✔ Test using empty files

Test edge cases + empty files, e.g. empty text content and a Unicode BOM character.

See also gh-79.

src/dinglehopper/tests/test_integ_empty_files.py

@@ -0,0 +1,35 @@
+from __future__ import division, print_function
+
+import math
+
+import pytest
+
+from .. import character_error_rate, plain_text
+from .util import working_directory
+
+
+@pytest.mark.integration
+@pytest.mark.parametrize(
+    "gt_file_content,ocr_file_content,cer_expected",
+    [
+        ("", "Lorem ipsum", math.inf),
+        ("Lorem ipsum", "", 1.0),
+        ("\ufeff", "Lorem ipsum", math.inf),
+        ("Lorem ipsum", "\ufeff", 1.0),
+        ("", "", 0.0),
+        ("\ufeff", "", 0.0),
+        ("", "\ufeff", 0.0),
+    ],
+)
+def test_empty_files(tmp_path, gt_file_content, ocr_file_content, cer_expected):
+    with working_directory(tmp_path):
+
+        with open("gt.txt", "w") as gtf:
+            gtf.write(gt_file_content)
+        with open("ocr.txt", "w") as ocrf:
+            ocrf.write(ocr_file_content)
+
+        gt_text = plain_text("gt.txt")
+        ocr_text = plain_text("ocr.txt")
+
+        assert character_error_rate(gt_text, ocr_text) == cer_expected