diff --git a/NAMESPACE b/NAMESPACE
index 96959a985a..00c46a0bf0 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -458,6 +458,21 @@ export(is.facet)
 export(is.ggplot)
 export(is.ggproto)
 export(is.theme)
+export(is_coord)
+export(is_element)
+export(is_facet)
+export(is_geom)
+export(is_ggplot)
+export(is_ggproto)
+export(is_guide)
+export(is_guides)
+export(is_layer)
+export(is_mapping)
+export(is_margin)
+export(is_position)
+export(is_scale)
+export(is_stat)
+export(is_theme)
 export(label_both)
 export(label_bquote)
 export(label_context)
diff --git a/NEWS.md b/NEWS.md
index a5988574f8..f139b4e263 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,9 @@
 # ggplot2 (development version)
 
+* Standardised test functions for important classes: `is_ggproto()`, 
+ `is_ggplot()`, `is_mapping()`, `is_layer()`, `is_geom()`, `is_stat()`, 
+ `is_position()`, `is_coord()`, `is_facet()`, `is_scale()`, `is_guide()`, 
+ `is_guides()`, `is_margin()`, `is_element()` and `is_theme()`.
 * New `get_labs()` function for retrieving completed plot labels 
   (@teunbrand, #6008).
 * New `get_geom_defaults()` for retrieving resolved default aesthetics.
diff --git a/R/aes.R b/R/aes.R
index 4120657222..483cd85bad 100644
--- a/R/aes.R
+++ b/R/aes.R
@@ -102,6 +102,10 @@ aes <- function(x, y, ...) {
   rename_aes(aes)
 }
 
+#' @export
+#' @rdname is_tests
+is_mapping <- function(x) inherits(x, "uneval")
+
 # Wrap symbolic objects in quosures but pull out constants out of
 # quosures for backward-compatibility
 new_aesthetic <- function(x, env = globalenv()) {
diff --git a/R/coord-.R b/R/coord-.R
index dc7090c352..0f2c0f3ca2 100644
--- a/R/coord-.R
+++ b/R/coord-.R
@@ -204,11 +204,17 @@ Coord <- ggproto("Coord",
   }
 )
 
-#' Is this object a coordinate system?
-#'
-#' @export is.Coord
-#' @keywords internal
-is.Coord <- function(x) inherits(x, "Coord")
+#' @export
+#' @rdname is_tests
+is_coord <- function(x) inheritS(x, "Coord")
+
+#' @export
+#' @rdname is_tests
+#' @usage is.Coord(x) # Deprecated
+is.Coord <- function(x) {
+  deprecate_soft0("3.5.2", "is.Coord()", "is_coord()")
+  is_coord(x)
+}
 
 # Renders an axis with the correct orientation or zeroGrob if no axis should be
 # generated
diff --git a/R/coord-cartesian-.R b/R/coord-cartesian-.R
index 74f46433db..35be78a285 100644
--- a/R/coord-cartesian-.R
+++ b/R/coord-cartesian-.R
@@ -159,7 +159,7 @@ view_scales_from_scale <- function(scale, coord_limits = NULL, expand = TRUE) {
 }
 
 panel_guides_grob <- function(guides, position, theme, labels = NULL) {
-  if (!inherits(guides, "Guides")) {
+  if (!is_guides(guides)) {
     return(zeroGrob())
   }
   pair <- guides$get_position(position)
diff --git a/R/facet-.R b/R/facet-.R
index abdd373d05..533d8a2eaf 100644
--- a/R/facet-.R
+++ b/R/facet-.R
@@ -239,13 +239,17 @@ vars <- function(...) {
   quos(...)
 }
 
+#' @export
+#' @rdname is_tests
+is_facet <- function(x) inherits(x, "Facet")
 
-#' Is this object a faceting specification?
-#'
-#' @param x object to test
-#' @keywords internal
 #' @export
-is.facet <- function(x) inherits(x, "Facet")
+#' @rdname is_tests
+#' @usage is.facet(x) # Deprecated
+is.facet <- function(x) {
+  deprecate_soft0("3.5.2", "is.facet()", "is_facet()")
+  is_facet(x)
+}
 
