diff --git a/ods2md.py b/ods2md.py
index b7dc83f..18dd95f 100755
--- a/ods2md.py
+++ b/ods2md.py
@@ -45,7 +45,7 @@ def display_text(cell):
 def display_len(s):
     return sum(DISPLAY_WIDTH[unicodedata.east_asian_width(c)] for c in s)
 
-def main(odf_path):
+def main(odf_path, out_file):
     ods = ezodf.opendoc(odf_path)
 
     for sheet in ods.sheets:
@@ -53,7 +53,7 @@ def main(odf_path):
         if not any(column_widths):
             continue
 
-        print('##', sheet.name)
+        print('##', sheet.name, file=out_file)
         printed_header = False
 
         for row in sheet.rows():
@@ -61,22 +61,22 @@ def main(odf_path):
             if not any(contents):
                 continue
 
-            print('|', end='')
+            print('|', end='', file=out_file)
             for m, content in enumerate(contents):
                 column_width = column_widths[m]
                 if not column_width:
                     continue
                 disp_len = column_width + len(content) - display_len(content)
-                print(' {0:<{1}}'.format(content, disp_len), end=' |')
-            print()
+                print(' {0:<{1}}'.format(content, disp_len), end=' |', file=out_file)
+            print(file=out_file)
 
             if not printed_header:
                 printed_header = True
-                print('|', end='')
+                print('|', end='', file=out_file)
                 for w in column_widths:
                     if w:
-                        print(':', '-' * (w+1), '|', sep='', end='')
-                print()
+                        print(':', '-' * (w+1), '|', sep='', end='', file=out_file)
+                print(file=out_file)
 
 if __name__ == '__main__':
-    main(sys.argv[1])
+    main(sys.argv[1], sys.stdout)
diff --git a/test.py b/test.py
new file mode 100644
index 0000000..64c96dd
--- /dev/null
+++ b/test.py
@@ -0,0 +1,18 @@
+import ods2md
+
+import unittest
+import os.path
+import io
+
+class Test(unittest.TestCase):
+    def perform_test(self, base):
+        output = io.StringIO()
+        ods2md.main(os.path.join('test', base + '.ods'), output)
+        with open(os.path.join('test', base + '.md'), 'r') as f:
+            self.assertMultiLineEqual(f.read(), output.getvalue())
+
+    def test_sample(self):
+        self.perform_test('sample')
+
+    def test_padded(self):
+        self.perform_test('padded')
diff --git a/test/padded.md b/test/padded.md
new file mode 100644
index 0000000..30c1a26
--- /dev/null
+++ b/test/padded.md
@@ -0,0 +1,8 @@
+## Sheet1
+| X   | Y          |
+|:----|:-----------|
+| 0.1 | 1999-12-31 |
+| 0.2 | 2000-01-01 |
+|     | !          |
+| 0.4 |            |
+| 0.7 | ?          |
diff --git a/test/padded.ods b/test/padded.ods
new file mode 100644
index 0000000..d7e5c8f
Binary files /dev/null and b/test/padded.ods differ
diff --git a/test/sample.md b/test/sample.md
new file mode 100644
index 0000000..eea0fd9
--- /dev/null
+++ b/test/sample.md
@@ -0,0 +1,12 @@
+## Sheet1
+| 版本         | 英文代號         | 中譯               |
+|:-------------|:-----------------|:-------------------|
+| Ubuntu 17.04 | Zesty Zapus      | 熱情的北美草原跳鼠 |
+| Ubuntu 16.10 | Yakkety Yak      | 喋喋不休的氂牛     |
+| Ubuntu 16.04 | Xenial Xerus     | 好客的非洲地松鼠   |
+| Ubuntu 15.10 | Wily Werewolf    | 老謀深算的狼人     |
+| Ubuntu 15.04 | Vivid Vervet     | 活潑的長尾黑顎猴   |
+| Ubuntu 14.10 | Utopic Unicorn   | 烏托邦的獨角獸     |
+| Ubuntu 14.04 | Trusty Tahr      | 可靠的塔爾羊       |
+| Ubuntu 13.10 | Saucy Salamander | 活潑的蠑螈         |
+| Ubuntu 13.04 | Raring Ringtail  | 卯足了勁的環尾貓熊 |
diff --git a/test/sample.ods b/test/sample.ods
new file mode 100644
index 0000000..ee4dcd0
Binary files /dev/null and b/test/sample.ods differ