skip_on_cran() # This test suite is long-running (on cran) and is skipped test_that("modifying theme element properties with + operator works", { # Changing a "leaf node" works t <- theme_grey() + theme(axis.title.x = element_text(colour = 'red', margin = margin())) expect_identical(t$axis.title.x, element_text(colour = 'red', margin = margin(), vjust = 1)) # Make sure the theme class didn't change or get dropped expect_true(is.theme(t)) # Make sure the element class didn't change or get dropped expect_true(inherits(t$axis.title.x, "element")) expect_true(inherits(t$axis.title.x, "element_text")) # Modifying an intermediate node works t <- theme_grey() + theme(axis.title = element_text(colour = 'red')) expect_identical(t$axis.title, element_text(colour = 'red')) # Modifying a root node changes only the specified properties t <- theme_grey() + theme(text = element_text(colour = 'red')) expect_identical(t$text$colour, 'red') expect_identical(t$text$family, theme_grey()$text$family) expect_identical(t$text$face, theme_grey()$text$face) expect_identical(t$text$size, theme_grey()$text$size) # Descendent is unchanged expect_identical(t$axis.title.x, theme_grey()$axis.title.x) # Adding element_blank replaces element t <- theme_grey() + theme(axis.text.y = element_blank()) expect_identical(t$axis.text.y, element_blank()) # Adding a non-blank element to an element_blank() replaces it t <- t + theme(axis.text.y = element_text(colour = 'red')) expect_identical(t$axis.text.y, element_text(colour = 'red')) # Adding empty theme() has no effect t <- theme_grey() + theme() expect_identical(t, theme_grey()) expect_error(theme_grey() + "asdf") }) test_that("adding theme object to ggplot object with + operator works", { ## test with complete theme p <- ggplot(data.frame(x = 1:3), aes(x, x)) + geom_point() + theme_grey() p <- p + theme(axis.title = element_text(size = 20)) expect_true(p$theme$axis.title$size == 20) # Should update specified properties, but not reset other properties p <- p + theme(text = element_text(colour = 'red')) expect_true(p$theme$text$colour == 'red') tt <- theme_grey()$text tt$colour <- 'red' expect_true(tt$inherit.blank) tt$inherit.blank <- FALSE expect_identical(p$theme$text, tt) ## test without complete theme p <- ggplot(data.frame(x = 1:3), aes(x, x)) + geom_point() p <- p + theme(axis.title = element_text(size = 20)) expect_true(p$theme$axis.title$size == 20) # Should update specified properties, but not reset other properties p <- p + theme(text = element_text(colour = 'red')) expect_true(p$theme$text$colour == 'red') expect_null(p$theme$text$family) expect_null(p$theme$text$face) expect_null(p$theme$text$size) expect_null(p$theme$text$hjust) expect_null(p$theme$text$vjust) expect_null(p$theme$text$angle) expect_null(p$theme$text$lineheight) expect_null(p$theme$text$margin) expect_null(p$theme$text$debug) ## stepwise addition of partial themes is identical to one-step addition p <- ggplot(data.frame(x = 1:3), aes(x, x)) + geom_point() p1 <- p + theme_light() + theme(axis.line.x = element_line(color = "blue")) + theme(axis.ticks.x = element_line(color = "red")) p2 <- p + theme_light() + theme(axis.line.x = element_line(color = "blue"), axis.ticks.x = element_line(color = "red")) expect_identical(p1$theme, p2$theme) }) test_that("replacing theme elements with %+replace% operator works", { # Changing a "leaf node" works t <- theme_grey() %+replace% theme(axis.title.x = element_text(colour = 'red')) expect_identical(t$axis.title.x, element_text(colour = 'red')) # Make sure the class didn't change or get dropped expect_true(is.theme(t)) # Changing an intermediate node works t <- theme_grey() %+replace% theme(axis.title = element_text(colour = 'red')) expect_identical(t$axis.title, element_text(colour = 'red')) # Descendent is unchanged expect_identical(t$axis.title.x, theme_grey()$axis.title.x) # Adding empty theme() has no effect t <- theme_grey() %+replace% theme() expect_identical(t, theme_grey()) expect_error(theme_grey() + "asdf") }) test_that("calculating theme element inheritance works", { t <- theme_grey() + theme(axis.title = element_text(colour = 'red')) # Check that properties are passed along from axis.title to axis.title.x e <- calc_element('axis.title.x', t) expect_identical(e$colour, 'red') expect_false(is.null(e$family)) expect_false(is.null(e$face)) expect_false(is.null(e$size)) # Check that rel() works for relative sizing, and is applied at each level t <- theme_grey(base_size = 12) + theme(axis.title = element_text(size = rel(0.5))) + theme(axis.title.x = element_text(size = rel(0.5))) e <- calc_element('axis.title', t) expect_identical(e$size, 6) ex <- calc_element('axis.title.x', t) expect_identical(ex$size, 3) # Check that a theme_blank in a parent node gets passed along to children t <- theme_grey() + theme(text = element_blank()) expect_identical(calc_element('axis.title.x', t), element_blank()) # Check that inheritance from derived class works element_dummyrect <- function(dummy) { # like element_rect but w/ dummy argument structure(list( fill = NULL, colour = NULL, dummy = dummy, linewidth = NULL, linetype = NULL, inherit.blank = FALSE ), class = c("element_dummyrect", "element_rect", "element")) } e <- calc_element( "panel.background", theme( rect = element_rect(fill = "white", colour = "black", linewidth = 0.5, linetype = 1), panel.background = element_dummyrect(dummy = 5), complete = TRUE # need to prevent pulling in default theme ) ) expect_identical( e, structure(list( fill = "white", colour = "black", dummy = 5, linewidth = 0.5, linetype = 1, inherit.blank = TRUE # this is true because we're requesting a complete theme ), class = c("element_dummyrect", "element_rect", "element")) ) # Check that blank elements are skipped in inheritance tree if and only if elements # don't inherit from blank. t <- theme_gray() + theme( strip.text = element_blank(), strip.text.x = element_text() # inherit.blank = FALSE is default ) e1 <- calc_element("strip.text.x", t) e2 <- calc_element("text", t) e2$inherit.blank <- FALSE # b/c inherit.blank = TRUE for complete themes expect_identical(e1, e2) theme <- theme_gray() + theme(strip.text = element_blank(), strip.text.x = element_text(inherit.blank = TRUE)) e1 <- ggplot2:::calc_element("strip.text.x", theme) e2 <- ggplot2:::calc_element("strip.text", theme) expect_identical(e1, e2) }) test_that("complete and non-complete themes interact correctly with each other", { # The 'complete' attribute of t1 + t2 is the OR of their 'complete' attributes. # But for _element properties_, the one on the right modifies the one on the left. t <- theme_bw() + theme(text = element_text(colour = 'red')) expect_true(attr(t, "complete")) expect_equal(t$text$colour, 'red') # A complete theme object (like theme_bw) always trumps a non-complete theme object t <- theme(text = element_text(colour = 'red')) + theme_bw() expect_true(attr(t, "complete")) expect_equal(t$text$colour, theme_bw()$text$colour) # Adding two non-complete themes: the one on the right modifies the one on the left. t <- theme(text = element_text(colour = 'blue')) + theme(text = element_text(colour = 'red')) expect_false(attr(t, "complete")) expect_equal(t$text$colour, 'red') }) test_that("complete and non-complete themes interact correctly with ggplot objects", { base <- ggplot(data.frame(x = 1:3), aes(x, x)) + geom_point() # Check that adding two theme successive theme objects to a ggplot object # works like adding the two theme object to each other p <- ggplot_build(base + theme_bw() + theme(text = element_text(colour = 'red'))) expect_true(attr(p$plot$theme, "complete")) # Compare the theme objects, after sorting the items, because item order can differ pt <- p$plot$theme tt <- theme_bw() + theme(text = element_text(colour = 'red')) pt <- pt[order(names(pt))] tt <- tt[order(names(tt))] expect_identical(pt, tt) p <- ggplot_build(base + theme(text = element_text(colour = 'red')) + theme_bw()) expect_true(attr(p$plot$theme, "complete")) # Compare the theme objects, after sorting the items, because item order can differ pt <- p$plot$theme tt <- theme(text = element_text(colour = 'red')) + theme_bw() pt <- pt[order(names(pt))] tt <- tt[order(names(tt))] expect_identical(pt, tt) p <- ggplot_build(base + theme(text = element_text(colour = 'red', face = 'italic'))) expect_false(attr(p$plot$theme, "complete")) expect_equal(p$plot$theme$text$colour, "red") expect_equal(p$plot$theme$text$face, "italic") p <- ggplot_build(base + theme(text = element_text(colour = 'red')) + theme(text = element_text(face = 'italic'))) expect_false(attr(p$plot$theme, "complete")) expect_equal(p$plot$theme$text$colour, "red") expect_equal(p$plot$theme$text$face, "italic") }) test_that("theme(validate=FALSE) means do not validate_element", { p <- ggplot(data.frame(x = 1:3), aes(x, x)) + geom_point() bw <- p + theme_bw() red.text <- theme(text = element_text(colour = "red")) bw.before <- bw + theme(animint.width = 500, validate = FALSE) expect_equal(bw.before$theme$animint.width, 500) bw.after <- p + theme(animint.width = 500, validate = FALSE) + theme_bw() expect_null(bw.after$theme$animint.width) red.after <- p + theme(animint.width = 500, validate = FALSE) + red.text expect_equal(red.after$theme$animint.width, 500) red.before <- p + red.text + theme(animint.width = 500, validate = FALSE) expect_equal(red.before$theme$animint.width, 500) }) test_that("theme validation happens at build stage", { # adding a non-valid theme element to a theme is no problem expect_silent(theme_gray() + theme(text = 0)) # the error occurs when we try to render the plot p <- ggplot() + theme(text = 0) expect_snapshot_error(print(p)) # without validation, the error occurs when the element is accessed p <- ggplot() + theme(text = 0, validate = FALSE) expect_snapshot_error(print(p)) }) test_that("incorrect theme specifications throw meaningful errors", { expect_snapshot_error(add_theme(theme_grey(), theme(line = element_rect()))) expect_snapshot_error(calc_element("line", theme(line = element_rect()))) register_theme_elements(element_tree = list(test = el_def("element_rect"))) expect_snapshot_error(calc_element("test", theme_gray() + theme(test = element_rect()))) }) test_that("element tree can be modified", { # we cannot add a new theme element without modifying the element tree p <- ggplot() + theme(blablabla = element_text(colour = "red")) expect_snapshot_error(print(p)) register_theme_elements( element_tree = list(blablabla = el_def("character", "text")) ) expect_snapshot_error(ggplotGrob(p)) register_theme_elements( element_tree = list(blablabla = el_def("unit", "text")) ) expect_snapshot_error(ggplotGrob(p)) # things work once we add a new element to the element tree register_theme_elements( element_tree = list(blablabla = el_def("element_text", "text")) ) expect_silent(ggplotGrob(p)) p1 <- ggplot() + theme(blablabla = element_line()) expect_snapshot_error(ggplotGrob(p1)) # inheritance and final calculation of novel element works final_theme <- ggplot2:::plot_theme(p, theme_gray()) e1 <- calc_element("blablabla", final_theme) e2 <- calc_element("text", final_theme) expect_identical(e1$family, e2$family) expect_identical(e1$face, e2$face) expect_identical(e1$size, e2$size) expect_identical(e1$lineheight, e2$lineheight) expect_identical(e1$colour, "red") # not inherited from element_text # existing elements can be overwritten ed <- el_def("element_rect", "rect") register_theme_elements( element_tree = list(axis.title = ed) ) expect_identical(get_element_tree()$axis.title, ed) reset_theme_settings(reset_current = FALSE) # revert back to defaults }) test_that("all elements in complete themes have inherit.blank=TRUE", { inherit_blanks <- function(theme) { all(vapply(theme, function(el) { if (inherits(el, "element") && !inherits(el, "element_blank")) { el$inherit.blank } else { TRUE } }, logical(1))) } expect_true(inherit_blanks(theme_grey())) expect_true(inherit_blanks(theme_bw())) expect_true(inherit_blanks(theme_classic())) expect_true(inherit_blanks(theme_dark())) expect_true(inherit_blanks(theme_light())) expect_true(inherit_blanks(theme_linedraw())) expect_true(inherit_blanks(theme_minimal())) expect_true(inherit_blanks(theme_void())) }) test_that("elements can be merged", { text_base <- element_text(colour = "red", size = 10) expect_equal( merge_element(element_text(colour = "blue"), text_base), element_text(colour = "blue", size = 10) ) rect_base <- element_rect(colour = "red", linewidth = 10) expect_equal( merge_element(element_rect(colour = "blue"), rect_base), element_rect(colour = "blue", linewidth = 10) ) line_base <- element_line(colour = "red", linewidth = 10) expect_equal( merge_element(element_line(colour = "blue"), line_base), element_line(colour = "blue", linewidth = 10) ) expect_error( merge_element(text_base, rect_base), "Only elements of the same class can be merged" ) }) test_that("theme elements that don't inherit from element can be combined", { expect_identical(combine_elements(1, NULL), 1) expect_identical(combine_elements(NULL, 1), 1) expect_identical(combine_elements(1, 0), 1) }) test_that("complete plot themes shouldn't inherit from default", { default_theme <- theme_gray() + theme(axis.text.x = element_text(colour = "red")) base <- ggplot(data.frame(x = 1), aes(x, x)) + geom_point() ptheme <- plot_theme(base + theme(axis.text.x = element_text(colour = "blue")), default_theme) expect_equal(ptheme$axis.text.x$colour, "blue") ptheme <- plot_theme(base + theme_void(), default_theme) expect_null(ptheme$axis.text.x) }) test_that("current theme can be updated with new elements", { old <- theme_set(theme_grey()) b1 <- ggplot() + theme_grey() b2 <- ggplot() # works for root element expect_identical( calc_element("text", plot_theme(b1)), calc_element("text", plot_theme(b2)) ) # works for derived element expect_identical( calc_element("axis.text.x", plot_theme(b1)), calc_element("axis.text.x", plot_theme(b2)) ) # theme calculation for nonexisting element returns NULL expect_identical(calc_element("abcde", plot_theme(b1)), NULL) # element tree gets merged properly register_theme_elements( abcde = element_text(color = "blue", hjust = 0, vjust = 1), element_tree = list(abcde = el_def("element_text", "text")) ) e1 <- calc_element("abcde", plot_theme(b2)) e2 <- calc_element("text", plot_theme(b2)) e2$colour <- "blue" e2$hjust <- 0 e2$vjust <- 1 expect_identical(e1, e2) reset_theme_settings() theme_set(old) }) test_that("titleGrob() and margins() work correctly", { # ascenders and descenders g1 <- titleGrob("aaaa", 0, 0, 0.5, 0.5) # lower-case letters, no ascenders or descenders g2 <- titleGrob("bbbb", 0, 0, 0.5, 0.5) # lower-case letters, no descenders g3 <- titleGrob("gggg", 0, 0, 0.5, 0.5) # lower-case letters, no ascenders g4 <- titleGrob("AAAA", 0, 0, 0.5, 0.5) # upper-case letters, no descenders expect_equal(height_cm(g1), height_cm(g2)) expect_equal(height_cm(g1), height_cm(g3)) expect_equal(height_cm(g1), height_cm(g4)) # margins g5 <- titleGrob("aaaa", 0, 0, 0.5, 0.5, margin = margin(t = 1, r = 0, b = 0, l = 0, unit = "cm"), margin_x = TRUE, margin_y = TRUE) g6 <- titleGrob("aaaa", 0, 0, 0.5, 0.5, margin = margin(t = 0, r = 1, b = 0, l = 0, unit = "cm"), margin_x = TRUE, margin_y = TRUE) g7 <- titleGrob("aaaa", 0, 0, 0.5, 0.5, margin = margin(t = 0, r = 0, b = 1, l = 0, unit = "cm"), margin_x = TRUE, margin_y = TRUE) g8 <- titleGrob("aaaa", 0, 0, 0.5, 0.5, margin = margin(t = 0, r = 0, b = 0, l = 1, unit = "cm"), margin_x = TRUE, margin_y = TRUE) expect_equal(height_cm(g5), height_cm(g1) + 1) expect_equal(width_cm(g5), width_cm(g1)) expect_equal(height_cm(g6), height_cm(g1)) expect_equal(width_cm(g6), width_cm(g1) + 