Another edge case of encoding detection. #443

1 files changed, 13 insertions, 5 deletions

diff --git a/tests/test_phystokens.py b/tests/test_phystokens.py
index 7bdece72..e28fb176 100644
--- a/tests/test_phystokens.py
+++ b/tests/test_phystokens.py
@@ -102,6 +102,7 @@ ENCODING_DECLARATION_SOURCES = [
     b"#!/usr/bin/python\n# vim: set fileencoding=cp850:\n",
     b"# This Python file uses this encoding: cp850\n",
     b"# This file uses a different encoding:\n# coding: cp850\n",
+    b"\n# coding=cp850\n\n",
 ]
 
 class SourceEncodingTest(CoverageTest):
@@ -126,11 +127,6 @@ class SourceEncodingTest(CoverageTest):
         source = b'def parse(src, encoding=None):\n    pass'
         self.assertEqual(source_encoding(source), DEF_ENCODING)
 
-    def test_detect_source_encoding_on_second_line(self):
-        # A coding declaration should be found despite a first blank line.
-        source = b"\n# coding=cp850\n\n"
-        self.assertEqual(source_encoding(source), 'cp850')
-
     def test_dont_detect_source_encoding_on_third_line(self):
         # A coding declaration doesn't count on the third line.
         source = b"\n\n# coding=cp850\n\n"
@@ -160,6 +156,18 @@ class NeuterEncodingDeclarationTest(CoverageTest):
         for source in ENCODING_DECLARATION_SOURCES:
             neutered = neuter_encoding_declaration(source.decode("ascii"))
             neutered = neutered.encode("ascii")
+
+            # The neutered source should have the same number of lines.
+            source_lines = source.splitlines()
+            neutered_lines = neutered.splitlines()
+            self.assertEqual(len(source_lines), len(neutered_lines))
+
+            # Only one of the lines should be different.
+            lines_different = sum(
+                int(nline != sline) for nline, sline in zip(neutered_lines, source_lines)
+            )
+            self.assertEqual(lines_different, 1)
+
             self.assertEqual(
                 source_encoding(neutered),
                 DEF_ENCODING,