You are testing software which is being ported from one platform to another.

The type of test technique that is most useful in this situation is experience-based test technique. Experience-based test technique is a technique that relies on the knowledge and intuition of the testers to design and execute test cases based on their experience with similar systems or technologies. This technique is suitable for testing software that has no documented requirements and no time budgeted for writing them, as it can help to identify potential risks and defects based on past observations and lessons learned. Verified References: [ISTQB® Certified Tester Advanced Level Test Analyst CTAL-TA], Section 3.7.1, page 45.