test_that("cic returns correct structure", {
  set.seed(1)
  y_00 <- rnorm(100, 0, 1)
  y_01 <- rnorm(100, 0.5, 1)
  y_10 <- rnorm(50, 1, 1)
  y_11 <- rnorm(50, 2, 1)
  result <- cic(y_00, y_01, y_10, y_11)
  expect_s3_class(result, "cic")
  expect_true(!is.na(result$tau))
  expect_true(!is.na(result$se))
  expect_true(!is.na(result$pval))
  expect_equal(result$N, 300)
})

test_that("cic matches qte::CiC on workers comp data", {
  skip_if_not_installed("wooldridge")
  data("injury", package = "wooldridge")
  result <- cic(
    y_00 = injury$ldurat[injury$highearn == 0 & injury$afchnge == 0],
    y_01 = injury$ldurat[injury$highearn == 0 & injury$afchnge == 1],
    y_10 = injury$ldurat[injury$highearn == 1 & injury$afchnge == 0],
    y_11 = injury$ldurat[injury$highearn == 1 & injury$afchnge == 1]
  )
  # Known result from validation: tau = 0.0687
  expect_equal(round(result$tau, 2), 0.07, tolerance = 0.01)
})

test_that("cic with no treatment returns near-zero effect", {
  set.seed(42)
  y_00 <- rnorm(200, 0, 1)
  y_01 <- rnorm(200, 1, 1)  # time trend
  y_10 <- rnorm(200, 0, 1)  # same as control pre
  y_11 <- rnorm(200, 1, 1)  # same time trend, no treatment
  result <- cic(y_00, y_01, y_10, y_11)
  # With no treatment, tau should be near zero
  expect_lt(abs(result$tau), 0.5)
})

test_that("bootstrap SE is computed when requested", {
  set.seed(1)
  y_00 <- rnorm(50); y_01 <- rnorm(50)
  y_10 <- rnorm(30); y_11 <- rnorm(30)
  result <- cic(y_00, y_01, y_10, y_11, boot = TRUE, boot_iters = 100, seed = 42)
  expect_true(!is.na(result$boot_se))
  expect_gt(result$boot_se, 0)
})