test_that("plotting works", {
    a <- adj(konigsberg$bridge_to, ids = konigsberg$area, duplicates = "allow")
    xy = cbind(konigsberg$x, konigsberg$y)
    expect_silent(plot(a))
    expect_silent(plot(a))
    expect_silent(plot(a, edges = "l"))
    expect_silent(plot(a, xy))
    expect_silent(plot(a, xy, edges = "s"))
    expect_silent(plot(a, xy, xlab = "Latitude", ylab = "Longitude"))
    expect_silent(plot(a, xy, xlab = NULL, ylab = NULL))
    expect_silent(plot(a, xy, nodes = FALSE))
    expect_silent(plot(adj(2, c(1, 3), 2)))
    expect_error(plot(adj(2, c(1, 3), 2), y = 5), "matrix")
})