This dissertation presents a novel methodology based on test summaries, which characterize desired tests as constraints written in a mixed imperative and declarative notation, for automated systematic testing of relational applications, such as relational database engines. The methodology has at its basis two novel techniques for effective and efficient testing: (1) mixed-constraint solving, which provides systematic generation of inputs characterized by mixed-constraints using translations among different data domains; and (2) clustered test execution, which optimizes execution of test suites by leveraging similarities in execution traces of different tests using abstract-level undo operations, which allow common segments of partial traces to be executed only once and the execution results to be shared across those tests. A prototype embodiment of the methodology enables a novel approach for systematic testing of commonly used database engines, where test summaries describe (1) input SQL queries, (2) input database tables, and (3) expected output of query execution. An experimental evaluation using the prototype demonstrates its efficacy in systematic testing of relational applications, including Oracle 11g, and finding bugs in them. / text