This paper proposes a software quality assessment framework for dependable systems (SQAF-DS), providing a systematic way to assess software quality through test cases, indirectly. SQAF-DS intends to reduce the time and cost for dependability assessment thorough using test cases as a means of the assessment. Test cases are developed in the process of software development and used to test target system, while dependability requirements are derived from dependability analysis, such as FTA (Fault Tree Analysis). SQAF-DS formally checks inclusion relation between dependability requirements and test cases. If the formal checking succeeds, then we can assure that the dependability requirements are well implemented in the software system.