Add test for format command

tests/test_format.py

+# -*- coding: utf-8 -*-
+
+from pathlib import Path
+
+import pytest
+
+from dan.datasets.format.atr import ATRDatasetFormatter, remove_spaces
+
+
+@pytest.mark.parametrize(
+    "text,trimmed",
+    (
+        ("no_spaces", "no_spaces"),
+        (" beginning", "beginning"),
+        ("ending ", "ending"),
+        (" both ", "both"),
+        ("    consecutive", "consecutive"),
+        ("\ttab", "tab"),
+    ),
+)
+def test_remove_spaces(text, trimmed):
+    assert remove_spaces(text) == trimmed
+
+
+@pytest.mark.parametrize(
+    "image_format, expected_format",
+    (
+        (".png", "png"),
+        ("png", "png"),
+    ),
+)
+def test_image_format_parsing(image_format, expected_format):
+    formatter = ATRDatasetFormatter(
+        dataset=Path("my_dataset"), image_format=image_format, remove_spaces=True
+    )
+    assert formatter.image_format == expected_format