1) expect_equal(height_cm(g7), height_cm(g1) + 1) expect_equal(width_cm(g7), width_cm(g1)) expect_equal(height_cm(g8), height_cm(g1)) expect_equal(width_cm(g8), width_cm(g1) + 1) # no margins when set to false g9 <- titleGrob("aaaa", 0, 0, 0.5, 0.5, margin = margin(t = 1, r = 1, b = 1, l = 1, unit = "cm"), margin_x = FALSE, margin_y = TRUE) g10 <- titleGrob("aaaa", 0, 0, 0.5, 0.5, margin = margin(t = 1, r = 1, b = 1, l = 1, unit = "cm"), margin_x = TRUE, margin_y = FALSE) expect_equal(height_cm(g9), height_cm(g1) + 2) # when one of margin_x or margin_y is set to FALSE and the other to TRUE, then the dimension for FALSE turns into # length 1null. expect_equal(g9$widths, grid::unit(1, "null")) expect_equal(g10$heights, grid::unit(1, "null")) expect_equal(width_cm(g10), width_cm(g1) + 2) }) test_that("provided themes explicitly define all elements", { elements <- names(.element_tree) t <- theme_all_null() expect_true(all(names(t) %in% elements)) expect_true(all(vapply(t, is.null, logical(1)))) t <- theme_grey() expect_true(all(names(t) %in% elements)) t <- theme_bw() expect_true(all(names(t) %in% elements)) t <- theme_linedraw() expect_true(all(names(t) %in% elements)) t <- theme_light() expect_true(all(names(t) %in% elements)) t <- theme_dark() expect_true(all(names(t) %in% elements)) t <- theme_minimal() expect_true(all(names(t) %in% elements)) t <- theme_classic() expect_true(all(names(t) %in% elements)) t <- theme_void() expect_true(all(names(t) %in% elements)) t <- theme_test() expect_true(all(names(t) %in% elements)) }) test_that("Theme elements are checked during build", { p <- ggplot(mtcars) + geom_point(aes(disp, mpg)) + theme(plot.title.position = "test") expect_snapshot_error(ggplotGrob(p)) p <- ggplot(mtcars) + geom_point(aes(disp, mpg)) + theme(plot.caption.position = "test") expect_snapshot_error(ggplotGrob(p)) p <- ggplot(mtcars) + geom_point(aes(disp, mpg)) + theme(plot.tag.position = "test") expect_snapshot_error(ggplotGrob(p)) }) # Visual tests ------------------------------------------------------------ test_that("aspect ratio is honored", { df <- cbind(data_frame(x = 1:8, y = 1:8, f = gl(2,4)), expand.grid(f1 = 1:2, f2 = 1:2, rep = 1:2)) p <- ggplot(df, aes(x, y)) + geom_point() + theme_test() + labs(x = NULL, y = NULL) p_a <- p + theme(aspect.ratio = 3) p_b <- p + theme(aspect.ratio = 1 / 3) expect_doppelganger("height is 3 times width", p_a ) expect_doppelganger("width is 3 times height", p_b ) expect_doppelganger("height is 3 times width, 2 wrap facets", p_a + facet_wrap(~f) ) expect_doppelganger("height is 3 times width, 2 column facets", p_a + facet_grid(.~f) ) expect_doppelganger("height is 3 times width, 2 row facets", p_a + facet_grid(f~.) ) expect_doppelganger("height is 3 times width, 2x2 facets", p_a + facet_grid(f1~f2) ) }) test_that("themes don't change without acknowledgement", { df <- data_frame(x = 1:3, y = 1:3, z = c("a", "b", "a"), a = 1) plot <- ggplot(df, aes(x, y, colour = z)) + geom_point() + facet_wrap(~ a) expect_doppelganger("theme_bw", plot + theme_bw()) expect_doppelganger("theme_classic", plot + theme_classic()) expect_doppelganger("theme_dark", plot + theme_dark()) expect_doppelganger("theme_minimal", plot + theme_minimal()) expect_doppelganger("theme_gray", plot + theme_gray()) expect_doppelganger("theme_light", plot + theme_light()) expect_doppelganger("theme_void", plot + theme_void()) expect_doppelganger("theme_linedraw", plot + theme_linedraw()) }) test_that("themes look decent at larger base sizes", { df <- data_frame(x = 1:3, y = 1:3, z = c("a", "b", "a"), a = 1) plot <- ggplot(df, aes(x, y, colour = z)) + geom_point() + facet_wrap(~ a) expect_doppelganger("theme_bw_large", plot + theme_bw(base_size = 33)) expect_doppelganger("theme_classic_large", plot + theme_classic(base_size = 33)) expect_doppelganger("theme_dark_large", plot + theme_dark(base_size = 33)) expect_doppelganger("theme_minimal_large", plot + theme_minimal(base_size = 33)) expect_doppelganger("theme_gray_large", plot + theme_gray(base_size = 33)) expect_doppelganger("theme_light_large", plot + theme_light(base_size = 33)) expect_doppelganger("theme_void_large", plot + theme_void(base_size = 33)) expect_doppelganger("theme_linedraw_large", plot + theme_linedraw(base_size = 33)) }) test_that("axes can be styled independently", { plot <- ggplot() + geom_point(aes(1:10, 1:10)) + scale_x_continuous(sec.axis = dup_axis()) + scale_y_continuous(sec.axis = dup_axis()) + theme( axis.title.x.top = element_text(colour = 'red'), axis.title.x.bottom = element_text(colour = 'green'), axis.title.y.left = element_text(colour = 'blue'), axis.title.y.right = element_text(colour = 'yellow'), axis.text.x.top = element_text(colour = 'red'), axis.text.x.bottom = element_text(colour = 'green'), axis.text.y.left = element_text(colour = 'blue'), axis.text.y.right = element_text(colour = 'yellow'), axis.ticks.x.top = element_line(colour = 'red'), axis.ticks.x.bottom = element_line(colour = 'green'), axis.ticks.y.left = element_line(colour = 'blue'), axis.ticks.y.right = element_line(colour = 'yellow'), axis.line.x.top = element_line(colour = 'red'), axis.line.x.bottom = element_line(colour = 'green'), axis.line.y.left = element_line(colour = 'blue'), axis.line.y.right = element_line(colour = 'yellow') ) expect_doppelganger("axes_styling", plot) }) test_that("axes ticks can have independent lengths", { plot <- ggplot() + theme_test() + geom_point(aes(1:10, 1:10)) + scale_x_continuous(sec.axis = dup_axis()) + scale_y_continuous(sec.axis = dup_axis()) + theme( axis.ticks.length.x.top = unit(-.5, "cm"), axis.ticks.length.x.bottom = unit(-.25, "cm"), axis.ticks.length.y.left = unit(.25, "cm"), axis.ticks.length.y.right = unit(.5, "cm"), axis.text.x.bottom = element_text(margin = margin(t = .25, unit = "cm")), axis.text.x.top = element_text(margin = margin(b = .25, unit = "cm")) ) expect_doppelganger("ticks_length", plot) }) test_that("strips can be styled independently", { df <- data_frame(x = 1:2, y = 1:2) plot <- ggplot(df, aes(x, y)) + facet_grid(x ~ y) + theme( strip.background.x = element_rect(fill = "red"), strip.background.y = element_rect(fill = "green") ) expect_doppelganger("strip_styling", plot) }) test_that("rotated axis tick labels work", { df <- data_frame( y = c(1, 2, 3), label = c("short", "medium size", "very long label") ) plot <- ggplot(df, aes(label, y)) + geom_point() + theme(axis.text.x = element_text(angle = 50, hjust = 1)) expect_doppelganger("rotated x axis tick labels", plot) }) test_that("plot titles and caption can be aligned to entire plot", { df <- data_frame( x = 1:3, y = 1:3, z = letters[1:3] ) plot <- ggplot(df, aes(x, y, color = z)) + geom_point() + facet_wrap(~z) + labs( title = "Plot title aligned to entire plot", subtitle = "Subtitle aligned to entire plot", caption = "Caption aligned to panels" ) + theme(plot.title.position = "plot") expect_doppelganger("titles aligned to entire plot", plot) plot <- ggplot(df, aes(x, y, color = z)) + geom_point() + facet_wrap(~z) + labs( title = "Plot title aligned to panels", subtitle = "Subtitle aligned to panels", caption = "Caption aligned to entire plot" ) + theme(plot.caption.position = "plot") expect_doppelganger("caption aligned to entire plot", plot) }) test_that("Strips can render custom elements", { element_test <- function(...) { el <- element_text(...) class(el) <- c('element_test', 'element_text', 'element') el } element_grob.element_test <- function(element, label = "", x = NULL, y = NULL, ...) { rectGrob(width = unit(1, "cm"), height = unit(1, "cm")) } df <- data_frame(x = 1:3, y = 1:3, a = letters[1:3]) plot <- ggplot(df, aes(x, y)) + geom_point() + facet_wrap(~a) + theme(strip.text = element_test()) expect_doppelganger("custom strip elements can render", plot) })