Requirement specifications are important and one of the most reliable methods of insuring problems in a complex software project is to have poorly documented requirement specifications. Requirements are the details describing an application's externally perceived functionality and properties. Requirements should be clear, complete, reasonably detailed, cohesive, attainable and testable. A non-testable requirement would be, for example, "user-friendly", which is too subjective. A testable requirement would be something such as, "the product shall allow the user to enter their previously-assigned password to access the application". Care should be taken to involve all of a project's significant customers in the requirements process. Customers could be in-house or external and could include end-users, customer acceptance test engineers, testers, customer contract officers, customer management, future software maintenance engineers, salespeople and anyone who could later derail the project. If his/her expectations aren't met, they should be included as a customer, if possible. In some organizations, requirements may end up in high-level project plans, functional specification documents, design documents, or other documents at various levels of detail. No matter what they are called, some type of documentation with detailed requirements will be needed by test engineers in order to properly plan and execute tests. Without such documentation there will be no clear-cut way to determine if a software application is performing correctly.