Add real tests for pre_constant_merge

tests/gof/test_opt.py

@@ -542,16 +542,55 @@ class TestEquilibrium:
         assert str(g) == "FunctionGraph(Op1(x, y))"
 
 
-def test_pre_constant_merge_slice():
+def test_pre_constant_merge():
+
+    empty_fgraph = FunctionGraph([], [])
+
+    x = MyVariable("x")
+    y = MyVariable("y")
+    c1 = Constant(MyType(), 1, "c1")
+    c2 = Constant(MyType(), 1, "c1")
+    o1 = op2(c1, x)
+    o2 = op1(o1, y, c2)
+
+    assert c1 is not c2
+
+    res = pre_constant_merge(empty_fgraph, [o2])
+
+    assert [o2] == res
+    assert o2.owner.inputs[2] is c1
+
+    o2 = op1(o1, y, c2)
+    fg = FunctionGraph([x, y], [o2], clone=False)
+
+    assert o2.owner in fg.apply_nodes
+
+    res = pre_constant_merge(fg, [o2])
+
+    assert res == [o2]
+    assert o2.owner.inputs[2] is c2
+
+    # What is this supposed to test?
     ms = MakeSlice()(1)
-    pre_constant_merge([ms])
+    res = pre_constant_merge(empty_fgraph, [ms])
+
+    assert res == [ms]
+
     const_slice = SliceConstant(type=slicetype, data=slice(1, None, 2))
+
+    assert isinstance(const_slice, Constant)
+
     adv = AdvancedSubtensor()(tt.matrix(), [2, 3], const_slice)
-    pre_constant_merge(adv)
 
-    fgraph = FunctionGraph([], [])
-    cst = pre_greedy_local_optimizer(fgraph, [constant_folding], ms)
+    res = pre_constant_merge(empty_fgraph, adv)
+    assert res == [adv]
+
+
+def test_pre_greedy_local_optimizer():
+    empty_fgraph = FunctionGraph([], [])
+    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.
-    hash(cst.signature())
+    assert isinstance(hash(cst.signature()), int)