Test poi.In for ipopt solver

Author: metab0t

tests/test_in_constraint.py

@@ -0,0 +1,24 @@
+import pyoptinterface as poi
+
+import pytest
+
+
+def test_in_constraint_sense(ipopt_model_ctor):
+    model = ipopt_model_ctor()
+
+    x = model.add_variable(lb=0.0)
+    y = model.add_variable(lb=0.0)
+
+    expr = x + y
+    model.add_linear_constraint(expr, poi.In, 0.0, 1.0)
+    model.set_objective(expr)
+    model.optimize()
+
+    expr_value = model.get_value(expr)
+    assert expr_value == pytest.approx(0.0, abs=1e-6)
+
+    model.set_objective(-expr)
+    model.optimize()
+
+    expr_value = model.get_value(expr)
+    assert expr_value == pytest.approx(1.0, rel=1e-6)