A test plan serves multiple purposes, such as defining the scope, approach, resources, and schedule of the testing activities. It also helps in communicating important information and managing stakeholder expectations. In agile projects, test plans might be concise to align with agile principles of simplicity and flexibility. A one-page test plan can effectively communicate broad activities and strategic decisions, such as not writing detailed test cases due to the project's agile nature. This approach ensures that essential information is conveyed without unnecessary documentation overhead, adhering to the agile manifesto's value of "working software over comprehensive documentation".