diff --git a/tests/testthat/test-scale-manual.r b/tests/testthat/test-scale-manual.r
index b8af871e99..d33fe17da8 100644
--- a/tests/testthat/test-scale-manual.r
+++ b/tests/testthat/test-scale-manual.r
@@ -1,9 +1,13 @@
 context("scale_manual")
 
 test_that("names of values used in manual scales", {
-   s <- scale_colour_manual(values = c("8" = "c","4" = "a","6" = "b"))
-   s$train(c("4", "6", "8"))
-   expect_equal(s$map(c("4", "6", "8")), c("a", "b", "c"))
+   s1 <- scale_colour_manual(values = c("8" = "c", "4" = "a", "6" = "b"))
+   s1$train(c("4", "6", "8"))
+   expect_equal(s1$map(c("4", "6", "8")), c("a", "b", "c"))
+
+   s2 <- scale_colour_manual(values = c("8" = "c", "4" = "a", "6" = "b"), na.value = NA)
+   s2$train(c("4", "8"))
+   expect_equal(s2$map(c("4", "6", "8")), c("a", NA, "c"))
 })
 
 
@@ -87,13 +91,53 @@ test_that("unnamed values match breaks in manual scales", {
 })
 
 test_that("limits works (#3262)", {
-  # named charachter vector
+  # named character vector
   s1 <- scale_colour_manual(values = c("8" = "c", "4" = "a", "6" = "b"), limits = c("4", "8"), na.value = NA)
   s1$train(c("4", "6", "8"))
   expect_equal(s1$map(c("4", "6", "8")), c("a", NA, "c"))
 
-  # named charachter vector
+  # unnamed character vector
   s2 <- scale_colour_manual(values = c("c", "a", "b"), limits = c("4", "8"), na.value = NA)
   s2$train(c("4", "6", "8"))
   expect_equal(s2$map(c("4", "6", "8")), c("c", NA, "a"))
 })
+
+test_that("fewer values (#3451)", {
+  # named character vector
+  s1 <- scale_colour_manual(values = c("4" = "a", "8" = "c"), na.value = NA)
+  s1$train(c("4", "6", "8"))
+  expect_equal(s1$map(c("4", "6", "8")), c("a", NA, "c"))
+
+  # unnamed character vector
+  s2 <- scale_colour_manual(values = c("4", "8"), na.value = NA)
+  s2$train(c("4", "6", "8"))
+  expect_error(s2$map(c("4", "6", "8")), "Insufficient values")
+})
+
+test_that("limits and breaks (#4619)", {
+  # values don't change legend order
+  s1 <- scale_colour_manual(
+    values = c("8" = "c", "4" = "a", "6" = "b"),
+  )
+  s1$train(c("8", "6", "4"))
+  expect_equal(s1$map(c("8", "6", "4")), c("c", "b", "a"))
+  expect_equal(s1$break_positions(), c("a", "b", "c"))
+
+  # limits change legend order
+  s2 <- scale_colour_manual(
+    values = c("8" = "c", "4" = "a", "6" = "b", "0" = "x"),
+    limits = c("0", "4", "6", "8")
+  )
+  s2$train(c("8", "6", "4"))
+  expect_equal(s2$map(c("4", "6", "8")), c("a", "b", "c"))
+  expect_equal(s2$break_positions(), c("x", "a", "b", "c"))
+
+  # breaks work
+  s3 <- scale_colour_manual(
+    values = c("8" = "c", "4" = "a", "6" = "b"),
+    breaks = c("4", "8")
+  )
+  s3$train(c("4", "6", "8"))
+  expect_equal(s3$map(c("4", "6", "8")), c("a", "b", "c"))
+  expect_equal(s3$break_positions(), c("a", "c"))
+})