data <- dplyr::select(mtcars, cyl, mpg, disp, vs) |>
  dplyr::mutate(vs = factor(vs, levels = c("0", "1", "2")))

set.seed(20231218)
start_data <- dplyr::select(data, cyl, vs) |>
  dplyr::slice_sample(n = 20)

# roadmap
roadmap <- roadmap(
  conf_data = data,
  start_data = start_data
) |>
  add_sequence_manual(mpg, disp)

# synth_spec
step1 <- function(x) {
  recipes::step_center(x, recipes::all_numeric_predictors())
}

rpart_mod_cat <- parsnip::decision_tree() |> 
  parsnip::set_mode("classification") |>
  parsnip::set_engine("rpart")

rpart_mod_num <- parsnip::decision_tree() |>
  parsnip::set_mode("regression") |>
  parsnip::set_engine("rpart")


synth_spec <- synth_spec(
  default_regression_model = rpart_mod_num,
  default_classification_model = rpart_mod_cat,
  default_regression_steps = step1, 
  default_classification_steps = step1, 
  default_regression_sampler = sample_rpart,
  default_classification_sampler = sample_rpart,
  default_regression_noise = noise(
    add_noise = TRUE,
    noise_func = add_noise_kde,
    exclusions = c(0, 100),
    n_ntiles = 4
  ),
  default_classification_noise = noise(add_noise = FALSE)
)


# constraints
constraints_df_num <- tibble::tribble(
  ~var, ~min, ~max, ~conditions,
  "mpg", 0, Inf, "TRUE",
  "mpg", -Inf, 15, "cyl == 6",
  "mpg", -Inf, 12, "cyl == 8",
  "disp", 0, Inf, "TRUE"
) 

constraints <- constraints(
  schema = roadmap$schema,
  constraints_df_num = constraints_df_num,
  max_z_num = 0
)

test_that("synthesize() runs without error with empty factor levels", {
  
  expect_warning(
    presynth <- presynth(
      roadmap = roadmap |>
        add_constraints(constraints),
      synth_spec = synth_spec
    )
  )
  
  synth <- synthesize(presynth)
  
  # expect synthesis output properly formatted
  expect_true(is_postsynth(synth))
  expect_equal(nrow(roadmap$start_data), nrow(synth$synthetic_data))
  
  expect_type(synth$synthetic_data$mpg, "double")
  expect_type(synth$synthetic_data$disp, "double")
  expect_true(is.factor(synth$synthetic_data$vs))
  
  expect_equal(dim(synth$ldiversity), c(20, 2))
  expect_equal(names(synth$ldiversity), 
               presynth$roadmap$visit_sequence$visit_sequence)
  
  # expect empty factor levels handled as expected
  expect_identical(
    levels(roadmap$conf_data$vs),
    levels(synth$synthetic_data$vs)
  )
  
  expect_true(all(synth$synthetic_data$vs != "2"))
  
})