[ci] prevent Python tests from leaving behind files (#6626)

Co-authored-by: James Lamb <jaylamb20@gmail.com>

tests/python_package_test/test_dask.py

@@ -1527,11 +1527,11 @@ def test_predict_with_raw_score(task, output, cluster):
             assert_eq(raw_predictions, pred_proba_raw)
 
 
-def test_distributed_quantized_training(cluster):
+def test_distributed_quantized_training(tmp_path, cluster):
     with Client(cluster) as client:
         X, y, w, _, dX, dy, dw, _ = _create_data(objective="regression", output="array")
 
-        np.savetxt("data_dask.csv", np.hstack([np.array([y]).T, X]), fmt="%f,%f,%f,%f,%f")
+        np.savetxt(tmp_path / "data_dask.csv", np.hstack([np.array([y]).T, X]), fmt="%f,%f,%f,%f,%f")
 
         params = {
             "boosting_type": "gbdt",

tests/python_package_test/test_plotting.py

@@ -177,7 +177,7 @@ def test_plot_tree(breast_cancer_split):
 
 
 @pytest.mark.skipif(not GRAPHVIZ_INSTALLED, reason="graphviz is not installed")
-def test_create_tree_digraph(breast_cancer_split):
+def test_create_tree_digraph(tmp_path, breast_cancer_split):
     X_train, _, y_train, _ = breast_cancer_split
 
     constraints = [-1, 1] * int(X_train.shape[1] / 2)
@@ -193,6 +193,7 @@ def test_create_tree_digraph(breast_cancer_split):
         show_info=["split_gain", "internal_value", "internal_weight"],
         name="Tree4",
         node_attr={"color": "red"},
+        directory=tmp_path,
     )
     graph.render(view=False)
     assert isinstance(graph, graphviz.Digraph)
@@ -213,7 +214,7 @@ def test_create_tree_digraph(breast_cancer_split):
 
 
 @pytest.mark.skipif(not GRAPHVIZ_INSTALLED, reason="graphviz is not installed")
-def test_tree_with_categories_below_max_category_values():
+def test_tree_with_categories_below_max_category_values(tmp_path):
     X_train, y_train = _categorical_data(2, 10)
     params = {
         "n_estimators": 10,
@@ -238,6 +239,7 @@ def test_tree_with_categories_below_max_category_values():
         name="Tree4",
         node_attr={"color": "red"},
         max_category_values=10,
+        directory=tmp_path,
     )
     graph.render(view=False)
     assert isinstance(graph, graphviz.Digraph)
@@ -257,7 +259,7 @@ def test_tree_with_categories_below_max_category_values():
 
 
 @pytest.mark.skipif(not GRAPHVIZ_INSTALLED, reason="graphviz is not installed")
-def test_tree_with_categories_above_max_category_values():
+def test_tree_with_categories_above_max_category_values(tmp_path):
     X_train, y_train = _categorical_data(20, 30)
     params = {
         "n_estimators": 10,
@@ -282,6 +284,7 @@ def test_tree_with_categories_above_max_category_values():
         name="Tree4",
         node_attr={"color": "red"},
         max_category_values=4,
+        directory=tmp_path,
     )
     graph.render(view=False)
     assert isinstance(graph, graphviz.Digraph)