test_that("fourier_test works with 3 variables", {
  set.seed(42)
  n <- 200
  e <- matrix(rnorm(n * 3), n, 3)
  x1 <- cumsum(e[,1])
  x2 <- cumsum(e[,2])
  brk <- 5 * sin(2 * pi * (1:n) / n)
  y <- brk + 0.5 * x1 + 0.3 * x2 + cumsum(0.1 * e[,3])
  dat <- cbind(y, x1, x2)

  result <- fourier_test(dat, model = 3, k = 2, freq = 1)

  expect_s3_class(result, "fjcoint")
  expect_equal(result$test, "fourier")
  expect_equal(result$nvars, 3)
  expect_equal(length(result$trace), 3)
  expect_equal(length(result$lambda), 3)
  expect_equal(length(result$cv_trace), 3)
  expect_true(all(result$eigenvalues >= 0))
  expect_true(all(result$eigenvalues < 1))
  # Log-L should be monotonically increasing
  for (i in 2:length(result$logL)) {
    expect_true(result$logL[i] >= result$logL[i - 1] - 0.001)
  }
})

test_that("fourier_test works with cumulative frequencies", {
  set.seed(123)
  n <- 200
  e <- matrix(rnorm(n * 2), n, 2)
  y <- cumsum(e[,1])
  x <- cumsum(e[,2])
  dat <- cbind(y, x)

  result <- fourier_test(dat, model = 1, k = 2, freq = 2,
                          option = "cumulative")
  expect_s3_class(result, "fjcoint")
  expect_equal(result$option, "cumulative")
  expect_equal(result$freq, 2)
})

test_that("fourier_test rejects bad inputs", {
  expect_error(fourier_test(matrix(1:10, 10, 1)), "between 2 and 5")
  expect_error(fourier_test(matrix(1:20, 10, 2), model = 5), "1-4")
  expect_error(fourier_test(matrix(1:20, 10, 2), freq = 6), "1-5")
})

test_that("sbc_test works", {
  set.seed(42)
  n <- 200
  e <- matrix(rnorm(n * 3), n, 3)
  x1 <- cumsum(e[,1])
  x2 <- cumsum(e[,2])
  y  <- 0.5 * x1 + 0.3 * x2 + cumsum(0.1 * e[,3])
  dat <- cbind(y, x1, x2)

  result <- sbc_test(dat, maxlag = 2, maxfreq = 2)

  expect_s3_class(result, "fjcoint")
  expect_equal(result$test, "sbc")
  expect_equal(length(result$ranks), 3) # m ranks (0, 1, 2)
  expect_true(all(result$selected %in% c("Johansen", "SC-VECM", "Fourier")))
})

test_that("fjcoint dispatcher works", {
  set.seed(42)
  n <- 200
  e <- matrix(rnorm(n * 2), n, 2)
  y <- cumsum(e[,1])
  x <- cumsum(e[,2])
  dat <- cbind(y, x)

  r1 <- fjcoint(dat, test = "fourier")
  expect_equal(r1$test, "fourier")

  expect_error(fjcoint(dat, test = "johansen"), "urca")
})

test_that("print and plot do not error", {
  set.seed(42)
  n <- 200
  e <- matrix(rnorm(n * 2), n, 2)
  y <- cumsum(e[,1])
  x <- cumsum(e[,2])
  dat <- cbind(y = y, x = x)

  result <- fourier_test(dat, model = 1, k = 2, freq = 1)

  expect_output(print(result))
  expect_output(summary(result))
  expect_no_error(plot(result))
})