Fix validation split and add test

tests/test_validation.py

@@ -0,0 +1,17 @@
+from library.train_util import split_train_val
+
+
+def test_split_train_val():
+    paths = ["path1", "path2", "path3", "path4", "path5", "path6", "path7"]
+    sizes = [(1, 1), (2, 2), None, (4, 4), (5, 5), (6, 6), None]
+    result_paths, result_sizes = split_train_val(paths, sizes, True, 0.2, 1234)
+    assert result_paths == ["path2", "path3", "path6", "path5", "path1", "path4"], result_paths
+    assert result_sizes == [(2, 2), None, (6, 6), (5, 5), (1, 1), (4, 4)], result_sizes
+
+    result_paths, result_sizes = split_train_val(paths, sizes, False, 0.2, 1234)
+    assert result_paths == ["path7"], result_paths
+    assert result_sizes == [None], result_sizes
+
+
+if __name__ == "__main__":
+    test_split_train_val()