The software testing life cycle (STLC) is a sequence of specific activities conducted during the testing process to ensure software quality. Key phases include Requirements Analysis, Test Planning, Test Case Development, Environment Setup, Test Execution, and Test Cycle Closure. During these phases, test objectives are defined, test cases are designed, environments are prepared, test cases are executed, and test results are analyzed to ensure the software meets quality standards.

Verification is the process of evaluating work-products of a development phase to ensure the software is being built correctly. It involves checking documents, design, code, and program to ensure they follow certain standards. Validation, on the other hand, is the process of evaluating the final product to check whether it meets the business needs and requirements. Essentially, verification checks if you're building the product right, and validation checks if you're building the right product.

Managing test cases efficiently is crucial, and tools like TestRail or JIRA can be instrumental. Begin by understanding requirements and creating test scenarios. Break these into granular test cases and prioritize them based on risk and impact. Ensure traceability by mapping test cases to requirements and update them as the project evolves. Use coverage metrics like requirement coverage and code coverage to quantify how much of the application is being tested, which helps in identifying gaps in test coverage.

A Test Oracle is a mechanism used to determine whether a software test has passed or failed. It could be a document, methodology, or an existing system that helps testers ascertain the expected behavior. Essentially, a Test Oracle provides the correct expected result, against which the actual result is compared. For example, in automated testing, Test Oracles can be a set of assertions or checkpoints to verify that the application behaves as expected.

When a bug is found, the Test Engineer's role is to document it thoroughly and clearly in the bug tracking system, providing detailed steps to reproduce, expected and actual results, severity, and any relevant screenshots or logs. It's also crucial to communicate the bug to the development team and collaborate to understand the underlying issue. After a fix is made, the Test Engineer should verify the fix and conduct regression testing to ensure the fix doesn't impact other parts of the application.

Approaching performance testing for a web application involves several steps. Start by identifying performance criteria and key scenarios that need testing. Use tools like JMeter or LoadRunner to simulate user load and measure metrics such as response time, throughput, and resource utilization. Analyze the results to identify bottlenecks or areas needing optimization. It's crucial to include both load testing and stress testing to understand the application behavior under various conditions. Regularly update performance tests to reflect changes in the application or architecture.