diff --git a/tests/testthat/test-detect_mad.R b/tests/testthat/test-detect_mad.R
index cb6c511..dd4c6e3 100644
--- a/tests/testthat/test-detect_mad.R
+++ b/tests/testthat/test-detect_mad.R
@@ -44,3 +44,7 @@ test_that("`get_mad` function define the output values correctly", {
   }
 
 })
+
+test_that("errors are produced as expected", {
+  expect_error(get_mad(NULL, 0, 1, 1, 0))
+})
diff --git a/tests/testthat/test-detect_milkmf.R b/tests/testthat/test-detect_milkmf.R
index 9687778..3a29554 100644
--- a/tests/testthat/test-detect_milkmf.R
+++ b/tests/testthat/test-detect_milkmf.R
@@ -1,7 +1,5 @@
 
 
-library(riycf)
-
 
 ################################################################################
 # Return result values check
@@ -59,3 +57,9 @@ test_that("`get_mmff` function define the output values correctly", {
   }
 
 })
+
+
+test_that("errors are produced as expected", {
+  expect_error(get_mmff(0, 2, NULL))
+  expect_error(get_milk_frq(0, 0, 0, NULL))
+})
\ No newline at end of file