 # A "special" value, currently not used but could be used to determine
 # if faceting is active
@@ -324,7 +328,7 @@ as_facets_list <- function(x) {
 }
 
 validate_facets <- function(x) {
-  if (inherits(x, "uneval")) {
+  if (is_mapping(x)) {
     cli::cli_abort("Please use {.fn vars} to supply facet variables.")
   }
   # Native pipe have higher precedence than + so any type of gg object can be
diff --git a/R/fortify.R b/R/fortify.R
index b9cf025f2a..15d61c3fd0 100644
--- a/R/fortify.R
+++ b/R/fortify.R
@@ -82,7 +82,7 @@ fortify.default <- function(model, data, ...) {
     "or an object coercible by {{.fn fortify}}, or a valid ",
     "{{.cls data.frame}}-like object coercible by {{.fn as.data.frame}}"
   )
-  if (inherits(model, "uneval")) {
+  if (is_mapping(model)) {
     msg <- c(
       glue(msg0, ", not {obj_type_friendly(model)}."),
       "i" = "Did you accidentally pass {.fn aes} to the {.arg data} argument?"
diff --git a/R/geom-.R b/R/geom-.R
index c1967a89c1..6ad6fb67fb 100644
--- a/R/geom-.R
+++ b/R/geom-.R
@@ -222,6 +222,9 @@ Geom <- ggproto("Geom",
 
 )
 
+#' @export
+#' @rdname is_tests
+is_geom <- function(x) inherits(x, "Geom")
 
 #' Graphical units
 #'
diff --git a/R/ggproto.R b/R/ggproto.R
index 48b1fcf96f..d7225dd7a7 100644
--- a/R/ggproto.R
+++ b/R/ggproto.R
@@ -52,7 +52,7 @@
 #'     self$x
 #'   }
 #'  )
-#' is.ggproto(Adder)
+#' is_ggproto(Adder)
 #'
 #' Adder$add(10)
 #' Adder$add(10)
@@ -88,7 +88,7 @@ ggproto <- function(`_class` = NULL, `_inherit` = NULL, ...) {
 
   super <- find_super()
   if (!is.null(super)) {
-    check_object(super, is.ggproto, "a {.cls ggproto} object", arg = "_inherit")
+    check_object(super, is_ggproto, "a {.cls ggproto} object", arg = "_inherit")
     e$super <- find_super
     class(e) <- c(`_class`, class(super))
   } else {
@@ -106,10 +106,17 @@ ggproto_parent <- function(parent, self) {
   structure(list(parent = parent, self = self), class = "ggproto_parent")
 }
 
-#' @param x An object to test.
 #' @export
-#' @rdname ggproto
-is.ggproto <- function(x) inherits(x, "ggproto")
+#' @rdname is_tests
+is_ggproto <- function(x) inherits(x, "ggproto")
+
+#' @export
+#' @rdname is_tests
+#' @usage is.ggproto(x) # Deprecated
+is.ggproto <- function(x) {
+  deprecate_soft0("3.5.2", "is.ggproto()", "is_ggproto()")
+  is_ggproto(x)
+}
 
 fetch_ggproto <- function(x, name) {
   res <- NULL
@@ -305,7 +312,7 @@ object_summaries <- function(x, exclude = NULL, flat = TRUE) {
   values <- vapply(obj_names, function(name) {
     obj <- x[[name]]
     if (is.function(obj)) "function"
-    else if (is.ggproto(obj)) format(obj, flat = flat)
+    else if (is_ggproto(obj)) format(obj, flat = flat)
     else if (is.environment(obj)) "environment"
     else if (is.null(obj)) "NULL"
     else if (is.atomic(obj)) trim(paste(as.character(obj), collapse = " "))
diff --git a/R/guide-.R b/R/guide-.R
index 0a334c4580..1d31ddc957 100644
--- a/R/guide-.R
+++ b/R/guide-.R
@@ -50,7 +50,7 @@ new_guide <- function(..., available_aes = "any", super) {
 
