NASA is evolving a long-term strategy to pioneer space to expand human and robotic presence farther into the solar system, not just to explore and visit, but to stay. NASA's strategy is designed to meet technical and non-technical challenges, leverage current and near-term activities, and lead to a future where humans can work, learn, operate, and thrive safely in space for an extended, and eventually indefinite, period of time. An important aspect of this strategy is the implementation of proving ground activities needed to ensure confidence in both Mars systems and deep space operations prior to embarking on the journey to Mars. As part of the proving ground development, NASA is assessing potential mission concepts that could validate the required capabilities needed to expand human presence into the solar system. An initial step in the proving ground is to establish human presence in cislunar space to enable development and testing of systems and operations required to enable crewed Mars missions in the 2030s and safely explore other deep space destinations. These capabilities may also be leveraged to support potential commercial and international objectives for lunar surface missions. This paper will identify a series of potential proving ground missions and flight test objectives that support NASA on the journey to Mars and can be leveraged for commercial and international goals. The paper will discuss how early missions will begin to satisfy these objectives, including extensibility and applicability to Mars exploration systems and operations. The initial capability provided by NASA's Space Launch System will be described as well as planned upgrades required to support longer and more complex missions. Potential architectures and mission concepts will be examined as options to satisfy proving ground objectives. In addition, commercial and international participation opportunities will be assessed on their ability to enable the development of exploration capabilities and operations applicable to Mars vicinity and surface missions.