The rapid evolution of generative artificial intelligence (GenAI) is transforming science education by facilitating innovative pedagogical paradigms while raising substantial concerns about scholarly integrity. One particularly pressing issue is the growing risk of student use of GenAI tools to outsource assessment tasks, potentially compromising authentic learning and evaluations. Addressing these challenges requires reflection on existing assessment practices and features. This position paper advances a conceptual framework for science assessment through the lens of "multimodality" and "interactivity." Multimodality emphasizes the use of diverse, organized semiotic resources for meaning making, while interactivity characterizes assessment environments where outcomes are shaped by students' actions. With the two dimensions, our multimodal interactive framework classifies assessments into four categories, with varying degrees of modality and interactivity. We argue that tasks with higher modality and interactivity can potentially overcome the concerns of GenAI on academic integrity. To further articulate this point, we provide concrete assessment examples for each category and explain how the prompt and response affordances in each assessment category help gauge students' understandings of key science constructs and identify tasks that are resistant or susceptible to AI-based outsourcing. We conclude by discussing how the framework serves as a meaningful analytical tool for educational researchers and practitioners. [This is the online first version of an article published in "Journal of Research in Science Teaching."]