diff --git a/sdk/src/test/java/co/omise/android/ui/ExpiryDateEditTextTest.kt b/sdk/src/test/java/co/omise/android/ui/ExpiryDateEditTextTest.kt
index 56696ce88..4da433327 100644
--- a/sdk/src/test/java/co/omise/android/ui/ExpiryDateEditTextTest.kt
+++ b/sdk/src/test/java/co/omise/android/ui/ExpiryDateEditTextTest.kt
@@ -57,6 +57,20 @@ class ExpiryDateEditTextTest {
         assertEquals("12/34", editText.text.toString())
     }
 
+    @Test
+    fun inputLengthExceedsMaxChars() {
+        val s = "123456" // 6 characters, assuming MAX_CHARS is 5
+        s.forEach { editText.append(it.toString()) }
+        assertEquals("12/34", editText.text.toString()) // assuming that exceeding chars will not be appended
+    }
+
+    @Test
+    fun inputContainsNonNumericOrSeparator() {
+        val s = "12ab" // 'ab' are non-numeric characters
+        s.forEach { editText.append(it.toString()) }
+        assertEquals("12/", editText.text.toString()) // assuming that non-numeric characters are not appended
+    }
+
     @Test(expected = InputValidationException.EmptyInputException::class)
     fun validate_emptyValue() {
         "".forEach { editText.append(it.toString()) }