diff --git a/labelme/__init__.py b/labelme/__init__.py
index ad38eaac622178c0d48aad9ec471351da19d6a6c..84b71d3b4fe09b9b86eff82dff199edd4edadc32 100644
--- a/labelme/__init__.py
+++ b/labelme/__init__.py
@@ -1,3 +1,4 @@
 # flake8: noqa
 
+from labelme import testing
 from labelme import utils
diff --git a/labelme/testing.py b/labelme/testing.py
new file mode 100644
index 0000000000000000000000000000000000000000..587298ec75f36b7077242d02e0758e6692a601e6
--- /dev/null
+++ b/labelme/testing.py
@@ -0,0 +1,25 @@
+import json
+import os.path as osp
+
+import labelme.utils
+
+
+def assert_labelfile_sanity(filename):
+    assert osp.exists(filename)
+
+    data = json.load(open(filename))
+
+    assert 'imagePath' in data
+    imageData = data.get('imageData', None)
+    if imageData is None:
+        assert osp.exists(data['imagePath'])
+    img = labelme.utils.img_b64_to_arr(imageData)
+
+    H, W = img.shape[:2]
+    assert 'shapes' in data
+    for shape in data['shapes']:
+        assert 'label' in shape
+        assert 'points' in shape
+        for x, y in shape['points']:
+            assert 0 <= x <= W
+            assert 0 <= y <= H
diff --git a/tests/test_app.py b/tests/test_app.py
new file mode 100644
index 0000000000000000000000000000000000000000..42a8c4cc7a1c7e3a1eb97dcafea129d86be4090b
--- /dev/null
+++ b/tests/test_app.py
@@ -0,0 +1,58 @@
+import os.path as osp
+import shutil
+import tempfile
+
+import labelme.app
+import labelme.testing
+
+
+here = osp.dirname(osp.abspath(__file__))
+data_dir = osp.join(here, 'data')
+
+
+def test_MainWindow_open(qtbot):
+    win = labelme.app.MainWindow()
+    qtbot.addWidget(win)
+    win.show()
+    win.close()
+
+
+def test_MainWindow_open_json(qtbot):
+    filename = osp.join(data_dir, 'apc2016_obj3.json')
+    labelme.testing.assert_labelfile_sanity(filename)
+    win = labelme.app.MainWindow(filename=filename)
+    qtbot.addWidget(win)
+    win.show()
+    win.close()
+
+
+def test_MainWindow_annotate_jpg(qtbot):
+    tmp_dir = tempfile.mkdtemp()
+    filename = osp.join(tmp_dir, 'apc2016_obj3.jpg')
+    shutil.copy(osp.join(data_dir, 'apc2016_obj3.jpg'),
+                filename)
+    output = osp.join(tmp_dir, 'apc2016_obj3.json')
+
+    win = labelme.app.MainWindow(filename=filename, output=output)
+    qtbot.addWidget(win)
+    win.show()
+
+    def check_imageData():
+        assert hasattr(win, 'imageData')
+        assert win.imageData is not None
+
+    qtbot.waitUntil(check_imageData)  # wait for loadFile
+
+    label = 'shelf'
+    points = [
+        (26, 70),
+        (176, 730),
+        (986, 742),
+        (1184, 102),
+    ]
+    shape = label, points, None, None
+    shapes = [shape]
+    win.loadLabels(shapes)
+    win.saveFile()
+
+    labelme.testing.assert_labelfile_sanity(output)
diff --git a/tests/test_labelDialog.py b/tests/test_labelDialog.py
index 068acdb0492c5f0a93df5508f0a841a46cebe14e..15648e1f6d3d79b236413628d9b892059bd6c9e9 100644
--- a/tests/test_labelDialog.py
+++ b/tests/test_labelDialog.py
@@ -57,9 +57,9 @@ def test_LabelDialog_popUp(qtbot):
     # popUp(text='cat')
 
     def interact():
-        qtbot.keyClick(widget.edit, QtCore.Qt.Key_P)  # enter 'p' for 'person'
-        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)
-        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)
+        qtbot.keyClick(widget.edit, QtCore.Qt.Key_P)  # enter 'p' for 'person'  # NOQA
+        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)  # NOQA
+        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)  # NOQA
 
     QtCore.QTimer.singleShot(500, interact)
     text = widget.popUp('cat')
@@ -68,8 +68,8 @@ def test_LabelDialog_popUp(qtbot):
     # popUp()
 
     def interact():
-        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)
-        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)
+        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)  # NOQA
+        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)  # NOQA
 
     QtCore.QTimer.singleShot(500, interact)
     text = widget.popUp()
@@ -78,9 +78,9 @@ def test_LabelDialog_popUp(qtbot):
     # popUp() + key_Up
 
     def interact():
-        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Up)  # 'person' -> 'dog'
-        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)
-        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)
+        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Up)  # 'person' -> 'dog'  # NOQA
+        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)  # NOQA
+        qtbot.keyClick(widget.edit, QtCore.Qt.Key_Enter)  # NOQA
 
     QtCore.QTimer.singleShot(500, interact)
     text = widget.popUp()