Why your Telegram bot test is failing silently

Telegram app logo is seen in this illustration taken, Aug 27, 2024.
Image: Reuters file

Sometimes the problem isn’t in your test code — it’s in how Telegram handles updates.

If your bot is running locally in polling mode, and your test also tries to read updates — nothing will break… but nothing will work either.

Let me explain what happened — and why this behavior is easy to overlook when you're just starting to test Telegram bots as myself.

The Problem

I was writing a test for the /start command using pytest.
The bot was running locally, the token was valid, everything looked fine — but the test was just...waiting.

Turns out, the issue wasn’t in the code — it was in the way Telegram’s getUpdates API works.

Here’s what was really going on:

My bot was running with .run_polling(), which continuously polls getUpdates in the background.
My test was also calling getUpdates manually, expecting to retrieve the /start command from a real Telegram chat.
The result? A hidden conflict.

Telegram only allows one active consumer of updates.

So when the bot is running, it “eats” all updates — and the test sees nothing.

🛠️ How to Fix It

Since you can’t simulate a user sending /start directly through the Telegram API (that’s forbidden), here are two reliable alternatives:

Option 1: Manual Trigger + Stored Log Verification
Best for CI or webhook-based bots.

You manually send /start from Telegram.
Your bot processes it and logs the result.
Your test waits briefly, then checks the log file or database to confirm the expected output.

Option 2: Simulate Telegram webhook with a fake payload

A fully automated way using requests.post() or similar to mock a real Telegram update:

You run your bot in webhook mode (instead of polling).
Telegram would normally send POST requests to your webhook URL (e.g. https://abc123.ngrok-free.app/webhook)
Instead, your test simulates this POST request using your own payload.
Your Flask or FastAPI app receives it and behaves as if it came from Telegram.

But why do I need Flask or FastAPI at all?

When using webhooks, Telegram sends updates to your bot as HTTP POST requests.

To receive them — you need a web server.

That’s where Flask or FastAPI comes in.
They expose an endpoint like /webhook that can receive and process Telegram’s payloads.

Webhook flow:

1. Telegram sends an update: POST https://yourdomain.com/webhook
2. Flask/FastAPI receives it and hands it over to python-telegram-bot
3. Your handler function is called just like in polling mode

Without this, your bot simply won’t work in webhook mode — and you won’t be able to test real-world flows in CI/CD.

Testing Telegram bots has its nuances and bottlenecks, and this one was a surprise for me too.

But the deeper you go — the more power you unlock.
This case alone pushed me to explore better testing strategies and architect a more production-like setup, even for test automation.

Would you be interested in more deep-dives on Telegram bot testing?

Let me know in the comments or drop a DM — I’m currently building a courses on this topic using Pytest, Playwright, and Cypress.