delete variable x in test

Author: quantresearch1

pyomo/contrib/solver/tests/solvers/test_solvers.py

@@ -1167,6 +1167,11 @@ def test_mutable_quadratic_objective_qp(
         self.assertAlmostEqual(m.x2.value, 1, places=4)
         self.assertAlmostEqual(results.incumbent_objective, 2, 4)
 
+        del m.x1
+        results = opt.solve(m)
+        self.assertAlmostEqual(m.x2.value, 1, places=4)
+        self.assertAlmostEqual(results.incumbent_objective, 1, 4)
+
     @parameterized.expand(input=_load_tests(all_solvers))
     def test_fixed_vars(
         self, name: str, opt_class: Type[SolverBase], use_presolve: bool