Excellent one!
The testing basics are basic tenets that guide the testers as to how to test and why testing is done. These were formulated by the ISTQB (International Software Testing Qualifications Board) and are universally adopted in the software sector.
 7 Software Testing Basics
1. Testing Reveals the Existence of Defects, Not Their Absence
Testing can reveal defects, but it cannot prove that the software is 100% bug-free.
Even after thorough testing, there may still be undiscovered defects.
Example: You can test an app and find no errors — but that doesn’t mean none exist; maybe you just didn’t test the right conditions.

2. Exhaustive Testing is Impossible
It’s not practical to test all possible inputs, combinations, and paths in an application.
Instead, the testers do risk-based and priority-based testing.
 Example: You can't test every possible password a user could input; you test common and edge cases instead.

3. Early Testing Saves Time and Money
Testing must begin as early as possible within the Software Development Life Cycle (SDLC).
Finding and fixing defects early is much more cost-effective than discovering them after release.
Example: Detecting a design flaw in the planning phase costs much less than correcting it in production.

4. Defects Cluster Together
The majority of defects reside in a few modules in most software.
Testers can concentrate more effort on high-risk or failing most often sections.
Example: The payment module of an e-commerce website has more problems than static pages.

5. Pesticide Paradox
Repeating the same tests over and over again will eventually stop discovering new bugs.
In order to continue testing effectively, test cases must be updated and re-examined regularly.
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