   # Validate theme settings
   if (!is.null(params$theme)) {
-    check_object(params$theme, is.theme, what = "a {.cls theme} object")
+    check_object(params$theme, is_theme, what = "a {.cls theme} object")
     validate_theme(params$theme, call = caller_env())
     params$direction <- params$direction %||% params$theme$legend.direction
   }
@@ -66,6 +66,10 @@ new_guide <- function(..., available_aes = "any", super) {
   )
 }
 
+#' @export
+#' @rdname is_tests
+is_guide <- function(x) inherits(x, "Guide")
+
 #' @section Guides:
 #'
 #' The `guide_*()` functions, such as `guide_legend()` return an object that
@@ -377,10 +381,10 @@ Guide <- ggproto(
   # Renders tickmarks
   build_ticks = function(key, elements, params, position = params$position,
                          length = elements$ticks_length) {
-    if (!inherits(elements, "element")) {
+    if (!is_element(elements)) {
       elements <- elements$ticks
     }
-    if (!inherits(elements, "element_line")) {
+    if (!is_element(elements, "line")) {
       return(zeroGrob())
     }
 
diff --git a/R/guide-axis.R b/R/guide-axis.R
index 22cda82454..221c2de2ce 100644
--- a/R/guide-axis.R
+++ b/R/guide-axis.R
@@ -240,7 +240,7 @@ GuideAxis <- ggproto(
 
   override_elements = function(params, elements, theme) {
     label <- elements$text
-    if (!inherits(label, "element_text")) {
+    if (!is_element(label, "text")) {
       return(elements)
     }
     label_overrides <- axis_label_element_overrides(
diff --git a/R/guide-legend.R b/R/guide-legend.R
index ecf47b3089..6581c31556 100644
--- a/R/guide-legend.R
+++ b/R/guide-legend.R
@@ -787,7 +787,7 @@ deprecated_guide_args <- function(
 
   # Set as theme
   theme <- compact(theme)
-  if (!is.theme(theme)) {
+  if (!is_theme(theme)) {
     theme <- inject(theme(!!!theme))
   }
   theme
diff --git a/R/guides-.R b/R/guides-.R
index 3ad66a4bf5..bd91989216 100644
--- a/R/guides-.R
+++ b/R/guides-.R
@@ -109,9 +109,13 @@ guides <- function(...) {
   NULL
 }
 
+#' @export
+#' @rdname is_tests
+is_guides <- function(x) inherits(x, "Guides")
+
 update_guides <- function(p, guides) {
   p <- plot_clone(p)
-  if (inherits(p$guides, "Guides")) {
+  if (is_guides(p$guides)) {
     old <- p$guides
     new <- ggproto(NULL, old)
     new$add(guides)
@@ -151,7 +155,7 @@ Guides <- ggproto(
     if (is.null(guides)) {
       return(invisible())
     }
-    if (inherits(guides, "Guides")) {
+    if (is_guides(guides)) {
       guides <- guides$guides
     }
     self$guides <- defaults(guides, self$guides)
@@ -898,7 +902,7 @@ validate_guide <- function(guide) {
       guide <- fun()
     }
   }
-  if (inherits(guide, "Guide")) {
+  if (is_guide(guide)) {
     return(guide)
   }
   if (inherits(guide, "guide") && is.list(guide)) {
diff --git a/R/layer.R b/R/layer.R
index 7df5119aae..5bd949a4ed 100644
--- a/R/layer.R
+++ b/R/layer.R
@@ -199,7 +199,7 @@ layer <- function(geom = NULL, stat = NULL,
 }
 
 validate_mapping <- function(mapping, call = caller_env()) {
-  if (!inherits(mapping, "uneval")) {
+  if (!is_mapping(mapping)) {
     msg <- "{.arg mapping} must be created by {.fn aes}."
     # Native pipe have higher precedence than + so any type of gg object can be
     # expected here, not just ggplot
@@ -462,7 +462,9 @@ Layer <- ggproto("Layer", NULL,
   }
 )
 
