diff --git a/R/DEqual.R b/R/DEqual.R
index 7ce43b6..88f33f2 100644
--- a/R/DEqual.R
+++ b/R/DEqual.R
@@ -45,7 +45,7 @@ DEqual <- function(DE) {
     # stopifnot(!is.null(rownames(DE)))
     
     # Check if input is a dataframe
-    if (!is.data.frame(DE)) { stop("Error: The input is not a dataframe") }
+    if (!is.data.frame(DE)) { stop("Error: The input to DEqual is not a dataframe.") }
 
     # Check if 't' is in the column names of DE
       if (!("t" %in% colnames(DE))) {
diff --git a/tests/testthat/test-DEqual.R b/tests/testthat/test-DEqual.R
index d7f8cd7..04f4c2c 100644
--- a/tests/testthat/test-DEqual.R
+++ b/tests/testthat/test-DEqual.R
@@ -17,6 +17,12 @@ test_that("Input to DEqual is a dataframe", {
   # Test if the input to DEqual is a dataframe
   expect_true(is.data.frame(random_de), "The input to DEqual is not a dataframe.")
 })
+ 
+# Test if DEqual throws an error when input is not a dataframe
+test_that("DEqual throws an error for non-dataframe input", {
+  # Test if DEqual throws an error when input is not a dataframe
+  expect_error(DEqual(covComb_tx_deg), "Error: The input to DEqual is not a dataframe.")
+})
 
 # Test that the output is a ggplot object
 test_that("output is a ggplot", {