[#161] Add a test for xgboost classifier support

This test is currently failing if you have xgboost installed. If you don't have
xgboost installed, it skips itself to prevent failures due to missing packages
and dependencies.

hlink/tests/core/classifier_test.py

@@ -0,0 +1,23 @@
+import pytest
+
+from hlink.linking.core.classifier import choose_classifier
+
+try:
+    import xgboost
+except ModuleNotFoundError:
+    xgboost_available = False
+else:
+    xgboost_available = True
+
+@pytest.mark.skipif(not xgboost_available, reason="requires the xgboost library")
+def test_choose_classifier_supports_xgboost():
+    """
+    If the xgboost module is installed, then choose_classifier() supports a model
+    type of "xgboost".
+    """
+    params = {
+        "max_depth": 2,
+        "eta": 0.5,
+    }
+    classifier = choose_classifier("xgboost", params, "match")
+    assert classifier.getLabelCol() == "match"