Add a real test for pre_greedy_local_optimizer

tests/gof/test_opt.py

@@ -587,9 +587,44 @@ def test_pre_constant_merge():
 
 
 def test_pre_greedy_local_optimizer():
+
     empty_fgraph = FunctionGraph([], [])
+
+    x = MyVariable("x")
+    y = MyVariable("y")
+    c1 = Constant(MyType(), 1, "c1")
+    c2 = Constant(MyType(), 2, "c2")
+    o1 = op2(c1, c2)
+    o3 = op1(c1, y)
+    o2 = op1(o1, c2, x, o3, o1)
+
+    assert o2.owner.inputs[0].owner is not None
+    assert o2.owner.inputs[4].owner is not None
+
+    # This should fold `o1`, because it has only `Constant` arguments, and
+    # replace it with the `Constant` result
+    cst = pre_greedy_local_optimizer(empty_fgraph, [constant_folding], o2)
+
+    assert cst.owner.inputs[0].owner is None
+    assert cst.owner.inputs[1] is c2
+    assert cst.owner.inputs[2] is x
+    assert cst.owner.inputs[3] is o3
+    assert cst.owner.inputs[4] is cst.owner.inputs[0]
+
+    # We're going to do it again, except this time `o1` is
+    # in the `fgraph`, so it shouldn't be folded
+    fg = FunctionGraph([], [o1], clone=False)
+    o2 = op1(o1, c2, x, o3, o1)
+
+    cst = pre_greedy_local_optimizer(fg, [constant_folding], o2)
+
+    assert cst.owner.inputs[0] is o1
+    assert cst.owner.inputs[4] is cst.owner.inputs[0]
+
+    # What exactly is this supposed to test?
     ms = MakeSlice()(1)
     cst = pre_greedy_local_optimizer(empty_fgraph, [constant_folding], ms)
+
     assert isinstance(cst, SliceConstant)
 
     # Make sure constant of slice signature is hashable.