check_for_tests.py

#find serverless dir
from pathlib import Path
serverless_dir = Path("./serverless")

if not serverless_dir.exists():
    raise

#find all of the folders in the root of serverless
#except those that don't have customer-facing code
skipped_dirs = ["node_modules", ".git", "docs", ".github", "test"]
production_dirs = []
for f in serverless_dir.iterdir():
    if f.is_dir() and not (f.stem in skipped_dirs):
        production_dirs.append(f)

#then check all those dirs for .js files
js_files = []
for p_dir in production_dirs:
    js_files.extend( list(p_dir.glob('**/*.js')) )

#then find all test files in the `test` directory
test_dir = serverless_dir / "test"

if not test_dir.exists():
    raise

test_files = list(test_dir.glob('**/*.test.js'))

#then with the list of .js files, check for tests with the format: <name of js file>.test.js
#we will adopt a strategy of using sets
#the test file paths in `test_files` are of the format: 'serverless/test/<test subdir>/<some>/<path>/<name of js file>.test.js'
#this mimics the path to the file each test corresponds to; for example: 'serverless/lib/<some>/<path>/<name of js file>.js'
#so if we can transform the former, into the format of the later (changing `<name of js file>.test.js` to `<name of js file>.js`)
#and strip off the `serverless/test/<test subdir>` and `serverless` respectively
#then the path string for the js files found previously, and the transformed path string for each test should match
#therefore we can then add the transformed path strings for the tests to a set, and the path strings for the files to a different set
#and find the difference
#this should show which .js files do not have corresponding test files

#transforming the list of .js files
from pathlib import Path
import os

transformed_js_files = []
for f in js_files:
    trunc = list(f.parts)[1:] #strip off `serverless`
    transformed_js_files.append( Path(os.path.join(*trunc)) ) #recreate the now-truncated path

#transforming the list of test files

transformed_test_files = []
for f in test_files:
    #strip off the end of string containing the suffixes for each test file
    #for example: <name of test file>.test.js
    #see: https://stackoverflow.com/questions/1038824/how-do-i-remove-a-substring-from-the-end-of-a-string
    new_name = f.name[:-len("".join(f.suffixes))]
    new_name += f.suffixes[-1] #re-add the .js to each file name
    _f = f.with_name(new_name)

    trunc = list(_f.parts)[3:] #strip off `serverless/test/<test subdir>`
    
    if len(trunc) == 0: #ignore files in the root of serverless/test
        continue
    
    transformed_test_files.append( Path(os.path.join(*trunc)) ) #recreate the now-truncated path

set_transformed_js_files = set(transformed_js_files)
set_transformed_test_files = set(transformed_test_files)

diff = set_transformed_js_files - set_transformed_test_files

assert all([Path("serverless" / f).exists() for f in diff]) #sanity check, all such files exist

import json
print(json.dumps(sorted([str(f) for f in diff]), indent = 4) )

This code assumes a clone of the serverless code in a folder serverless in the same directory as the script. It should list (in JSON) all files without tests; Where the path of each such files is relative to the root of the serverless folder.

Tested with Python 3.8.