[CSM-439]: Add unit tests for cache pull component

[boztopuz]

Linear: CSM-439

Adds a unit test suite for appcircle-cache-pull-component, following the conventions established in CSM-230, CSM-231 and the sibling CSM-417 cache push PR: a single self-executing test/test_main.rb, RSpec + Ruby stdlib only (no Gemfile/Bundler), the shared ReadableFormatter, and a coverage report printed after the run.

Results

✔  All 50 tests passed
main.rb  ████████████████████  100.0%  (70/70 lines)
merged from this process + 35 subprocess run(s)

What is covered

Both the positive and the negative path for every function in scope.

Function	Happy path	Negative / error branch
get_env_variable	returns the value, strips surrounding whitespace	missing key, empty string, whitespace-only → nil
run_command	command string passed to system untouched, silent on success	non-zero child status → @@[error] Unexpected exit with code N + SystemExit(0); nil → TypeError
run_command_with_log	logs @@[command], runs, prints took Ns	failure exits 0 and never prints took; nil → TypeError after logging; empty string
abort_with0	prints @@[error] <msg>, exits 0	empty and nil message still exit 0

Script-level behaviour, exercised by running main.rb in a subprocess:

• Env validation — AC_CACHE_LABEL, AC_TOKEN_ID and AC_CALLBACK_URL each have a missing and an empty test, asserting the @@[error] line, the deliberate exit code 0, and that the script stopped before doing any work. AC_REPOSITORY_DIR is asserted to be genuinely optional.
• AC_CACHE_GET_URL — this variable is set by main.rb from the getUrl field of the signed-URL response rather than supplied by the user, so it is covered through the curl target it produces: value present, getUrl absent from the JSON, getUrl empty, and a stale pre-set value being overwritten. Both provider branches are covered, including AC_CACHE_PROVIDER unset (confirming nil.eql? is safe here).
• Signed URL request — the composed ?action=getCacheUrls&cacheKey=…&tokenId=… query, empty response body skipping the download, and malformed JSON failing with a non-zero exit.
• Download and restore — label sanitization, exit 0 when the archive is absent or zero bytes, the MD5 digest and its appended .md5 sidecar, the top-level unzip, and the nested-archive loop that maps a cached folder named after an AC_ directory variable back to that path.

No real side effects

Kernel#system and Net::HTTP.get are replaced in the child through a RUBYOPT-preloaded stub, so no unzip, curl, rm or mkdir is ever executed and no socket is opened. Stubbed calls are echoed to stdout, which is what lets the tests assert the exact composed command strings. All fixtures live in Dir.mktmpdir and the script is run with chdir pointed at it, so nothing is written outside a temp directory.

Every mutation tried against main.rb while validating the suite (exit 0→exit 1, dropping --fail, loosening the label sanitizer, removing .strip, 'a'→'w' on the sidecar) was caught by at least one test.

Changes to main.rb

Only the if __FILE__ == $PROGRAM_NAME guard around the top-level script body, so the file can be required from the test. Reviewing with git diff -w shows the guard is the entire change — no logic, ordering or behaviour was touched. All four requires are stdlib, so no LoadError guards were needed.

Notes for the reviewer

Two pre-existing behaviours were found while writing the tests. Per the issue scope they are documented by the tests rather than changed, and are worth a look:

1. A zip sitting directly in the cache folder (ac_cache/<label>/foo.zip, no folder segment) resolves base_path to "", so the restore runs unzip … -d / and mkdir -p with no operand. Same for a folder that is not a known AC_ variable, which resolves to an absolute /<name>/.
2. unless ac_token_id.empty? (main.rb:66) can never be false — get_env_variable returns nil for an empty value and abort_with0 has already exited by that point.

How to run

gem install rspec   # once
ruby test/test_main.rb

🤖 Generated with Claude Code

[coderabbitai]

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