Who Carries the Burden of Modularity? -- On Testing Message-Passing Components -- Composing Communicating Systems, Synchronously -- Modular Verification of JML Contracts Using Bounded Model Checking -- On Slicing Software Product Line Signatures -- Assumption-Commitment Types for Resource Management in Virtually Timed Ambients -- Abstraction and Genericity in Why3 -- Verification Artifacts in Cooperative Verification: Survey and Unifying Component Framework -- An Interface Theory for Program Verification -- Scaling Correctness-by-Construction -- X-by-Construction: Correctness meets Probability -- Correctness by construction for probabilistic programs -- Components in Probabilistic Systems: Suitable by Construction -- Behavioral Specification Theories: an Algebraic Taxonomy -- Approximating Euclidean by Imprecise Markov Decision Processes -- Shield Synthesis for Reinforcement Learning -- Inferring Performance From Code: A Review -- 30 years of Statistical Model Checking -- Statistical Model Checking: Black or White? -- Probabilistic Mission Planning and Analysis for Multi-agent Systems -- 30 Years of Simulation-Based Quantitative Analysis Tools: a Comparison Experiment between Möbius and Uppaal SMC -- Fluid Model-Checking in UPPAAL for Covid-19 -- Improving Secure and Robust Patient Service Delivery -- Verification and Validation of Concurrent and Distributed Systems (Track Summary) -- Step-wise Development of Provably Correct Actor Systems -- Violation Witnesses and Result Validation for Multi-Threaded Programs -- Tendermint Blockchain Synchronization: Formal Specification and Model Checking -- Safe Sessions of Channel Actions in Clojure: A Tour of the Discourje Project -- Modular Verification of Liveness Properties of the I/O Behavior of Imperative Programs -- Formal Verification of an Industrial Distributed Algorithm: an Experience Report -- Deploying TESTAR to enable remote testing in an industrial CI pipeline: a case-based evaluation -- A Formal Model of the Kubernetes Container Framework.

The three-volume set LNCS 12476 - 12478 constitutes the refereed proceedings of the 9th International Symposium on Leveraging Applications of Formal Methods, ISoLA 2020, which was planned to take place during October 20-30, 2020, on Rhodes, Greece. The event itself was postponed to 2021 due to the COVID-19 pandemic. The papers presented were carefully reviewed and selected for inclusion in the proceedings. Each volume focusses on an individual topic with topical section headings within the volume: Part I, Verification Principles: Modularity and (De-)Composition in Verification; X-by-Construction: Correctness meets Probability; 30 Years of Statistical Model Checking; Verification and Validation of Concurrent and Distributed Systems. Part II, Engineering Principles: Automating Software Re-Engineering; Rigorous Engineering of Collective Adaptive Systems. Part III, Applications: Reliable Smart Contracts: State-of-the-art, Applications, Challenges and Future Directions; Automated Verification of Embedded Control Software; Formal methods for DIStributed COmputing in future RAILway systems. .