testthat::test_that("MMBCV errors on missing required columns", {
  fake_fit <- list(
    cmap = matrix(1, nrow = 1, ncol = 1, dimnames = list("x", "1:2")),
    rmap = matrix(c(1, 1), ncol = 2),
    states = c("1", "2"),
    coefficients = 0
  )

  df <- data.frame(Tstart = 0, Tstop = 1, clus_id = 1, state = 2, x = 0.1)

  expect_error(
    MMBCV(fake_fit, df, StartTime = Tstart, StopTime = Tstop,
          Cluster = clus_id, Event = DOES_NOT_EXIST),
    "Missing required columns"
  )
})