test_that("fuse twins behaves", {
  # Simple pedigree: two parents and two MZ twin children
  ped1 <- potter
  ped1$ID <- ped1$personID
  ped2 <- ped1
  ped2$famID <- 2

  ped2$ID <- ped2$personID + 100
  ped2$momID <- ped2$momID + 100
  ped2$dadID <- ped2$dadID + 100
  ped2$twinID <- ped2$twinID + 100

  ped <- rbind(ped1, ped2)
  remove(ped2)
  remove(ped1)
  #  returnRows = TRUE,
  # returnIDs = FALSE,
  # returnAsList = TRUE

  returnedRowsList <- findMZtwins(ped, returnRows = TRUE, returnIDs = FALSE, returnAsList = TRUE)
  returnIDsList <- findMZtwins(ped, returnRows = FALSE, returnIDs = TRUE, returnAsList = TRUE)
  returnedBothList <- findMZtwins(ped, returnRows = T, returnIDs = T, returnAsList = TRUE)

  # no error should be thrown when running fuseTwins with any of the above outputs as arguments
  expect_no_error(
    fuseTwins(ped,
      test_df_twins = TRUE,
      mz_id_pairs = NULL,
      mz_row_pairs = NULL
    )
  )

  expect_no_error(
    fuseTwins(ped,
      test_df_twins = TRUE,
      mz_id_pairs = NULL,
      mz_row_pairs = returnedRowsList
    )
  )
  expect_no_error(
    fuseTwins(ped,
      test_df_twins = TRUE,
      mz_id_pairs = returnIDsList,
      mz_row_pairs = NULL
    )
  )
  expect_no_error(
    fuseTwins(ped,
      test_df_twins = TRUE,
      mz_id_pairs = returnedBothList$pair_ids,
      mz_row_pairs = returnedBothList$pair_rows
    )
  )


  df_null <- tryCatch(
    fuseTwins(ped,
      test_df_twins = TRUE,
      mz_id_pairs = NULL,
      mz_row_pairs = NULL
    ),
    error = function(e) e
  )


  df_returnedRows <- tryCatch(
    fuseTwins(ped,
      test_df_twins = TRUE,
      mz_id_pairs = NULL,
      mz_row_pairs = returnedRowsList
    ),
    error = function(e) e
  )


  df_returnedIDs <- tryCatch(
    fuseTwins(ped,
      test_df_twins = TRUE,
      mz_id_pairs = returnIDsList,
      mz_row_pairs = NULL
    ),
    error = function(e) e
  )


  df_returnedBoth <- tryCatch(
    fuseTwins(ped,
      test_df_twins = TRUE,
      mz_id_pairs = returnedBothList$pair_ids,
      mz_row_pairs = returnedBothList$pair_rows
    ),
    error = function(e) e
  )


  expect_equal(df_returnedRows, df_returnedIDs)
  expect_equal(df_returnedRows, df_returnedBoth)
  expect_equal(df_returnedRows, df_null)
  expect_equal(nrow(df_returnedRows), 2) # One pair of twins should returned
})