-is.layer <- function(x) inherits(x, "Layer")
+#' @export
+#' @rdname is_tests
+is_layer <- function(x) inherits(x, "Layer")
 
 check_subclass <- function(x, subclass,
                            argname = to_lower_ascii(subclass),
diff --git a/R/margins.R b/R/margins.R
index b563331002..6e3b1319ac 100644
--- a/R/margins.R
+++ b/R/margins.R
@@ -8,7 +8,10 @@ margin <- function(t = 0, r = 0, b = 0, l = 0, unit = "pt") {
   class(u) <- c("margin", class(u))
   u
 }
-is.margin <- function(x) {
+
+#' @export
+#' @rdname is_tests
+is_margin <- function(x) {
   inherits(x, "margin")
 }
 
diff --git a/R/plot-build.R b/R/plot-build.R
index 291841de90..de38e02675 100644
--- a/R/plot-build.R
+++ b/R/plot-build.R
@@ -272,7 +272,7 @@ ggplot_gtable.ggplot_built <- function(data) {
   plot_table <- gtable_add_rows(plot_table, theme$plot.margin[3])
   plot_table <- gtable_add_cols(plot_table, theme$plot.margin[4], pos = 0)
 
-  if (inherits(theme$plot.background, "element")) {
+  if (is_element(theme$plot.background)) {
     plot_table <- gtable_add_grob(plot_table,
       element_render(theme, "plot.background"),
       t = 1, l = 1, b = -1, r = -1, name = "background", z = -Inf)
diff --git a/R/plot-construction.R b/R/plot-construction.R
index b6d83fe1f0..535b2e9563 100644
--- a/R/plot-construction.R
+++ b/R/plot-construction.R
@@ -51,9 +51,9 @@
   # can be displayed in error messages
   e2name <- deparse(substitute(e2))
 
-  if      (is.theme(e1))  add_theme(e1, e2, e2name)
-  else if (is.ggplot(e1)) add_ggplot(e1, e2, e2name)
-  else if (is.ggproto(e1)) {
+  if      (is_theme(e1))  add_theme(e1, e2, e2name)
+  else if (is_ggplot(e1)) add_ggplot(e1, e2, e2name)
+  else if (is_ggproto(e1)) {
     cli::cli_abort(c(
       "Cannot add {.cls ggproto} objects together.",
       "i" = "Did you forget to add this object to a {.cls ggplot} object?"
diff --git a/R/plot.R b/R/plot.R
index 0d1df80f98..b7d0dff6f4 100644
--- a/R/plot.R
+++ b/R/plot.R
@@ -111,7 +111,7 @@ ggplot <- function(data = NULL, mapping = aes(), ...,
 #' @export
 ggplot.default <- function(data = NULL, mapping = aes(), ...,
                            environment = parent.frame()) {
-  if (!missing(mapping) && !inherits(mapping, "uneval")) {
+  if (!missing(mapping) && !is_mapping(mapping)) {
     cli::cli_abort(c(
       "{.arg mapping} must be created with {.fn aes}.",
       "x" = "You've supplied {.obj_type_friendly {mapping}}."
@@ -156,11 +156,20 @@ plot_clone <- function(plot) {
   p
 }
 
-#' Reports whether x is a ggplot object
+#' Reports wether `x` is a type of object
 #' @param x An object to test
 #' @keywords internal
 #' @export
-is.ggplot <- function(x) inherits(x, "ggplot")
+#' @name is_tests
+is_ggplot <- function(x) inherits(x, "ggplot")
+
+#' @export
+#' @rdname is_tests
+#' @usage is.ggplot(x) # Deprecated
+is.ggplot <- function(x) {
+  deprecate_soft0("3.5.2", "is.ggplot", "is_ggplot")
+  is_ggplot(x)
+}
 
