Add tests for division and normalization in ProdExpr

Introduces tests for division operations and normalization behavior in ProdExpr, including checks for division by constants, variables, and self, as well as normalization to ConstExpr, PolynomialExpr, and SinExpr. Enhances test coverage for expression handling in the symbolic math module.

Author: Zeroto521

tests/test_ProdExpr.py

@@ -1,7 +1,7 @@
 import pytest
 
-from pyscipopt import Expr, Model, exp, log, sin, sqrt
-from pyscipopt.scip import PolynomialExpr, PowExpr, ProdExpr, Term
+from pyscipopt import Expr, Model, exp, sin, sqrt
+from pyscipopt.scip import ConstExpr, PolynomialExpr, PowExpr, ProdExpr, SinExpr, Term
 
 
 @pytest.fixture(scope="module")
@@ -71,6 +71,20 @@ def test_mul(model):
     assert str(expr) == "PowExpr(ProdExpr({(Term(x), Term(y)): 3.0}), 2.0)"
 
 
+def test_div(model):
+    m, x, y = model
+
+    expr = 2 * (sin(x) * y)
+    assert (
+        str(expr / 0.5) == "ProdExpr({(SinExpr(Term(x)), Expr({Term(y): 1.0})): 4.0})"
+    )
+    assert (
+        str(expr / x)
+        == "ProdExpr({(ProdExpr({(SinExpr(Term(x)), Expr({Term(y): 1.0})): 2.0}), PowExpr(Expr({Term(x): 1.0}), -1.0)): 1.0})"
+    )
+    assert str(expr / expr) == "Expr({Term(): 1.0})"
+
+
 def test_cmp(model):
     m, x, y = model
 
@@ -81,3 +95,26 @@ def test_cmp(model):
         str(expr1 == 1)
         == "ExprCons(ProdExpr({(SinExpr(Term(x)), Expr({Term(y): 1.0})): 1.0}), 1.0, 1.0)"
     )
+
+
+def test_normalize(model):
+    m, x, y = model
+
+    expr = ProdExpr()._normalize()
+    assert isinstance(expr, ConstExpr)
+    assert str(expr) == "Expr({Term(): 0.0})"
+
+    expr = sin(x) * y
+    assert isinstance(expr, ProdExpr)
+    assert str(expr - expr) == "Expr({Term(): 0.0})"
+
+    expr = ProdExpr(Term(x))._normalize()
+    assert type(expr) is PolynomialExpr
+    assert str(expr) == "Expr({Term(x): 1.0})"
+
+    expr = ProdExpr(sin(x))._normalize()
+    assert isinstance(expr, SinExpr)
+    assert str(expr) == "SinExpr(Term(x))"
+
+    expr = sin(x) * y
+    assert str(expr._normalize()) == str(expr)