Beyond the surface
A website can look perfect and still be a disaster for a user. In this level, we focus on Input Validation. This is where most functional bugs hide.
Input Validation: The process of ensuring that a program operates on clean, correct and useful data. As a tester, your job is to provide the "dirty" data and see if the system handles it gracefully.
What we're hunting now:
- Required Fields: Can I submit the form if I leave "Email" empty?
- Data Types: Can I type my name into a "Phone Number" field?
- Boundary Values: If a password must be 8 characters, does it work with 7? What about 8? What about 8,000?
- State Gaps: Can I "Confirm Order" before I've even selected a shipping method?
What is a test case?
A test case is a set of conditions or variables under which a tester will determine whether a system under test satisfies requirements. Without an expected result, you just have a set of steps with no verdict.
| Test ID | TC-001 |
| Preconditions | User is on the Registration page. |
| Test Steps | 1. Enter valid email. 2. Leave "Password" field empty. 3. Click "Submit". |
| Expected Result | Error message "Password is required" is shown; User is not registered. |
| Actual Result | [To be filled in during execution] |
The "Happy Path" Trap
Junior testers often fall into the trap of only testing the Happy Path — the sequence of actions where everything goes right. Professional testing spends 80% of its time on the Edge Cases.
"A user walks into a bar. Orders a beer. Orders 0 beers. Orders 999999999 beers. Orders a lizard. Orders -1 beers. Orders a sfdeljkghs."
Techniques you'll use:
In the next section, you'll learn Equivalence Partitioning and Boundary Value Analysis. These are the two most powerful tools in a Junior tester's kit for finding logic bugs without testing every single possible input.
Here's a taste of both before you hit the techniques page:
Equivalence Partitioning — age field example (18–65):
| Partition | Example value | Expected |
|---|---|---|
| Below minimum (under 18) | 10 | Rejected |
| Valid range (18–65) | 40 | Accepted |
| Above maximum (over 65) | 70 | Rejected |
Boundary Value Analysis — the exact edges of that same range:
| Test value | At boundary? | Expected |
|---|---|---|
| 17 | Just below min | Rejected |
| 18 | Minimum | Accepted |
| 65 | Maximum | Accepted |
| 66 | Just above max | Rejected |
The next 10 practice pages are all forms — login, registration, checkout, search, date picker, file upload, profile, password reset, quantity inputs, and a multi-step wizard. Every bug type you'll face in this level comes from form validation.
Modern QE: The AI Advantage
In 2026, Junior Testers don't just write test cases manually. They use AI Co-pilots to:
- Generate Test Data: Create 1,000 unique valid/invalid emails in seconds.
- Expand Test Ideas: Ask AI "What are the edge cases for a New Zealand date picker?"
- Explain Code: Paste a snippet of form logic and ask AI to find the boundary error.
Note: You still need to understand the logic (EP/BVA) to know if the AI's suggestions are actually correct!