diff --git a/DESCRIPTION b/DESCRIPTION
index 2d1a9a5..4eec4ce 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -2,7 +2,7 @@ Package: ggpp
 Type: Package
 Title: Grammar Extensions to 'ggplot2'
 Version: 0.5.6.9001
-Date: 2024-03-04
+Date: 2024-04-18
 Authors@R:
     c(
     person("Pedro J.", "Aphalo", email = "pedro.aphalo@helsinki.fi", role = c("aut", "cre"), comment = c(ORCID = "0000-0003-3385-972X")),
diff --git a/tests/testthat/Rplots.pdf b/tests/testthat/Rplots.pdf
index c9a5d03..f18ce1a 100644
Binary files a/tests/testthat/Rplots.pdf and b/tests/testthat/Rplots.pdf differ
diff --git a/tests/testthat/test-compute_npc.R b/tests/testthat/test-compute_npc.R
new file mode 100644
index 0000000..0ada33b
--- /dev/null
+++ b/tests/testthat/test-compute_npc.R
@@ -0,0 +1,39 @@
+context("compute_npc")
+
+test_that("character input value returns correct numeric value", {
+  expect_equal(compute_npc("right"), 0.95)
+  expect_equal(compute_npc("left"), 0.05)
+  expect_equal(compute_npc(c("left", "right")), c(0.05, 0.95))
+  expect_equal(compute_npc("centre"), 0.5)
+  expect_equal(compute_npc("center"), 0.5)
+  expect_equal(compute_npc("middle"), 0.5)
+  expect_equal(compute_npc("bottom"), 0.05)
+  expect_equal(compute_npc("top"), 0.95)
+})
+
+test_that("factor input values returns correct numeric value", {
+  x <- factor(c("right", "left"))
+  expect_equal(compute_npc(x), c(0.95, 0.05))
+
+})
+
+test_that("numeric input value returns the same value if
+          between 0 and 1", {
+  x <- c(0.5, 1)
+  expect_equal(compute_npc(x), x)
+})
+
+test_that("numeric input value
+          returns 0 if less than 0,
+          returns 1 if greater than 1", {
+            x <- c(-0.5, 2)
+            expect_equal(compute_npc(x), c(0,1))
+          })
+
+test_that("Value is returned 'AsIs'", {
+  expect_is(as_npc("right"), "AsIs")
+  expect_equal(as_npc("right"), I(0.95))
+  expect_equal(as_npc("left"), I(0.05))
+  expect_equal(as_npc("centre"), I(0.5))
+  expect_equal(as_npc("center"), I(0.5))
+})
diff --git a/tests/testthat/test-compute_npcx.R b/tests/testthat/test-compute_npcx.R
index 0be8df8..4d453c0 100644
--- a/tests/testthat/test-compute_npcx.R
+++ b/tests/testthat/test-compute_npcx.R
@@ -28,3 +28,11 @@ test_that("numeric input value
             x <- c(-0.5, 2)
             expect_equal(compute_npcx(x), c(0,1))
           })
+
+test_that("Value is returned 'AsIs'", {
+  expect_is(as_npcx("right"), "AsIs")
+  expect_equal(as_npcx("right"), I(0.95))
+  expect_equal(as_npcx("left"), I(0.05))
+  expect_equal(as_npcx("centre"), I(0.5))
+  expect_equal(as_npcx("center"), I(0.5))
+})
diff --git a/tests/testthat/test-compute_npcy.R b/tests/testthat/test-compute_npcy.R
index 676ae68..83d3e1b 100644
--- a/tests/testthat/test-compute_npcy.R
+++ b/tests/testthat/test-compute_npcy.R
@@ -29,3 +29,12 @@ test_that("numeric input values
             expect_equal(compute_npcy(y), c(0,1))
           })
 
+test_that("Value is returned 'AsIs'", {
+  expect_is(as_npcy("top"), "AsIs")
+  expect_equal(as_npcy("top"), I(0.95))
+  expect_equal(as_npcy("bottom"), I(0.05))
+  expect_equal(as_npcy("middle"), I(0.5))
+  expect_equal(as_npcx("center"), I(0.5))
+  expect_equal(as_npcx("centre"), I(0.5))
+})
+
diff --git a/tests/testthat/test-geom-text.R b/tests/testthat/test-geom-text.R
index c3b3711..881e61e 100644
--- a/tests/testthat/test-geom-text.R
+++ b/tests/testthat/test-geom-text.R
@@ -25,5 +25,24 @@ test_that("multiple_rows_tb", {
                                 geom_text_npc(data = df,
                                               mapping = aes(npcx = x, npcy = y, label = to.parse),
                                               parse = TRUE))
+  expect_error(
+    ggplot(data = mtcars) +
+      geom_point(mapping = aes(wt, mpg)) +
+      geom_text_npc(data = df,
+                    mapping = aes(npcx = x, npcy = y, label = to.parse),
+                    parse = TRUE,
+                    nudge_y = 0.1,
+                    position = "stack")
+  )
+
+  expect_no_error(
+    ggplot(data = mtcars) +
+      geom_point(mapping = aes(wt, mpg)) +
+      geom_text_npc(data = df,
+                    mapping = aes(npcx = x, npcy = y, label = to.parse),
+                    parse = TRUE,
+                    nudge_x = 0.1,
+                    position = "identity")
+  )
 })