Cross-coverage of a program P refers to the test coverage measured over a different program Q that is functionally equivalent to P. The novel concept of cross-coverage can find useful applications in the test of redundant software. We apply here cross-coverage for test suite augmentation and show that additional test cases generated from the coverage of an equivalent program, referred to as cross tests, can increase the coverage of a program in more effective way than a random baseline. We also observe that -contrary to traditional coverage testing-cross coverage could help finding (artificially created) missing functionality faults.