diff --git a/tests/testthat/test-testThenRank.R b/tests/testthat/test-testThenRank.R
index d03b6e5..f00974a 100644
--- a/tests/testthat/test-testThenRank.R
+++ b/tests/testthat/test-testThenRank.R
@@ -1,108 +1,232 @@
 test_that("test-then-rank raises warning for one case", {
   data <- rbind(
     data.frame(algo="A1", value=0.6, case="C1"),
     data.frame(algo="A2", value=0.8, case="C1"))
 
   challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
 
   expect_warning(ranking <- challenge%>%testThenRank(),
                  "Only one case in task.", fixed = TRUE)
 
   expectedRanking <- rbind(
     "A1" = data.frame(prop_significance = 0, rank = 1),
     "A2" = data.frame(prop_significance = 0, rank = 1))
 
   expect_equal(ranking$matlist$T1, expectedRanking)
 })
 
 test_that("test-then-rank works with two algorithms, small values are better", {
   data <- rbind(
     data.frame(algo="A1", value=0.2, case="C1"),
     data.frame(algo="A1", value=0.2, case="C2"),
     data.frame(algo="A1", value=0.2, case="C3"),
     data.frame(algo="A1", value=0.2, case="C4"),
     data.frame(algo="A2", value=1.0, case="C1"),
     data.frame(algo="A2", value=1.0, case="C2"),
     data.frame(algo="A2", value=1.0, case="C3"),
     data.frame(algo="A2", value=1.0, case="C4"))
 
   challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
 
   ranking <- challenge%>%testThenRank()
 
   expectedRanking <- rbind(
     "A1" = data.frame(prop_significance = 1, rank = 1),
     "A2" = data.frame(prop_significance = 0, rank = 2))
 
   expect_equal(ranking$matlist$T1, expectedRanking)
 })
 
 test_that("test-then-rank works with two algorithms, large values are better", {
   data <- rbind(
     data.frame(algo="A1", value=0.2, case="C1"),
     data.frame(algo="A1", value=0.2, case="C2"),
     data.frame(algo="A1", value=0.2, case="C3"),
     data.frame(algo="A1", value=0.2, case="C4"),
     data.frame(algo="A2", value=1.0, case="C1"),
     data.frame(algo="A2", value=1.0, case="C2"),
     data.frame(algo="A2", value=1.0, case="C3"),
     data.frame(algo="A2", value=1.0, case="C4"))
 
   challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = FALSE)
 
   ranking <- challenge%>%testThenRank()
 
   expectedRanking <- rbind(
     "A1" = data.frame(prop_significance = 0, rank = 2),
     "A2" = data.frame(prop_significance = 1, rank = 1))
 
   expect_equal(ranking$matlist$T1, expectedRanking)
 })
 
 test_that("test-then-rank works for ties method 'max'", {
   data <- rbind(
     data.frame(algo="A1", value=0.6, case="C1"),
     data.frame(algo="A1", value=0.6, case="C2"),
     data.frame(algo="A2", value=0.8, case="C1"),
     data.frame(algo="A2", value=0.8, case="C2"))
 
   challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
 
   ranking <- challenge%>%testThenRank(ties.method = "max")
 
   expectedRanking <- rbind(
     "A1" = data.frame(prop_significance = 0, rank = 2),
     "A2" = data.frame(prop_significance = 0, rank = 2))
 
   expect_equal(ranking$matlist$T1, expectedRanking)
 })
 
 test_that("test-then-rank raises error for invalid ties method", {
   data <- rbind(
     data.frame(algo="A1", value=0.6, case="C1"),
     data.frame(algo="A1", value=0.6, case="C2"),
     data.frame(algo="A2", value=0.8, case="C1"),
     data.frame(algo="A2", value=0.8, case="C2"))
 
   challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
 
-  expect_error(challenge%>%testThenRank(FUN = mean, ties.method = "maxx"),
+  expect_error(challenge%>%testThenRank(ties.method = "maxx"),
                "'arg' should be one of \"average\", \"first\", \"last\", \"random\", \"max\", \"min\"", fixed = TRUE)
 })
 
 test_that("test-then-rank raises error for invalid ties method even when no ties present", {
   data <- rbind(
     data.frame(algo="A1", value=0.2, case="C1"),
     data.frame(algo="A1", value=0.2, case="C2"),
     data.frame(algo="A1", value=0.2, case="C3"),
     data.frame(algo="A1", value=0.2, case="C4"),
     data.frame(algo="A2", value=1.0, case="C1"),
     data.frame(algo="A2", value=1.0, case="C2"),
     data.frame(algo="A2", value=1.0, case="C3"),
     data.frame(algo="A2", value=1.0, case="C4"))
 
   challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
 
-  expect_error(challenge%>%testThenRank(FUN = mean, ties.method = "maxx"),
+  expect_error(challenge%>%testThenRank(ties.method = "maxx"),
                "'arg' should be one of \"average\", \"first\", \"last\", \"random\", \"max\", \"min\"", fixed = TRUE)
 })
+
+test_that("test-then-rank raises error when no NA treatment specified but NAs are contained", {
+  data <- rbind(
+    data.frame(algo="A1", value=NA, case="C1"),
+    data.frame(algo="A1", value=0.2, case="C2"),
+    data.frame(algo="A1", value=0.2, case="C3"),
+    data.frame(algo="A1", value=0.2, case="C4"),
+    data.frame(algo="A2", value=1.0, case="C1"),
+    data.frame(algo="A2", value=1.0, case="C2"),
+    data.frame(algo="A2", value=1.0, case="C3"),
+    data.frame(algo="A2", value=1.0, case="C4"))
+
+  challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
+
+  expect_error(challenge%>%testThenRank(),
+               "argument \"na.treat\" is missing, with no default", fixed = TRUE)
+})
+
+test_that("test-then-rank raises error when invalid NA treatment specified and NAs are contained", {
+  data <- rbind(
+    data.frame(algo="A1", value=NA, case="C1"),
+    data.frame(algo="A1", value=0.2, case="C2"),
+    data.frame(algo="A1", value=0.2, case="C3"),
+    data.frame(algo="A1", value=0.2, case="C4"),
+    data.frame(algo="A2", value=1.0, case="C1"),
+    data.frame(algo="A2", value=1.0, case="C2"),
+    data.frame(algo="A2", value=1.0, case="C3"),
+    data.frame(algo="A2", value=1.0, case="C4"))
+
+  challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
+
+  expect_error(challenge%>%testThenRank(na.treat = "na.rmx"),
+               "Argument 'na.treat' is invalid. It can be 'na.rm', numeric value or function.", fixed = TRUE)
+})
+
+test_that("specified NA treatment does not influence ranking when no NAs are contained", {
+  data <- rbind(
+    data.frame(algo="A1", value=0.2, case="C1"),
+    data.frame(algo="A1", value=0.2, case="C2"),
+    data.frame(algo="A1", value=0.2, case="C3"),
+    data.frame(algo="A1", value=0.2, case="C4"),
+    data.frame(algo="A2", value=1.0, case="C1"),
+    data.frame(algo="A2", value=1.0, case="C2"),
+    data.frame(algo="A2", value=1.0, case="C3"),
+    data.frame(algo="A2", value=1.0, case="C4"))
+
+  challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
+
+  ranking <- challenge%>%testThenRank(na.treat = 0)
+
+  expectedRanking <- rbind(
+    "A1" = data.frame(prop_significance = 1, rank = 1),
+    "A2" = data.frame(prop_significance = 0, rank = 2))
+
+  expect_equal(ranking$matlist$T1, expectedRanking)
+})
+
+test_that("NAs are replaced by numeric value", {
+  data <- rbind(
+    data.frame(algo="A1", value=NA, case="C1"),
+    data.frame(algo="A1", value=0.2, case="C2"),
+    data.frame(algo="A1", value=0.2, case="C3"),
+    data.frame(algo="A1", value=0.2, case="C4"),
+    data.frame(algo="A2", value=1.0, case="C1"),
+    data.frame(algo="A2", value=1.0, case="C2"),
+    data.frame(algo="A2", value=1.0, case="C3"),
+    data.frame(algo="A2", value=1.0, case="C4"))
+
+  challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
+
+  ranking <- challenge%>%testThenRank(na.treat = 100.0)
+
+  expectedRanking <- rbind(
+    "A1" = data.frame(prop_significance = 0, rank = 1),
+    "A2" = data.frame(prop_significance = 0, rank = 1))
+
+  expect_equal(ranking$matlist$T1, expectedRanking)
+})
+
+test_that("NAs are replaced by function value", {
+  data <- rbind(
+    data.frame(algo="A1", value=NA, case="C1"),
+    data.frame(algo="A1", value=0.2, case="C2"),
+    data.frame(algo="A1", value=0.2, case="C3"),
+    data.frame(algo="A1", value=0.2, case="C4"),
+    data.frame(algo="A2", value=1.0, case="C1"),
+    data.frame(algo="A2", value=1.0, case="C2"),
+    data.frame(algo="A2", value=1.0, case="C3"),
+    data.frame(algo="A2", value=1.0, case="C4"))
+
+  replacementFunction <- function(x) { 0.0 }
+
+  challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
+
+  ranking <- challenge%>%testThenRank(na.treat = replacementFunction)
+
+  expectedRanking <- rbind(
+    "A1" = data.frame(prop_significance = 1, rank = 1),
+    "A2" = data.frame(prop_significance = 0, rank = 2))
+
+  expect_equal(ranking$matlist$T1, expectedRanking)
+})
+
+test_that("NAs are removed", {
+  data <- rbind(
+    data.frame(algo="A1", value=NA, case="C1"),
+    data.frame(algo="A1", value=0.2, case="C2"),
+    data.frame(algo="A1", value=0.2, case="C3"),
+    data.frame(algo="A1", value=0.2, case="C4"),
+    data.frame(algo="A2", value=1.0, case="C1"),
+    data.frame(algo="A2", value=1.0, case="C2"),
+    data.frame(algo="A2", value=1.0, case="C3"),
+    data.frame(algo="A2", value=1.0, case="C4"))
+
+  challenge <- as.challenge(data, taskName="T1", algorithm="algo", case="case", value="value", smallBetter = TRUE)
+
+  ranking <- challenge%>%testThenRank(na.treat = "na.rm")
+
+  expectedRanking <- rbind(
+    "A1" = data.frame(prop_significance = 0, rank = 1),
+    "A2" = data.frame(prop_significance = 0, rank = 1))
+
+  expect_equal(ranking$matlist$T1, expectedRanking)
+})