This book constitutes the refereed proceedings of the 20th IFIP TC 6/WG 6.1 International Conference on Testing Communicating Systems, TestCom 2008, and the 8th International Workshop on Formal Approaches to Testing of Software, FATES 2008, jointly held in Tokyo, Japan, in June 2008. The 18 revised full papers presented together with 2 invited talks were carefully reviewed and selected from initially 58 submissions to both events. The papers cover new approaches, concepts, theories, methodologies, tools, and experiences in the field of testing of communicating systems and general software. They are organized in topical sections on general software testing, testing continuous and real-time systems, network testing, test generation, concurrent system testing, and applications of testing.

Invited Talks.- All-IP Based Ultra 3G Network/Service Development in a Competitive Market.- Models and Testing - A Recipe for Improved Effectiveness?.- General Software Testing.- Runtime Verification of C Programs.- Test Construction for Mathematical Functions.- Model-Based Testing Service on the Web.- Testing Continuous and Real-Time Systems.- Using Disparity to Enhance Test Generation for Hybrid Systems.- Modeling Property Based Stream Templates with TTCN-3.- : A Timed Extension of .- Network Testing.- Model-Based Firewall Conformance Testing.- VCSTC: Virtual Cyber Security Testing Capability - An Application Oriented Paradigm for Network Infrastructure Protection.- Performance Test Design Process and Its Implementation Patterns for Multi-services Systems.- Test Generation.- Generating Checking Sequences for Partial Reduced Finite State Machines.- Testing Systems Specified as Partial Order Input/Output Automata.- Test Purpose Concretization through Symbolic Action Refinement.- Concurrent System Testing.- Implementation Relations for the Distributed Test Architecture.- Modular System Verification by Inference, Testing and Reachability Analysis.- Test Plan Generation for Concurrent Real-Time Systems Based on Zone Coverage Analysis.- Applications of Testing.- Applying Model-Based Testing to HTML Rendering Engines - A Case Study.- Model-Based Generation of Testbeds for Web Services.- Real-Time Testing with TTCN-3.