The Electronic Health Records (EHR) sharing system is the modern tool for delivering efficient healthcare to patients. Its functions include tracking of therapies, monitoring of the treatment effectiveness, prediction of outcomes throughout the patient's lifespan, and detection of human errors. For all the stakeholders, integrity and interoperability of the care continuum are paramount. Yet, its implementation is challenging due to the heterogeneity of healthcare information systems, security threats, and the enormousness of EHR data. To overcome these challenges, this work proposes BiiMED: a Blockchain framework for Enhancing Data Interoperability and Integrity regarding EHR-sharing. This solution is innovative as it contains an access management system allowing the exchange of EHRs between different medical providers and a decentralized Trusted Third Party Auditor (TTPA) for ensuring data integrity. This paper also discusses two validation techniques for enhancing the quality and correctness of the proposed solution: Formal Verification and Model-Based Techniques. The first one checks the correctness of a mathematical model describing the behavior of the given system prior to the implementation. The second technique derives test suites from the adopted model, performs them, and assesses the correctness.