d <- data.frame(x = 3, y = 4) p <- ggplot(d, aes(x, y)) test_that("default settings yield multiple isolines", { p1 <- p + geom_isoline() # only one row l1 <- layer_data(p1) expect_equal(nrow(l1), 1L) # several lines g1 <- layer_grob(p1) expect_true(length(g1[[1L]]$children[[1L]]) > 2) }) # TODO: Test that endpoints lie outside plotting window.