Testing Approaches

1. Black Box Testing 🖤

   • You don’t look inside the system.

   • You just test the input and output.

   • Example: You enter your username & password and check if login works — without caring how the code is written.

2. White Box Testing 🤍

   • You look inside the code and test it.

   • You check logic, loops, conditions, and flows.

   • Example: You test if an if-else condition in the login function works correctly.

3. Grey Box Testing 🩶

   • A mix of both.

   • You know some details of the code (not everything).

   • Example: You know the login system uses encryption, so you test both the functionality (black box) and a bit of the inner working (like encryption handling).

Let’s use an ATM machine example:

• Black Box Testing

  • You insert your card, enter PIN, withdraw money.

  • You don’t know how the ATM is processing your request inside.

  • You just check if the machine gives you the right amount of cash.

• White Box Testing

  • Imagine you are the engineer who built the ATM software.

  • You open the code and test things like:

    • Is the PIN validation working correctly?

    • Is the balance check logic right?

    • Is the withdrawal logic secure?

• Grey Box Testing

  • You are not a customer, but not the full developer either.

  • Maybe you’re a bank’s tester who knows the ATM uses a database and encryption.

  • You test not only the cash withdrawal but also check:

    • Is the database updated after withdrawal?

    • Is the encryption working for PIN storage?