diff --git a/k9mail-library/src/test/java/com/fsck/k9/mail/store/imap/ImapFolderTest.java b/k9mail-library/src/test/java/com/fsck/k9/mail/store/imap/ImapFolderTest.java
index d435c3243..f19d68a2b 100644
--- a/k9mail-library/src/test/java/com/fsck/k9/mail/store/imap/ImapFolderTest.java
+++ b/k9mail-library/src/test/java/com/fsck/k9/mail/store/imap/ImapFolderTest.java
@@ -42,6 +42,7 @@ import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.anyString;
 import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
@@ -451,6 +452,24 @@ public class ImapFolderTest {
         }
     }
 
+    @Test
+    public void getUnreadMessageCount_connectionThrowsIOException_shouldThrowMessagingException()
+            throws Exception {
+        ImapFolder folder = createFolder("Folder");
+        prepareImapFolderForOpen(OPEN_MODE_RW);
+        List<ImapResponse> imapResponses = singletonList(createImapResponse("* SEARCH 1 2 3"));
+        when(imapConnection.executeSimpleCommand("SEARCH 1:* UNSEEN NOT DELETED"))
+                .thenThrow(new IOException());
+        folder.open(OPEN_MODE_RW);
+
+        try {
+            folder.getUnreadMessageCount();
+            fail("Expected exception");
+        } catch (MessagingException e) {
+            assertEquals("IO Error", e.getMessage());
+        }
+    }
+
     @Test
     public void getUnreadMessageCount() throws Exception {
         ImapFolder folder = createFolder("Folder");
@@ -506,6 +525,36 @@ public class ImapFolderTest {
         assertEquals(42L, result);
     }
 
+    @Test
+    public void getHighestUid_imapConnectionThrowsNegativesResponse_shouldReturnMinus1() throws Exception {
+        ImapFolder folder = createFolder("Folder");
+        prepareImapFolderForOpen(OPEN_MODE_RW);
+        List<ImapResponse> imapResponses = singletonList(createImapResponse("* SEARCH 42"));
+        when(imapConnection.executeSimpleCommand("UID SEARCH *:*"))
+                .thenThrow(NegativeImapResponseException.class);
+        folder.open(OPEN_MODE_RW);
+
+        long result = folder.getHighestUid();
+
+        assertEquals(-1L, result);
+    }
+
+    @Test
+    public void getHighestUid_imapConnectionThrowsIOException_shouldThrowMessagingException() throws Exception {
+        ImapFolder folder = createFolder("Folder");
+        prepareImapFolderForOpen(OPEN_MODE_RW);
+        List<ImapResponse> imapResponses = singletonList(createImapResponse("* SEARCH 42"));
+        when(imapConnection.executeSimpleCommand("UID SEARCH *:*"))
+                .thenThrow(IOException.class);
+        folder.open(OPEN_MODE_RW);
+
+        try {
+            folder.getHighestUid();
+        } catch (MessagingException e) {
+            assertEquals("IO Error", e.getMessage());
+        }
+    }
+
     @Test
     public void getMessages_withoutDateConstraint() throws Exception {
         ImapFolder folder = createFolder("Folder");
@@ -724,6 +773,18 @@ public class ImapFolderTest {
         assertFalse(result);
     }
 
+    public void areMoreMessagesAvailable_withIndexOf1_shouldReturnFalseWithoutPerformingSearch() throws Exception {
+        ImapFolder folder = createFolder("Folder");
+        prepareImapFolderForOpen(OPEN_MODE_RW);
+        folder.open(OPEN_MODE_RW);
+
+        boolean result = folder.areMoreMessagesAvailable(1, null);
+
+        verify(imapConnection, never()).executeSimpleCommand(anyString());
+
+        assertFalse(result);
+    }
+
     @Test
     public void areMoreMessagesAvailable_withoutAdditionalMessages_shouldIssueSearchCommandsUntilAllMessagesSearched()
             throws Exception {
@@ -1022,6 +1083,25 @@ public class ImapFolderTest {
         }
     }
 
+    @Test
+    public void delete_notImplemented() throws MessagingException {
+        ImapFolder folder = createFolder("Folder");
+        try {
+            folder.delete(false);
+            fail("Error expected");
+        } catch (Error e) {
+        }
+    }
+
+    @Test
+    public void getMessageByUid_returnsNewImapMessage() throws MessagingException {
+        ImapFolder folder = createFolder("Folder");
+        ImapMessage message = folder.getMessage("uid");
+        assertNotNull(message);
+        assertEquals("uid", message.getUid());
+        assertEquals(folder, message.getFolder());
+    }
+
     private Set<String> extractMessageUids(List<ImapMessage> messages) {
         Set<String> result = new HashSet<>();
         for (Message message : messages) {