add support for fits: write test FITS file in setUp

tests/test_fits.py

@@ -45,4 +45,5 @@ class TestFitsHeaderOps(unittest.TestCase):
 
     def test_fits_getdata(self):
         data = fits.getdata(test_fits_file, ext=0)
-        self.assertEqual(data, None)
+        self.assertIsInstance(data, np.ndarray)
+        self.assertEqual(data.shape, (5, 5))