 #' Explicitly draw plot
 #'
diff --git a/R/position-.R b/R/position-.R
index 559c6c68d0..c731f2b3cc 100644
--- a/R/position-.R
+++ b/R/position-.R
@@ -69,6 +69,10 @@ Position <- ggproto("Position",
   }
 )
 
+#' @export
+#' @rdname is_tests
+is_position <- function(x) inherits(x, "Position")
+
 #' Convenience function to transform all position variables.
 #'
 #' @param trans_x,trans_y Transformation functions for x and y aesthetics.
diff --git a/R/scale-.R b/R/scale-.R
index 0b374d72ef..15c8ea1d5b 100644
--- a/R/scale-.R
+++ b/R/scale-.R
@@ -350,6 +350,10 @@ binned_scale <- function(aesthetics, scale_name = deprecated(), palette, name =
   )
 }
 
+#' @export
+#' @rdname is_tests
+is_scale <- function(x) inherits(x, "Scale")
+
 #' @section Scales:
 #'
 #' All `scale_*` functions like [scale_x_continuous()] return a `Scale*`
diff --git a/R/scale-colour.R b/R/scale-colour.R
index 71255e2033..47f14063c3 100644
--- a/R/scale-colour.R
+++ b/R/scale-colour.R
@@ -197,7 +197,7 @@ scale_fill_binned <- function(...,
 # helper function to make sure that the provided scale is of the correct
 # type (i.e., is continuous and works with the provided aesthetic)
 check_scale_type <- function(scale, name, aesthetic, scale_is_discrete = FALSE, call = caller_env()) {
-  if (!is.ggproto(scale) || !inherits(scale, "Scale")) {
+  if (!is_ggproto(scale) || !is_scale(scale)) {
     cli::cli_abort(c(
       "The {.arg type} argument must return a continuous scale for the {.field {aesthetic}} aesthetic.",
       "x" = "The provided object is not a scale function."
diff --git a/R/stat-.R b/R/stat-.R
index 2d56937b06..186341eb78 100644
--- a/R/stat-.R
+++ b/R/stat-.R
@@ -218,3 +218,7 @@ Stat <- ggproto("Stat",
   }
 
 )
+
+#' @export
+#' @rdname is_tests
+is_stat <- function(x) inherits(x, "Stat")
diff --git a/R/theme-current.R b/R/theme-current.R
index b56b2e1651..839a02371d 100644
--- a/R/theme-current.R
+++ b/R/theme-current.R
@@ -90,7 +90,7 @@ theme_get <- function() {
 #' @param new new theme (a list of theme elements)
 #' @export
 theme_set <- function(new) {
-  check_object(new, is.theme, "a {.cls theme} object")
+  check_object(new, is_theme, "a {.cls theme} object")
   old <- ggplot_global$theme_current
   ggplot_global$theme_current <- new
   invisible(old)
@@ -111,7 +111,7 @@ theme_replace <- function(...) {
 #' @rdname theme_get
 #' @export
 "%+replace%" <- function(e1, e2) {
-  if (!is.theme(e1) || !is.theme(e2)) {
+  if (!is_theme(e1) || !is_theme(e2)) {
     cli::cli_abort("{.code %+replace%} requires two theme objects")
   }
 
diff --git a/R/theme-elements.R b/R/theme-elements.R
index b8e83c75e4..35ac8624f3 100644
--- a/R/theme-elements.R
+++ b/R/theme-elements.R
@@ -21,6 +21,8 @@
 #'   a blank element among its parents will cause this element to be blank as
 #'   well. If `FALSE` any blank parent element will be ignored when
 #'   calculating final element state.
+#' @param type For testing elements: the type of element to expect. One of
+#'   `"blank"`, `"rect"`, `"line"` or `"text"`.
 #' @return An S3 object of class `element`, `rel`, or `margin`.
 #' @examples
 #' plot <- ggplot(mpg, aes(displ, hwy)) + geom_point()
@@ -144,6 +146,22 @@ element_text <- function(family = NULL, face = NULL, colour = NULL,
   )
 }
 
