Add tests for coin-or#815

Author: MBradbury

pulp/tests/test_pulp.py

@@ -7,6 +7,7 @@
 import re
 import tempfile
 import unittest
+from decimal import Decimal
 
 from pulp import (
     LpAffineExpression,
@@ -1792,6 +1793,70 @@ def test_regression_805(self):
             self.assertEqual(c.name, "Test2")
             self.assertEqual(c.expr.name, "Test1")
 
+        def test_decimal_815(self):
+            # See: https://github.com/coin-or/pulp/issues/815
+            m1 = 3
+            m2 = Decimal("8.1")
+            extra = 5
+
+            x = LpVariable("x", lowBound=0, upBound=50, cat=LpContinuous)
+            y = LpVariable("y", lowBound=0, upBound=Decimal("32.24"), cat=LpContinuous)
+            include_extra = LpVariable("include_extra1", cat=LpBinary)
+
+            prob = LpProblem("graph", LpMaximize)
+
+            prob += y
+
+            # y = 3x + 5 | y = 3x
+            e1 = x * m1 + include_extra * extra - y
+            c1 = e1 == 0
+            prob += c1
+
+            # y = 8.1x - 6
+            e2 = x * m2 - 6 - y
+            c2 = e2 == 0
+            prob += c2
+
+            # This generates two possible systems of equations,
+            # y = 3x + 5
+            # y = 8.1x - 6
+            # this intersects at ~(11/5, 58/5)
+
+            # OR
+            # y = 3x
+            # y = 8.1x-6
+            # this intersects at ~(6/5, 18/5)
+            pulpTestCheck(
+                prob,
+                self.solver,
+                [const.LpStatusOptimal],
+                {x: 2.15686, y: 11.4706},
+            )
+
+        def test_decimal_815_addinplace(self):
+            # See: https://github.com/coin-or/pulp/issues/815
+            m1 = 3
+            m2 = Decimal("8.1")
+            extra = 5
+
+            x = LpVariable("x", lowBound=0, upBound=50, cat=LpContinuous)
+            y = LpVariable("y", lowBound=0, upBound=Decimal("32.24"), cat=LpContinuous)
+            include_extra = LpVariable("include_extra1", cat=LpBinary)
+
+            expression = LpAffineExpression()
+            expression += x * m1 + include_extra*extra - y
+            self.assertEqual(str(expression), "5*include_extra1 + 3*x - y")
+
+            with self.assertRaises(TypeError):
+                second_expression = LpAffineExpression()
+                second_expression += x * m2 - 6 - y
+
+            second_expression = LpAffineExpression(constant=Decimal("0"))
+            second_expression += x * m2 - 6 - y
+            self.assertEqual(str(second_expression), "8.1*x - y - 6.0")
+
+            second_expression_2 = x * m2 - 6 - y
+            self.assertEqual(str(second_expression_2), "8.1*x - y - 6.0")
 
 class PULP_CBC_CMDTest(BaseSolverTest.PuLPTest):
     solveInst = PULP_CBC_CMD