context("cv")
test_that("Each person one Fold", {
  theFolds <- createLeavePersonsOutFolds(lgcm)
  ids <- getData(lgcm)[, gppm:::getID(getData(lgcm))]
  uIds <- sort(unique(ids))
  folds <- vector(mode = "integer", length(uIds))
  for (i in 1:length(ids)) {
    idIdx <- uIds == ids[i]
    if (folds[idIdx] == 0) {
      folds[idIdx] <- theFolds[i]
    } else {
      expect_identical(folds[idIdx], theFolds[i])
    }
  }
})


test_that("Folds roughly same size", {
  theFolds <- createLeavePersonsOutFolds(lgcm)
  proportion <- table(theFolds) / sum(table(theFolds))
  expect(all(proportion > 0.09 & proportion < 0.11), "Folds are not roughly equal")
})


test_that("full cv", {
  skip_on_cran()
  theT <- rnorm(10000)
  theY <- theT + rnorm(10000)
  fakeData <- data.frame(ID = rep(1:2500, 4), t = theT, y = theY)
  linearReg <- gppm("b*t", "noise*(t==t#)", fakeData, ID = "ID", DV = "y")
  theFolds <- createLeavePersonsOutFolds(linearReg, k = 2)
  cvRes <- crossvalidate(linearReg, theFolds)
  expect_equal(cvRes$MSE / 2, .5, tolerance = 0.02)
  sum <- 0
  for (i in 1:10000) {
    sum <- sum + log(dnorm(rnorm(1)))
  }
  sum <- -sum
  expect_equal(cvRes$nLPP / 10000, sum / 10000, tolerance = 0.05)
})