+#' @export
+#' @rdname element
+is_element <- function(x, type = "any") {
+  switch(
+    type %||% "any",
+    any   = inherits(x, "element"),
+    rect  = inherits(x, "element_rect"),
+    line  = inherits(x, "element_line"),
+    text  = inherits(x, "element_text"),
+    blank = inherits(x, "element_blank"),
+    # TODO: ideally we accept more elements from extensions. We need to
+    # consider how this will work with S7 classes, where ggplot2 doesn't know
+    # about the extension's class objects.
+    FALSE
+  )
+}
 
 #' @export
 print.element <- function(x, ...) utils::str(x)
diff --git a/R/theme.R b/R/theme.R
index 3611af323e..e7bb9c0994 100644
--- a/R/theme.R
+++ b/R/theme.R
@@ -475,7 +475,7 @@ theme <- function(...,
     elements$panel.spacing.y <- elements$panel.margin.y
     elements$panel.margin.y <- NULL
   }
-  if (is.unit(elements$legend.margin) && !is.margin(elements$legend.margin)) {
+  if (is.unit(elements$legend.margin) && !is_margin(elements$legend.margin)) {
     cli::cli_warn(c(
       "{.var legend.margin} must be specified using {.fn margin}",
       "i" = "For the old behavior use {.var legend.spacing}"
@@ -521,7 +521,7 @@ theme <- function(...,
   # If complete theme set all non-blank elements to inherit from blanks
   if (complete) {
     elements <- lapply(elements, function(el) {
-      if (inherits(el, "element") && !inherits(el, "element_blank")) {
+      if (is_element(el) && !is_element(el, "blank")) {
         el$inherit.blank <- TRUE
       }
       el
@@ -821,7 +821,7 @@ combine_elements <- function(e1, e2) {
   }
 
   # If neither of e1 or e2 are element_* objects, return e1
-  if (!inherits(e1, "element") && !inherits(e2, "element")) {
+  if (!is_element(e1) && !is_element(e2)) {
     return(e1)
   }
 
@@ -864,11 +864,18 @@ is.subclass <- function(x, y) {
   !any(inheritance == 0) && length(setdiff(class(x), class(y))) > 0
 }
 
-#' Reports whether x is a theme object
-#' @param x An object to test
+
 #' @export
-#' @keywords internal
-is.theme <- function(x) inherits(x, "theme")
+#' @rdname is_tests
+is_theme <- function(x) inherits(x, "theme")
+
+#' @export
+#' @rdname is_tests
+#' @usage is.theme(x) # Deprecated
+is.theme <- function(x) {
+  deprecate_soft0("3.5.2", "is.theme", "is_theme")
+  is_theme(x)
+}
 
 #' @export
 `$.theme` <- function(x, ...) {
diff --git a/man/element.Rd b/man/element.Rd
index a3c27a259c..b76ccf0b50 100644
--- a/man/element.Rd
+++ b/man/element.Rd
@@ -5,6 +5,7 @@
 \alias{element_rect}
 \alias{element_line}
 \alias{element_text}
+\alias{is_element}
 \alias{rel}
 \alias{margin}
 \title{Theme elements}
@@ -47,6 +48,8 @@ element_text(
   inherit.blank = FALSE
 )
 
+is_element(x, type = "any")
+
 rel(x)
 
 margin(t = 0, r = 0, b = 0, l = 0, unit = "pt")
@@ -97,6 +100,9 @@ is anchored.}
 
 \item{x}{A single number specifying size relative to parent element.}
 
+\item{type}{For testing elements: the type of element to expect. One of
+\code{"blank"}, \code{"rect"}, \code{"line"} or \code{"text"}.}
+
 \item{t, r, b, l}{Dimensions of each margin. (To remember order, think trouble).}
 
