Testing - lesson 1 | HackIndia Skills

Key point

Test behaviour

A useful test proves something important your app does for a user. Do not start by asking “which files need tests?” Start by asking “what must not break?”

Recruiters trust tests when they protect real behaviour: login rules, price totals, form validation, permissions, API responses, and data changes.

What counts as worth testing

Your hackathon project does not need 100 tests. It needs a few tests that show you understand risk.

Pick things that are core to the app, easy to break while coding, or painful for users if wrong. A UPI split app must test amount splitting. A campus event app must test registration limits.

Your to-do

Find test ideas

Do each one yourself, then tap it to tick it off. The ticks are only a checklist for you: they are not marked or scored.

List 3 main user actions in your app.
Mark the action that affects money, marks, bookings, access, or saved data.
Write the happy path for that action: valid input and expected result.
Write 1 or 2 failure paths: invalid input, missing data, or not allowed.
Keep only tests where a bug would matter to a real user.

0 of 5 done

Example

Tiny test plan

Before writing test code, write a plain test plan in your repo. This keeps you focused when you add Jest, Pytest, Vitest, or any other tool later.

Feature: expense split

User action: Create a group expense

Worth testing:
1. Happy path
   Given amount = 900 and members = 3
   Expect each member share = 300

2. Rounding rule
   Given amount = 100 and members = 3
   Expect total assigned shares still equals 100

3. Invalid input
   Given amount = -50
   Expect the app rejects the expense

Not testing now:
- Button colour
- Exact wording of heading
- Animation timing

Common mistake

Do not test everything

Beginners often test easy things because they look quick: whether a heading renders, whether a function was called, or whether a variable exists.

Those tests may pass while the app is broken. Prefer testing the result the user or API gets.

Tip

Use AI carefully

You can ask ChatGPT, Gemini, or Claude to suggest test cases. Give it your feature, inputs, rules, and edge cases.

Check the answer. AI often suggests too many tests, tests private implementation, or ignores Indian product rules like rupee rounding, phone number format, or UPI-style flows.

Prompt:
I am building a college expense split app.
Feature: create expense.
Rules: amount is in rupees, members must be at least 2, shares must add up to the original amount.
Suggest 6 meaningful test cases.
Separate happy path, edge cases, and invalid input.
Do not suggest UI colour or layout tests.