Things don't always work as intended. Some devices are manufactured incorrectly, others break or wear out after extensive use. In order to determine if a device was manufactured correctly, or if it continues to function as intended, it must be tested. The test is an evaluation based on a set of requirements. Depending on the complexity of the product, the test may be a mere perusal of the product to determine whether it suits one's personal whims, or it could be a long, exhaustive checkout of a complex system to ensure compliance with many performance and safety criteria. Emphasis may be on speed of performance, accuracy, or reliability.
Consider the automobile. One purchaser may be concerned simply with color and styling, another may be concerned with how fast the automobile accelerates, yet another may be concerned solely with reliability records. The automobile manufacturer must be concerned with two kinds of test. First, the design itself must be tested for factors such as performance, reliability, and serviceability. Second, individual units must be tested to ensure that they comply with design specifications.
Testing will be considered within the context of digital logic. The focus will be on technical issues, but it is important not to lose sight of the economic aspects of the problem. Both the cost of developing tests and the cost ...