There is general confusion on testing; for example:
Myth: All software must be completely tested to ensure defect-free software.
Fact: This is usually not possible or practical [see this video on Exhaustive Testing (2:32)]. Testing quantifies the risk of defects existing in untested software, but cannot prove that software is completely defect-free.
Myth: Quality Control is another name for Software Testing.
Fact: Testing is a subcomponent of Quality Control; Quality Control is a series of reactive checks and verifications through the software development process to ensure a high quality product.
Myth: Testing is overly expensive.
Fact: Testing is expensive; some global estimates place an average cost of around 50 billion dollars per year. But it is much less costly to fix defects found during testing than after the application goes live. Plus there are additional benefits by releasing high quality software, including business reputation.
Myth: Software testing is easy and can be learned by anyone.
Fact: Becoming a good tester requires analytical and deduction skills; many find they lack these skills and the motivation that are necessary to become an effective tester.
* It is important to note that the size and complexity of the software, number of testing resources, testing schedule/project deadlines all impact the types and amount of testing that can be successfully completed. Initial planning should consider all facts and devise an approach that maximizes or focuses the testing effort to provide the most value to the project, end users and the organization. This is covered more in the Approach section.