Quick Scoop

System testing is the process of testing a fully integrated software application as one complete system to check whether it meets its requirements and works as expected. It usually happens after integration testing and before user acceptance testing (UAT).

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What it checks

• Functional behavior: whether the system does the right things for users.
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• Non-functional behavior: things like performance, security, reliability, and usability.
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• End- to-end flow: whether all integrated parts work together correctly.
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Why it matters

System testing helps catch issues that may not appear in unit or integration testing, especially problems that only show up when the whole product is working together. It reduces the chance of major defects reaching production.

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Simple example

For an online shopping app, system testing would check the full flow: sign in, search for a product, add it to the cart, pay, and receive an order confirmation.

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Stage	Focus
Unit testing	Individual functions or modules
Integration testing	How modules work together
System testing	The whole application as one complete system
Acceptance testing	Whether it is ready for users or the client

If you want, I can also give you a one-line definition, interview answer, or real-world example of system testing.