  The x-ray emission of hot spots on the surface of neutron stars is the prime
target of the Neutron star Interior Composition Explorer (NICER). These x-ray
pulse profiles not only encode information of the bulk properties of these
stars, which teaches us about matter at supranuclear densities, but also about
the spacetime curvature around them which teaches us about relativistic
gravity. We explore the possibility of performing strong-gravity tests with
NICER observations using a recently developed pulse profile model beyond
general relativity. Our results suggest that NICER can place constraints on
deviations from general relativity due to an additional scalar degree of
freedom which are independent and competitive relative to constraints with
binary pulsar observations.
