The article introduces a systematic method for creating functional test suites, known as the category-partition method. This method involves analyzing the system specification, writing formal test specifications, and using a generator tool to produce test descriptions from which test scripts are written. The advantages of this method include ease of modifying test specifications, control over test complexity and number, and the ability to maximize error detection. The method is applied to complex software systems, starting with decomposing the functional specification into independent functional units and identifying parameters and environment conditions. Categories and choices are then partitioned to maximize test effectiveness. Constraints are added to refine the test frames, and the final test specification is processed by a generator tool to produce test cases and scripts. The article also discusses the Test Specification Language (TSL) used to implement the method and provides an example of its application to a find command. The method is compared with other testing techniques and suggests future enhancements, including more flexible property specifications, generalized error and single tests, specifying test results, and automating test script generation.The article introduces a systematic method for creating functional test suites, known as the category-partition method. This method involves analyzing the system specification, writing formal test specifications, and using a generator tool to produce test descriptions from which test scripts are written. The advantages of this method include ease of modifying test specifications, control over test complexity and number, and the ability to maximize error detection. The method is applied to complex software systems, starting with decomposing the functional specification into independent functional units and identifying parameters and environment conditions. Categories and choices are then partitioned to maximize test effectiveness. Constraints are added to refine the test frames, and the final test specification is processed by a generator tool to produce test cases and scripts. The article also discusses the Test Specification Language (TSL) used to implement the method and provides an example of its application to a find command. The method is compared with other testing techniques and suggests future enhancements, including more flexible property specifications, generalized error and single tests, specifying test results, and automating test script generation.