private IndexedSkypeMailFolder createIndexedSkypeMailFolder(FolderIndexMock folderIndex) { final FolderMock nonIndexedFolder = new FolderMock(); folderIndex.addSignatureForId("#42$foo", "previous-signature"); NonIndexGmailFolderProvider nonIndexedFolderMock = new NonIndexGmailFolderProvider() { @Override public SkypeMailFolder get() { return nonIndexedFolder; } }; IndexedSkypeMailFolder indexedGmailFolder = new IndexedSkypeMailFolder(nonIndexedFolderMock, folderIndex); addPreviousMessages(indexedGmailFolder); return indexedGmailFolder; }