Which factor most significantly affects the testing effort for a software product?

The requirements for reliability and security in a product significantly impact the testing effort because they dictate the scope and depth of testing required. High demands for reliability typically mean that extensive testing needs to be conducted to ensure that the software consistently performs as expected under various conditions. In addition, if security is a crucial requirement, it often necessitates specialized tests, such as vulnerability assessments and penetration testing, to identify potential weaknesses before the product is released.

When these requirements are stringent, the testing effort increases in terms of the number of test cases needed, the complexity of the scenarios that need to be executed, and the skills required from the testing team. As a result, both the time and resources allocated for testing may rise considerably to meet these specific and high standards, making reliability and security key factors in shaping the overall testing strategy.