Add hook to check the number of allowed lines

tests/check_number_of_lines_count_test.py

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