diff --git a/src/main/kotlin/net/thauvin/erik/akismet/Akismet.kt b/src/main/kotlin/net/thauvin/erik/akismet/Akismet.kt
index 34615ee..7d392a2 100644
--- a/src/main/kotlin/net/thauvin/erik/akismet/Akismet.kt
+++ b/src/main/kotlin/net/thauvin/erik/akismet/Akismet.kt
@@ -343,10 +343,10 @@ open class Akismet(apiKey: String) {
                     if (response == "valid" || response == "true" || response.startsWith("Thanks")) {
                         return true
                     } else if (response != "false" && response != "invalid") {
-                        errorMessage = "Unexpected response: " + if (body.isBlank()) "(0-byte body)" else body
+                        errorMessage = "Unexpected response: " + if (body.isBlank()) "<blank>" else body
                     }
                 } else {
-                    val message = "An empty response was received from Akismet."
+                    val message = "No response body was received from Akismet."
                     errorMessage = if (debugHelp.isNotBlank()) {
                         "$message: $debugHelp"
                     } else {
diff --git a/src/test/kotlin/net/thauvin/erik/akismet/AkismetTest.kt b/src/test/kotlin/net/thauvin/erik/akismet/AkismetTest.kt
index b100b76..a5d1ac3 100644
--- a/src/test/kotlin/net/thauvin/erik/akismet/AkismetTest.kt
+++ b/src/test/kotlin/net/thauvin/erik/akismet/AkismetTest.kt
@@ -86,6 +86,7 @@ class AkismetTest {
     )
     private val akismet = Akismet(apiKey, blog)
     private val mockComment: AkismetComment = AkismetComment(request = getMockRequest())
+    private val emptyFormBody = FormBody.Builder().build()
 
     @BeforeClass
     fun beforeClass() {
@@ -191,7 +192,7 @@ class AkismetTest {
     fun testEmptyResponse() {
         assertTrue(
             akismet.executeMethod(
-                "https://postman-echo.com/status/200".toHttpUrlOrNull(), FormBody.Builder().build(), true
+                "https://postman-echo.com/status/200".toHttpUrlOrNull(), emptyFormBody, true
             )
         )
         val expected = "{\"status\":200}"
@@ -210,11 +211,15 @@ class AkismetTest {
     fun testProTipResponse() {
         assertFalse(
             akismet.executeMethod(
-                "https://postman-echo.com/response-headers?x-akismet-pro-tip=test".toHttpUrlOrNull(),
-                FormBody.Builder().build()
+                "https://postman-echo.com/response-headers?x-akismet-pro-tip=discard".toHttpUrlOrNull(),
+                emptyFormBody
             )
         )
-        assertEquals(akismet.proTip, "test")
+        assertEquals(akismet.proTip, "discard")
+        assertTrue(akismet.isDiscard, "isDiscard")
+
+        akismet.reset()
+        assertTrue(!akismet.isDiscard && akismet.response.isEmpty() && akismet.httpStatusCode == 0)
     }
 
     @Test
@@ -247,17 +252,29 @@ class AkismetTest {
         )
     }
 
+    @Test
+    fun invalidApiTest() {
+        akismet.executeMethod("https://.com".toHttpUrlOrNull(), emptyFormBody)
+        assertTrue(akismet.errorMessage.startsWith("Invalid API"))
+    }
+
+    @Test
+    fun ioErrorTest() {
+        akismet.executeMethod("https://www.doesnotexists.com".toHttpUrlOrNull(), emptyFormBody)
+        assertTrue(akismet.errorMessage.contains("IO error"))
+    }
+
     @Test
     fun submitHamTest() {
         assertTrue(akismet.submitHam(comment), "submitHam")
 
-        assertTrue(akismet.submitHam(mockComment), "submitHam(request)")
+        assertTrue(akismet.submitHam(mockComment), "submitHam(mock)")
     }
 
     @Test
     fun submitSpamTest() {
         assertTrue(akismet.submitSpam(comment), "submitHam")
-        assertTrue(akismet.submitSpam(mockComment), "submitHam(request)")
+        assertTrue(akismet.submitSpam(mockComment), "submitHam(mock)")
     }
 
     @Test
@@ -269,6 +286,8 @@ class AkismetTest {
 
         assertNotEquals(jsonComment, comment, "json is different")
         assertNotEquals(jsonComment.hashCode(), comment.hashCode(), "json hashcode is different")
+
+        assertNotEquals(this, comment, "wrong object")
     }
 
     @Test
@@ -300,7 +319,7 @@ class AkismetTest {
         Mockito.`when`(request.getHeader("Cookie")).thenReturn("name=value; name2=value2; name3=value3")
         Mockito.`when`(request.getHeader("Accept-Encoding")).thenReturn("gzip")
         Mockito.`when`(request.headerNames)
-            .thenReturn(Collections.enumeration(listOf("User-Agent", "referer", "Cookie", "Accept-Encoding")))
+            .thenReturn(Collections.enumeration(listOf("User-Agent", "referer", "Cookie", "Accept-Encoding", "Null")))
         return request
     }
 }