Check if the last Git commit has test coverage ############################################## :date: 2018-07-26T12:49:52Z :category: blog :tags: python,development,testing :url: 2018/07/26/check-if-last-git-commit-has-test-coverage/ :save_as: 2018/07/26/check-if-last-git-commit-has-test-coverage/index.html :status: published :author: Gergely Polonkai I use Python at work and for private projects. I also aim to write tests for my code, especially recently. And as I usually don’t start from 100% code coverage (TDD is not my game), I at least want to know if the code I just wrote have full coverage. The trick is to collect all the lines that changed, and all the lines that has no coverage. Then compare the two, and you have the uncovered lines that changed! Getting the list of changed lines ================================= Recently, I bumped into `this article `_. It is a great awk script that lists the lines that changed in the latest commit. I have really no problem with awk, but I’m pretty sure it can be done in Python, as that is my main language nowadays. .. code-block:: python def get_changed_lines(): """Get the line numbers that changed in the last commit """ git_output = subprocess.check_output('git show', shell=True).decode('utf-8') current_file = None lines = {} left = 0 right = 0 for line in git_output.split('\n'): match = re.match(r'^@@ -([0-9]+),[0-9]+ [+]([0-9]+),[0-9]+ @@', line) if match: left = int(match.groups()[0]) right = int(match.groups()[1]) continue if re.match(r'^\+\+\+', line): current_file = line[6:] continue if re.match(r'^-', line): left += 1 continue if re.match(r'^[+]', line): # Save this line number as changed lines.setdefault(current_file, []) lines[current_file].append(right) right += 1 continue left += 1 right += 1 return lines OK, not as short as the awk script, but works just fine. Getting the uncovered lines =========================== Coverage.py can list the uncovered lines with ``coverage report --show-missing``. For Calendar.social, this looks something like this: .. code-block:: log Name Stmts Miss Cover Missing ---------------------------------------------------------------------- calsocial/__init__.py 173 62 64% 44, 138-148, 200, 239-253, 261-280, 288-295, 308-309, 324-346, 354-363 calsocial/__main__.py 3 3 0% 4-9 calsocial/account.py 108 51 53% 85-97, 105-112, 125, 130-137, 148-160, 169-175, 184-200, 209-212, 221-234 calsocial/app_state.py 10 0 100% calsocial/cache.py 73 11 85% 65-70, 98, 113, 124, 137, 156-159 calsocial/calendar_system/__init__.py 10 3 70% 32, 41, 48 calsocial/calendar_system/gregorian.py 77 0 100% calsocial/config_development.py 11 11 0% 4-17 calsocial/config_testing.py 12 0 100% calsocial/forms.py 198 83 58% 49, 59, 90, 136-146, 153, 161-169, 188-195, 198-206, 209-212, 228-232, 238-244, 252-253, 263-267, 273-277, 317-336, 339-342, 352-354, 362-374, 401-413 calsocial/models.py 372 92 75% 49-51, 103-106, 177, 180-188, 191-200, 203, 242-248, 257-268, 289, 307, 349, 352-359, 378, 392, 404-409, 416, 444, 447, 492-496, 503, 510, 516, 522, 525, 528, 535-537, 545-551, 572, 606-617, 620, 652, 655, 660, 700, 746-748, 762-767, 774-783, 899, 929, 932 calsocial/security.py 15 3 80% 36, 56-58 calsocial/utils.py 42 5 88% 45-48, 52-53 ---------------------------------------------------------------------- TOTAL 1104 324 71% All we have to do is converting these ranges into a list of numbers, and compare it with the result of the previous function: .. code-block:: python def get_uncovered_lines(changed_lines): """Get the full list of lines that has not been covered by tests """ column_widths = [] uncovered_lines = {} for line in sys.stdin: line = line.strip() if line.startswith('---'): continue if line.startswith('Name '): match = re.match(r'^(Name +)(Stmts +)(Miss +)(Cover +)Missing$', line) assert match column_widths = [len(col) for col in match.groups()] continue name = [ line[sum(column_widths[0:idx]):sum(column_widths[0:idx]) + width].strip() for idx, width in enumerate(column_widths)][0] missing = line[sum(column_widths):].strip() for value in missing.split(', '): if not value: continue try: number = int(value) except ValueError: first, last = value.split('-') lines = range(int(first), int(last) + 1) else: lines = range(number, number + 1) for lineno in lines: if name in changed_lines and lineno not in changed_lines[name]: uncovered_lines.setdefault(name, []) uncovered_lines[name].append(lineno) return uncovered_lines At the end we have a dictionary that has filenames as keys, and a list of changed but uncovered lines. Converting back to ranges ========================= To make the final result more readable, let’s convert them back to a nice ``from_line-to_line`` range list first: .. code-block:: python def line_numbers_to_ranges(): """List the lines that has not been covered """ changed_lines = get_changed_lines() uncovered_lines = get_uncovered_lines(changed_lines) line_list = [] for filename, lines in uncovered_lines.items(): lines = sorted(lines) last_value = None ranges = [] for lineno in lines: if last_value and last_value + 1 == lineno: ranges[-1].append(lineno) else: ranges.append([lineno]) last_value = lineno range_list = [] for range_ in ranges: first = range_.pop(0) if range_: range_list.append(f'{first}-{range_[-1]}') else: range_list.append(str(first)) line_list.append((filename, ', '.join(range_list))) return line_list Printing the result =================== Now all that is left is to print the result on the screen in a format digestable by a human being: .. code-block:: python def tabular_print(uncovered_lines): """Print the list of uncovered lines on the screen in a tabbed format """ max_filename_len = max(len(data[0]) for data in uncovered_lines) for filename, lines in uncovered_lines: print(filename.ljust(max_filename_len + 2) + lines) And we are done. Conclusion ========== This task never seemed hard to accomplish, but somehow I never put enough energy into it to make it happen. Kudos to Adam Young doing some legwork for me!