Add basic test for the Regression model (#618)

tests/test_regression.py

@@ -0,0 +1,14 @@
+# -*- coding: utf-8 -*-
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+from bugbug.models.regression import RegressionModel
+
+
+def test_get_regression_labels():
+    model = RegressionModel()
+    classes, _ = model.get_labels()
+    assert classes[447581] == 0
+    assert classes[518272] == 1