Point Spread Function (PSF) modelling software. Using either a simple bivariate Gaussian, or PSFex.
Can model flux distributions in the image, or create a uniform flux distribution across an apparent magnitude range for a given zero point.
Using the modeled PSF and flux distribution can then inject a given number of fake sources into a supplied fits file.
Can create a catalog, listing x,y,flux(, mag: optional)
Can be used for mock transient hunting, image subtraction tests.