context("Local updating")
library("anticlust")

test_that("local updating works correctly for k-means anticlustering", {
  
  M <- 2
  N <- 60
  K <- 2
  clusters <- sample(rep(1:K, c(40, 20)))
  features <- matrix(rnorm(N * M), ncol = M)

  # Swap two items and check objective
  to_swap <- sample(1:K, size = 2)
  swap1 <- which(clusters == to_swap[1])[1]
  swap2 <- which(clusters == to_swap[2])[1]
  
  centers <- cluster_centers(features, clusters)
  
  # Compute clusters after swap
  local_update_centers <- update_centers(
    centers, 
    features, 
    swap1, 
    swap2, 
    clusters[swap1], 
    clusters[swap2], 
    table(clusters)
  )
  
  # swap clusters, and recompute cluster centers
  tmp <- clusters[swap1]
  clusters[swap1] <- clusters[swap2]
  clusters[swap2] <- tmp
  
  centers_after_swap <- cluster_centers(features, clusters)
  
  expect_equal(local_update_centers, centers_after_swap)
  
})