Make tests compatible with Python 3.7+

.github/workflows/test.yml

@@ -5,7 +5,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8]
+        python-version: [3.6, 3.7, 3.8, 3.9]
 
     steps:
     - name: Check out source code

Makefile

@@ -1,6 +1,6 @@
 PYTHON      := python3
 PYTEST      := pytest
-PIP         := pip3
+PIP         := $(PYTHON) -m pip
 PYTEST_ARGS := -W ignore::DeprecationWarning -vv -x --log-level=DEBUG
 VERSION     := 0.2
 
@@ -24,8 +24,11 @@ docs:
 docs-dev:
 	mkdocs build -d ../docs/dev/
 
-install:
+install-deps:
+	$(PIP) install -i https://pypi.gurobi.com gurobipy
 	$(PIP) install -r requirements.txt
+
+install:
 	$(PYTHON) setup.py install
 
 uninstall:

miplearn/solvers/tests/__init__.py

@@ -2,23 +2,29 @@
 #  Copyright (C) 2020, UChicago Argonne, LLC. All rights reserved.
 #  Released under the modified BSD license. See COPYING.md for more details.
 
+from inspect import isclass
 from miplearn import BasePyomoSolver, GurobiSolver, GurobiPyomoSolver
 from miplearn.problems.knapsack import KnapsackInstance, GurobiKnapsackInstance
 
 
 def _get_instance(solver):
-    if issubclass(solver, BasePyomoSolver) or isinstance(solver, BasePyomoSolver):
+    def _is_subclass_or_instance(solver, parentClass):
+        return isinstance(solver, parentClass) or (isclass(solver) and issubclass(solver, parentClass))
+
+    if _is_subclass_or_instance(solver, BasePyomoSolver):
         return KnapsackInstance(
             weights=[23., 26., 20., 18.],
             prices=[505., 352., 458., 220.],
             capacity=67.,
         )
-    if issubclass(solver, GurobiSolver) or isinstance(solver, GurobiSolver):
+
+    if _is_subclass_or_instance(solver, GurobiSolver):
         return GurobiKnapsackInstance(
             weights=[23., 26., 20., 18.],
             prices=[505., 352., 458., 220.],
             capacity=67.,
         )
+
     assert False