_get_det_debug_values_ignore():
-    # get_debug_values should return [] when debugger is ignore
-    # and some values are missing
-
-    prev_value = config.compute_test_value
-    try:
-        config.compute_test_value = "ignore"
-
-        x = T.vector()
+    """Tests that `get_debug_values` returns `[]` when debugger is set to "ignore" and some values are missing."""
 
-        for x_val in op.get_debug_values(x):
-            assert False
-
-    finally:
-        config.compute_test_value = prev_value
+    x = tt.vector()
+    assert op.get_debug_values(x) == []
 
 
 def test_get_debug_values_success():
-    # tests that get_debug_value returns values when available
-    # (and the debugger is on)
+    """Tests that `get_debug_value` returns values when available (and the debugger is on)."""
 
-    prev_value = config.compute_test_value
     for mode in ["ignore", "warn", "raise"]:
-
-        try:
-            config.compute_test_value = mode
-
-            x = T.vector()
+        with change_flags(compute_test_value=mode):
+            x = tt.vector()
             x.tag.test_value = np.zeros((4,), dtype=config.floatX)
             y = np.zeros((5, 5))
 
@@ -348,33 +323,11 @@ def test_get_debug_values_success():
 
             assert iters == 1
 
-        finally:
-            config.compute_test_value = prev_value
-
 
+@change_flags(compute_test_value="raise")
 def test_get_debug_values_exc():
-    # tests that get_debug_value raises an exception when
-    # debugger is set to raise and a value is missing
-
-    prev_value = config.compute_test_value
-    try:
-        config.compute_test_value = "raise"
+    """Tests that `get_debug_value` raises an exception when debugger is set to raise and a value is missing."""
 
-        x = T.vector()
-
-        try:
-            for x_val in op.get_debug_values(x):
-                # this assert catches the case where we
-                # erroneously get a value returned
-                assert False
-            raised = False
-        except AttributeError:
-            raised = True
-
-        # this assert catches the case where we got []
-        # returned, and possibly issued a warning,
-        # rather than raising an exception
-        assert raised
-
-    finally:
-        config.compute_test_value = prev_value
+    with pytest.raises(AttributeError):
+        x = tt.vector()
+        assert op.get_debug_values(x) == []