Test for bias due to index shifting

[pratikunterwegs]

Can I suggest to add a test that

cfr_time_varying(
  data = df_covid_uk,
  burn_in = 7L
)

yields the same result as

cfr_time_varying(
  data = df_covid_uk,
  delay_density = \(x) ifelse(x == 0, 1, 0), 
  burn_in = 7L
)

to make sure your implementation doesn't introduce any bias due to index shifting?

Originally posted by @sbfnk in #103 (comment)