Add line splitting and file reading

Add some tests around reading lines and striping UTF BOMs

tests/unit/test_file_checker.py

@@ -0,0 +1,26 @@
+"""Tests for the FileChecker class."""
+from flake8 import checker
+
+import pytest
+
+
+def test_read_lines_splits_lines():
+    """Verify that read_lines splits the lines of the file."""
+    file_checker = checker.FileChecker(__file__, [])
+    lines = file_checker.read_lines()
+    assert len(lines) > 5
+    assert '"""Tests for the FileChecker class."""\n' in lines
+
+
+@pytest.mark.parametrize('first_line', [
+    '\xEF\xBB\xBF"""Module docstring."""\n',
+    '\uFEFF"""Module docstring."""\n',
+])
+def test_strip_utf_bom(first_line):
+    r"""Verify that we strip '\xEF\xBB\xBF' from the first line."""
+    lines = [first_line]
+    file_checker = checker.FileChecker('stdin', [])
+    file_checker.lines = lines[:]
+    file_checker.strip_utf_bom()
+    assert file_checker.lines != lines
+    assert file_checker.lines[0] == '"""Module docstring."""\n'