test_that("f is nonzero if any solution is found", {
  I = 108
  J = 100
  K = 10
  df = array(rnorm(I*J*K), c(I,J,K))
  datasets = list(df, df)
  modes = list(c(1,2,3), c(1,4,5))
  Z = setupCMTFdata(datasets, modes)
  result = initializeACMTF(Z, 1, initialization="random")
  f = acmtf_fun(fac_to_vect(result), Z)
  expect_gt(f, 0)
})

test_that("an error is thrown for 4-way or more", {
  I = 108
  J = 100
  K = 10
  L = 5
  df = array(rnorm(I*J*K*L), c(I,J,K,L))
  datasets = list(df, df)
  modes = list(c(1,2,3,4), c(1,5,6,7))
  Z = setupCMTFdata(datasets, modes)
  result = initializeCMTF(Z, 1, initialization="random")

  expect_error(acmtf_fun(fac_to_vect(result), Z))
})