test_that("test resample", {
  df <- data.frame(
    sex = as.factor(c(rep("M", 5), rep("F", 5), rep("N", 5))),
    target = c(1, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1)
  )

  MN <- sum(df$sex == "M" & df$target == 0)
  MP <- sum(df$sex == "M" & df$target == 1)
  FN <- sum(df$sex == "F" & df$target == 0)
  FP <- sum(df$sex == "F" & df$target == 1)
  NN <- sum(df$sex == "N" & df$target == 0)
  NP <- sum(df$sex == "N" & df$target == 1)

  weights <- reweight(df$sex, df$target)

  wMP <- weights[1]
  wMN <- weights[5]
  wFP <- weights[10]
  wFN <- weights[6]
  wNN <- weights[13]
  wNP <- weights[15]

  # expected
  E_MP <- round(MP * wMP)
  E_MN <- round(MN * wMN)
  E_FN <- round(FN * wFN)
  E_FP <- round(FP * wFP)
  E_NP <- round(NP * wNP)
  E_NN <- round(NN * wNN)

  # uniform
  df_2 <- df[resample(df$sex, df$target), ]

  MN_2 <- sum(df_2$sex == "M" & df_2$target == 0)
  MP_2 <- sum(df_2$sex == "M" & df_2$target == 1)
  FN_2 <- sum(df_2$sex == "F" & df_2$target == 0)
  FP_2 <- sum(df_2$sex == "F" & df_2$target == 1)
  NN_2 <- sum(df_2$sex == "N" & df_2$target == 0)
  NP_2 <- sum(df_2$sex == "N" & df_2$target == 1)

  expect_equal(E_MP, MP_2)
  expect_equal(E_MN, MN_2)
  expect_equal(E_FP, FP_2)
  expect_equal(E_FN, FN_2)
  expect_equal(E_NP, MP_2)
  expect_equal(E_NN, NN_2)

  # preferential
  df <- data.frame(
    sex = as.factor(c(rep("M", 5), rep("F", 5), rep("N", 5))),
    target = c(1, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1),
    name = as.character(1:15),
    probs = c(0.9, 0.82, 0.56, 0.78, 0.45, 0.12, 0.48, 0.63, 0.48, 0.88, 0.34, 0.12, 0.34, 0.49, 0.9),
    stringsAsFactors = FALSE
  )

  df_3 <- df[resample(df$sex, df$target, type = "preferential", probs = df$probs), ]

  expect_equal(sort(as.numeric(df_3$name)), c(1, 2, 5, 5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 15))

  expect_error(resample(df$sex, df$target, type = "preferential", probs = df$probs, cutoff = 12))
  expect_error(resample(df$sex, df$target, type = "preferential", probs = df$probs, cutoff = c(0.3, 0.4)))
})