 \item{unit}{Default units of dimensions. Defaults to "pt" so it
diff --git a/man/ggproto.Rd b/man/ggproto.Rd
index c00c2000f6..faeb7d70e2 100644
--- a/man/ggproto.Rd
+++ b/man/ggproto.Rd
@@ -3,14 +3,11 @@
 \name{ggproto}
 \alias{ggproto}
 \alias{ggproto_parent}
-\alias{is.ggproto}
 \title{Create a new ggproto object}
 \usage{
 ggproto(`_class` = NULL, `_inherit` = NULL, ...)
 
 ggproto_parent(parent, self)
-
-is.ggproto(x)
 }
 \arguments{
 \item{_class}{Class name to assign to the object. This is stored as the class
@@ -24,8 +21,6 @@ inherit from any object.}
 functions that become methods of the class or regular objects.}
 
 \item{parent, self}{Access parent class \code{parent} of object \code{self}.}
-
-\item{x}{An object to test.}
 }
 \description{
 Construct a new object with \code{ggproto()}, test with \code{is.ggproto()},
@@ -77,7 +72,7 @@ Adder <- ggproto("Adder",
     self$x
   }
  )
-is.ggproto(Adder)
+is_ggproto(Adder)
 
 Adder$add(10)
 Adder$add(10)
diff --git a/man/is.Coord.Rd b/man/is.Coord.Rd
deleted file mode 100644
index 50b4520640..0000000000
--- a/man/is.Coord.Rd
+++ /dev/null
@@ -1,12 +0,0 @@
-% Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/coord-.R
-\name{is.Coord}
-\alias{is.Coord}
-\title{Is this object a coordinate system?}
-\usage{
-is.Coord(x)
-}
-\description{
-Is this object a coordinate system?
-}
-\keyword{internal}
diff --git a/man/is.facet.Rd b/man/is.facet.Rd
deleted file mode 100644
index bd8fc7b5ba..0000000000
--- a/man/is.facet.Rd
+++ /dev/null
@@ -1,15 +0,0 @@
-% Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/facet-.R
-\name{is.facet}
-\alias{is.facet}
-\title{Is this object a faceting specification?}
-\usage{
-is.facet(x)
-}
-\arguments{
-\item{x}{object to test}
-}
-\description{
-Is this object a faceting specification?
-}
-\keyword{internal}
diff --git a/man/is.ggplot.Rd b/man/is.ggplot.Rd
deleted file mode 100644
index 837bc9a919..0000000000
--- a/man/is.ggplot.Rd
+++ /dev/null
@@ -1,15 +0,0 @@
-% Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/plot.R
-\name{is.ggplot}
-\alias{is.ggplot}
-\title{Reports whether x is a ggplot object}
-\usage{
-is.ggplot(x)
-}
-\arguments{
-\item{x}{An object to test}
-}
-\description{
-Reports whether x is a ggplot object
-}
-\keyword{internal}
diff --git a/man/is.theme.Rd b/man/is.theme.Rd
deleted file mode 100644
index c7930a2e96..0000000000
--- a/man/is.theme.Rd
+++ /dev/null
@@ -1,15 +0,0 @@
-% Generated by roxygen2: do not edit by hand
-% Please edit documentation in R/theme.R
-\name{is.theme}
-\alias{is.theme}
-\title{Reports whether x is a theme object}
-\usage{
-is.theme(x)
-}
-\arguments{
-\item{x}{An object to test}
-}
-\description{
-Reports whether x is a theme object
-}
-\keyword{internal}
diff --git a/man/is_tests.Rd b/man/is_tests.Rd
new file mode 100644
index 0000000000..d6846f1ca8
--- /dev/null
+++ b/man/is_tests.Rd
@@ -0,0 +1,72 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/ggproto.R, R/aes.R, R/geom-.R, R/coord-.R,
+%   R/facet-.R, R/stat-.R, R/guide-.R, R/layer.R, R/guides-.R, R/margins.R,
+%   R/plot.R, R/position-.R, R/scale-.R, R/theme.R
+\name{is_ggproto}
+\alias{is_ggproto}
+\alias{is.ggproto}
+\alias{is_mapping}
+\alias{is_geom}
+\alias{is_coord}
+\alias{is.Coord}
+\alias{is_facet}
+\alias{is.facet}
+\alias{is_stat}
+\alias{is_guide}
+\alias{is_layer}
+\alias{is_guides}
+\alias{is_margin}
+\alias{is_tests}
+\alias{is_ggplot}
+\alias{is.ggplot}
+\alias{is_position}
+\alias{is_scale}
+\alias{is_theme}
+\alias{is.theme}
+\title{Reports wether \code{x} is a type of object}
+\usage{
+is_ggproto(x)
+
+is.ggproto(x) # Deprecated
+
+is_mapping(x)
+
+is_geom(x)
+
+is_coord(x)
+
+is.Coord(x) # Deprecated
+
+is_facet(x)
+
+is.facet(x) # Deprecated
+
+is_stat(x)
+
+is_guide(x)
+
+is_layer(x)
+
+is_guides(x)
+
+is_margin(x)
+
+is_ggplot(x)
+
+is.ggplot(x) # Deprecated
+
+is_position(x)
+
+is_scale(x)
+
+is_theme(x)
+
+is.theme(x) # Deprecated
+}
+\arguments{
+\item{x}{An object to test}
+}
+\description{
+Reports wether \code{x} is a type of object
+}
+\keyword{internal}
diff --git a/tests/testthat/test-function-args.R b/tests/testthat/test-function-args.R
index 2a78bf9f50..22b59a394f 100644
--- a/tests/testthat/test-function-args.R
+++ b/tests/testthat/test-function-args.R
@@ -22,7 +22,7 @@ test_that("geom_xxx and GeomXxx$draw arg defaults match", {
   lapply(geom_fun_names, function(geom_fun_name) {
     geom_fun    <- ggplot2_ns[[geom_fun_name]]
     geom <- geom_fun()$geom
-    if (!inherits(geom, "Geom")) # for geoms that return more than one thing
+    if (!is_geom(geom)) # for geoms that return more than one thing
       return()
 
