added unit test

README.md

@@ -30,7 +30,7 @@ A simple example on how to use this package:
 
 ```python
 import numpy as np
-from csst_proto import flip_image, print_data
+from csst_proto.top_level_interface import flip_image, read_test_image
 from astropy.io import fits
 
 # read an L0 image

csst_proto/flip_image.py

@@ -30,4 +30,4 @@ def flip_image(img: np.ndarray):
 def read_test_image():
     """ read test image """
     fp_img = PACKAGE_PATH + "/data/test_image.txt"
-    return np.loadtxt(fp_img)
+    return np.loadtxt(fp_img, dtype=int)