Use pyfakefs instead of real files in tests

* adjust review findings

README.md

@@ -59,8 +59,8 @@ Attempts to load all json files to verify syntax.
 Check for files that contain merge conflict strings.
 
 #### `check-number-of-lines-count`
-Check if number of lines of a file is greater than a threshold. You can
+Check if the number of lines of a file is greater than a threshold.
-configure this with the following commandline option:
+You can configure this with the following command line option:
   - `--max-lines N` - maximum number of lines allowed in a file.
 
 #### `check-shebang-scripts-are-executable`

pre_commit_hooks/check_number_of_lines_count.py

@@ -12,7 +12,7 @@ def main(argv: Optional[Sequence[str]] = None) -> int:
         default=30,
         type=int,
         action='store',
-        help='Maximum allowable number of lines (default: 30)',
+        help='Maximum allowed number of lines',
     )
     args = parser.parse_args(argv)
 

requirements-dev.txt

@@ -1,3 +1,4 @@
 covdefaults
 coverage
+pyfakefs
 pytest

tests/check_number_of_lines_count_test.py

@@ -1,31 +1,29 @@
 from pre_commit_hooks.check_number_of_lines_count import main
 
 
-def test_number_of_lines_count_bad(tmpdir):
+def test_number_of_lines_count_bad(fs):
-    max_lines = 30
+    max_lines = 42
-    line_contents = []
-    filename = tmpdir.join('lines_count_bad')
 
-    for line_number in range(max_lines + 1):
+    filename = 'lines_count_bad'
-        line_contents.append(f'I am the {line_number+1}. line!')
+    line_contents = [
-
+        f'I am the {line_number+1}. line!'
-    with open(filename, 'w') as file:
+        for line_number in range(max_lines + 1)
-        file.write('\n'.join(line_contents))
+    ]
+    fs.create_file(filename, contents='\n'.join(line_contents))
 
     ret = main([str(filename), f'--max-lines={max_lines}'])
     assert ret == 1
 
 
-def test_number_of_lines_count_good(tmpdir):
+def test_number_of_lines_count_good(fs):
-    max_lines = 30
+    max_lines = 42
-    line_contents = []
-    filename = tmpdir.join('lines_count_good')
 
-    for line_number in range(max_lines):
+    filename = 'lines_count_good'
-        line_contents.append(f'I am the {line_number+1}. line!')
+    line_contents = [
-
+        f'I am the {line_number+1}. line!'
-    with open(filename, 'w') as file:
+        for line_number in range(max_lines)
-        file.write('\n'.join(line_contents))
+    ]
+    fs.create_file(filename, contents='\n'.join(line_contents))
 
     ret = main([str(filename), f'--max-lines={max_lines}'])
     assert ret == 0