diff --git a/tests/test_dataset.py b/tests/test_dataset.py
index 3da2f3e0b9ced59d685ba8febf67bc09a514834c..d55e8d2c55ae1cc15a41c17aeae0581401bfa699 100644
--- a/tests/test_dataset.py
+++ b/tests/test_dataset.py
@@ -7,7 +7,8 @@ import icartt
 
 # working directory, example files
 wd = pathlib.Path(__file__).parent
-fns = (wd / "example_data").glob("*.ict")
+fns_pass = (wd / "example_data").glob("*.ict")
+fns_fail = (wd / "example_data" / "will_fail").glob("*.ict")
 
 
 def compareFiles(fn, strIn, strOut, skiplines=0, nlines=-1):  # pragma: no cover
@@ -310,42 +311,46 @@ class Create1001TestCase(unittest.TestCase):
 
 
 class BulkIOTestCase(unittest.TestCase):
+    # def testInvalid(self):
+    #     for fn in fns_fail:
+    #         with self.subTest(msg=f"Opening invalid file {str(fn)}"):
+    #             try:
+    #                 _ = icartt.Dataset(fn, loadData=True)
+    #             except: # TODO: failure tests could be more specific
+    #                 pass
+    #             else:
+    #                 self.fail('expected to fail')
+
     def testOpen(self):
-        for fn in fns:
+        for fn in fns_pass:
             with self.subTest(msg=f"Opening test file {str(fn)}"):
                 ict = icartt.Dataset(fn, loadData=False)
                 self.assertEqual(type(ict), icartt.Dataset)
 
     def testReadData(self):
-        for fn in fns:
+        for fn in fns_pass:
             with self.subTest(msg=f"Reading data from test file {str(fn)}"):
                 ict = icartt.Dataset(fn, loadData=True)
                 self.assertEqual(type(ict), icartt.Dataset)
 
     def testWriteHeader(self):
-        for fn in fns:
+        for fn in fns_pass:
             with self.subTest(msg=f"Writing header for test file {str(fn)}"):
                 ict = icartt.Dataset(fn, loadData=False)
-
                 strIn = open(fn)
                 strOut = io.StringIO()
-
                 ict.writeHeader(f=strOut)
-
                 self.assertTrue(compareFiles(fn, strIn, strOut, nlines=ict.nHeader))
 
     def testWrite(self):
-        for fn in fns:
+        for fn in fns_pass:
             with self.subTest(msg=f"Writing data for test file {str(fn)}"):
                 ict = icartt.Dataset(fn, loadData=True)
-
                 strIn = open(fn)
                 strOut = io.StringIO()
-
                 ict.write(f=strOut)
-
                 self.assertTrue(compareFiles(fn, strIn, strOut))
 
 
 if __name__ == "__main__":  # pragma: no cover
-    unittest.main()
\ No newline at end of file
+    unittest.main()