test_that("basic functions", {
  m <- matrix(
    c(
      0,
      0,
      0,
      0,
      0,
      0,
      0,
      1,
      0,
      0,
      0,
      1,
      2,
      1,
      0,
      0,
      0,
      1,
      0,
      0,
      0,
      0,
      0,
      0,
      0
    ),
    5,
    5,
    byrow = TRUE
  )

  l <- isolines((1:5) / 6, (5:1) / 6, m, c(.5, 1.5))

  # incorrect number of labels
  expect_snapshot(
    isolines_grob(l, labels = c("a", "b", "c")),
    error = TRUE
  )

  # incorrect margin specification
  expect_snapshot(
    isolines_grob(l, margin = 1:4),
    error = TRUE
  )
  expect_snapshot(
    isolines_grob(l, margin = grid::unit(1:3, "pt")),
    error = TRUE
  )

  # default settings create two labels per line for this dataset
  g <- isolines_grob(l, label_placer = label_placer_minmax(n = 0))
  expect_equal(g$labels_data$break_id, c("0.5", "0.5", "1.5", "1.5"))
  expect_equal(g$labels_data$label, c("0.5", "0.5", "1.5", "1.5"))
  expect_equal(g$labels_data$x, rep(0.5, 4))
  expect_equal(g$labels_data$theta, rep(0, 4))
  expect_true(all(
    abs(g$labels_data$y - c(0.75, 0.25, 0.5833333, 0.4166667)) < 1e-7
  ))

  # extra breaks are ignored
  g <- isolines_grob(
    l,
    breaks = c("0.5", "1.5", "2.5"),
    labels = c("a", "b", "c")
  )
  expect_equal(g$labels_data$break_id, c("0.5", "0.5", "1.5", "1.5"))
  expect_equal(g$labels_data$label, c("a", "a", "b", "b"))
})