     fun_args <- formals(geom_fun)
diff --git a/tests/testthat/test-theme.R b/tests/testthat/test-theme.R
index 895d4cf9fc..6c2a2b5a68 100644
--- a/tests/testthat/test-theme.R
+++ b/tests/testthat/test-theme.R
@@ -19,10 +19,10 @@ test_that("modifying theme element properties with + operator works", {
   t <- theme_grey() + theme(axis.title.x = element_text(colour = 'red', margin = margin()))
   expect_identical(t$axis.title.x, element_text(colour = 'red', margin = margin(), vjust = 1))
   # Make sure the theme class didn't change or get dropped
-  expect_true(is.theme(t))
+  expect_s3_class(t, "theme")
   # Make sure the element class didn't change or get dropped
-  expect_true(inherits(t$axis.title.x, "element"))
-  expect_true(inherits(t$axis.title.x, "element_text"))
+  expect_s3_class(t$axis.title.x, "element")
+  expect_s3_class(t$axis.title.x, "element_text")
 
   # Modifying an intermediate node works
   t <- theme_grey() + theme(axis.title = element_text(colour = 'red'))
@@ -103,7 +103,7 @@ test_that("replacing theme elements with %+replace% operator 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))
+  expect_s3_class(t, "theme")
 
   # Changing an intermediate node works
   t <- theme_grey() %+replace% theme(axis.title = element_text(colour = 'red'))
@@ -337,7 +337,7 @@ test_that("element tree can be modified", {
 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")) {
+      if (is_element(el) && !is_element(el, "blank")) {
         el$inherit.blank
       } else {
         TRUE
@@ -778,7 +778,7 @@ test_that("Legends can on all sides of the plot with custom justification", {
 test_that("Strips can render custom elements", {
   element_test <- function(...) {
     el <- element_text(...)
-    class(el) <- c('element_test', 'element_text', 'element')
+    class(el) <- c("element_test", "element_text", "element")
     el
   }
   element_grob.element_test <- function(element, label = "", x = NULL, y = NULL, ...) {