Several of the automatic tests include checks on whether Calkulate does self-consistent calibrations, for example solving a sample where the titrant was calibrated with itself, which should return exactly the correct alkalinity.
So if the Tests badge below says "passing":
then these validation checks are working for the currently released version.
All of the equilibrium constants and salt concentrations estimated from salinity are determined with PyCO2SYS v1.6.0 and therefore guaranteed to be identical to the values used there. See the PyCO2SYS validation docs for more information on how these themselves are validated.