On a web based application, which set of tests is typically performed to ensure overall quality before release?

Introduction / Context:
Web based applications are accessed through browsers and serve a wide range of users, environments, and devices. Ensuring quality for such applications requires more than just checking basic functionality. Testers must consider aspects such as browser compatibility, performance under load, security vulnerabilities, and user experience. Interviewers often ask which types of tests are performed on web applications to evaluate a candidate's understanding of the broader quality landscape beyond simple functional testing.

Given Data / Assumptions:
- The question specifically deals with web based application testing.
- Web applications are accessed via different browsers, operating systems, screen sizes, and network conditions.
- Quality dimensions include functionality, usability, performance, security, and compatibility.
- The answer should reflect a comprehensive, realistic set of tests rather than a narrow or unrelated activity.

Concept / Approach:
For web applications, functional testing verifies that features such as login, search, and checkout work according to requirements. Usability testing evaluates how intuitive and user friendly the interface is. Performance testing checks response time, throughput, and scalability under different loads. Security testing looks for vulnerabilities such as injection attacks, cross site scripting, and weak authentication. Compatibility testing ensures that the application behaves correctly across major browsers, versions, and devices. The correct answer must mention several of these key categories, showing a realistic mix of tests applied to web applications.

Step-by-Step Solution:
Step 1: List the important quality dimensions for a modern web application: functionality, usability, performance, security, and compatibility.Step 2: Remember that web testing is not limited to server hardware or database aspects but includes end to end behaviour experienced by users.Step 3: Examine the options and look for one that groups these common types of testing together in a single answer.Step 4: Identify that option A mentions functional, usability, performance, security, and compatibility testing, matching the known set of web testing types.Step 5: Confirm that other options are too narrow or unrelated to realistic web application testing.

Verification / Alternative check:
Consider a typical e commerce web site. Testers verify that adding items to the cart and completing a purchase work correctly, which is functional testing. They perform usability checks to ensure that navigation and product search are intuitive. Performance tests simulate many users accessing the site at once to measure response times. Security tests probe for weaknesses such as insecure direct object references or unencrypted sensitive data. Compatibility tests open the site in different browsers and on mobile devices to ensure consistent behaviour. This combination of test types closely matches option A and reflects real world practice.

Why Other Options Are Wrong:
Option B focuses only on database indexing and server power supply, which are important infrastructure concerns but do not cover the full range of web testing. Option C speaks about office network printers and scanners, which are unrelated to web application quality. Option D describes checking only spelling of menu labels, missing crucial functional, performance, and security aspects. These options fail to represent a realistic and comprehensive test strategy for web applications.

Common Pitfalls:
A common mistake is to focus only on functional testing and ignore non functional aspects such as performance and security, which can severely affect user satisfaction and risk. Another pitfall is neglecting cross browser and device compatibility, leading to defects that appear only on particular platforms. Teams should plan a balanced test strategy that covers all major quality attributes. Automated tools can help with regression and performance tests, while usability and exploratory testing require careful human observation and feedback from real users.

Final Answer:
Correct answer: Functional, usability, performance, security, and compatibility testing of the web application