diff --git a/Makefile b/Makefile
index ce2c184..3024816 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 .PHONY: test clean build test_deploy deploy
 
 test:
-	python -m pytest tests/*
+	pytest tests/*
 
 clean:
 	rm -rf build dist *.egg-info
diff --git a/README.md b/README.md
index f8c368e..965c3dd 100644
--- a/README.md
+++ b/README.md
@@ -39,7 +39,7 @@ pip install manga109api
 import manga109api
 from pprint import pprint
 
-# Instantiate a parser with the root directory of Manga109
+# (0) Instantiate a parser with the root directory of Manga109
 manga109_root_dir = "YOUR_DIR/Manga109_2017_09_28"
 p = manga109api.Parser(root_dir=manga109_root_dir)
 
diff --git a/manga109api/manga109api.py b/manga109api/manga109api.py
index b4f3fb9..922aad8 100644
--- a/manga109api/manga109api.py
+++ b/manga109api/manga109api.py
@@ -14,7 +14,7 @@ def __init__(self, root_dir):
         self.root_dir = pathlib.Path(root_dir)
         self.books = []  # book titles
 
-        with (self.root_dir / "books.txt").open("rt", encoding= 'utf-8') as f:
+        with (self.root_dir / "books.txt").open("rt", encoding='utf-8') as f:
             self.books = [line.rstrip() for line in f]
 
     def get_annotation(self, book):
@@ -82,6 +82,9 @@ def _format_annotation(annotation):
 def _format_page_dict_style(page):
     """
     Format page annotation data. Make page data have the same key, and align the style of dict.
+    For example,
+      in:  [{'body': [123], 'face': 123, 'frame': []}]
+      out: [{'body': [123], 'face': [123], 'frame': [], 'text': []}]
 
     Args:
         page (dict): Annotation data for all pages including info such as frame, text, etc.
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_func.py b/tests/test_func.py
new file mode 100644
index 0000000..3eb76e3
--- /dev/null
+++ b/tests/test_func.py
@@ -0,0 +1,49 @@
+import manga109api
+from pathlib import Path
+
+
+def test_img_path():
+    manga109_root_dir = "tests/data_dummy/"
+    p = manga109api.Parser(root_dir=manga109_root_dir)
+
+    img1 = Path(p.img_path(book="TitleA", index=0)).absolute()
+    img2 = Path("tests/data_dummy/images/TitleA/000.jpg").absolute()
+    assert(img1 == img2)
+
+
+def test_format_annotation():
+    annotation = {
+        'book': {
+            '@title': 'AAA',
+            'characters': {'character': [
+                {'id': '123', 'name': 'yyy'}
+            ]},
+            'pages': {'page': [
+                {'index': 234, 'width': 345, 'height': 456,
+                 'frame': [{'id': '567', 'xmin': 11, 'ymin': 22, 'xmax': 33, 'ymax': 44}]}
+            ]}
+        }
+    }
+    gt = {
+        'title': 'AAA',
+        'character': [{'id': '123', 'name': 'yyy'}],
+        'page': [
+            {'index': 234, 'width': 345, 'height': 456, 'face': [], 'body': [], 'text': [],
+             'frame': [{'id': '567', 'xmin': 11, 'ymin': 22, 'xmax': 33, 'ymax': 44}]}
+        ]
+    }
+
+    ret = manga109api.manga109api._format_annotation(annotation)
+    assert(gt == ret)
+
+def test_format_page_dict_style():
+    page = [{'body': [123], 'face': 123, 'frame': []}]
+    gt = [{'body': [123], 'face': [123], 'frame': [], 'text': []}]
+    manga109api.manga109api._format_page_dict_style(page)
+    assert(gt == page)
+
+def test_convert_str_to_int_recursively():
+    annotation = [{'@xmax': '234', 'id': '0007a8be'}]
+    gt = [{'@xmax': 234, 'id': '0007a8be'}]
+    manga109api.manga109api._convert_str_to_int_recursively(annotation)
+    assert(gt == annotation)