diff --git a/test/mood-line-test.el b/test/mood-line-test.el
index f89afb4..2a525ea 100644
--- a/test/mood-line-test.el
+++ b/test/mood-line-test.el
@@ -17,57 +17,80 @@
 ;; mood-line-defformat
 ;; ---------------------------------- ;;
 
-(ert-deftest -defformat/right-nil ()
-  "The format sequence should expand if the right segment list is not provided."
-  (should (equal (mood-line-defformat
-                  ;; Left
-                  ("XYZ")
-                  ;; Right
-                  )
+(ert-deftest -defformat/padding ()
+  "The expanded sequence should include the provided (or default) padding."
+  (should (equal (mood-line-defformat)
                  (list
                   ;; Left
-                  '("XYZ")
+                  '(" ")
                   ;; Right
-                  nil))))
-
-(ert-deftest -defformat/left-right ()
-  "The expanded sequence should should include left and right segments lists."
+                  '(" "))))
   (should (equal (mood-line-defformat
+                  :padding
+                  "---")
+                 (list
                   ;; Left
-                  ("ABC")
+                  '("---")
                   ;; Right
+                  '("---")))))
+
+(ert-deftest -defformat/left-right-nil ()
+  "The format sequence should expand if the left or right segment list is nil."
+  (should (equal (mood-line-defformat
+                  :left
                   ("XYZ"))
                  (list
                   ;; Left
-                  '("ABC")
+                  '(" " "XYZ")
                   ;; Right
-                  '("XYZ")))))
+                  '(" "))))
+  (should (equal (mood-line-defformat
+                  :right
+                  ("XYZ"))
+                 (list
+                  ;; Left
+                  '(" ")
+                  ;; Right
+                  '("XYZ" " ")))))
+
+(ert-deftest -defformat/left-right ()
+  "The expanded sequence should include left and right segments lists."
+  (should (equal (mood-line-defformat
+                  :left
+                  ("ABC")
+                  :right
+                  ("XYZ"))
+                 (list
+                  ;; Left
+                  '(" " "ABC")
+                  ;; Right
+                  '("XYZ" " ")))))
 
 (ert-deftest -defformat/cons-cells ()
   "Cons cell segments should expand into their `car' and `cdr' values."
   (should (equal (mood-line-defformat
-                  ;; Left
+                  :left
                   ("ABC" ("ABC" . "XYZ") "XYZ")
-                  ;; Right
+                  :right
                   ("..." ((some-fn) . " ") "..."))
                  (list
                   ;; Left
-                  '("ABC" "ABC" "XYZ" "XYZ")
+                  '(" " "ABC" "ABC" "XYZ" "XYZ")
                   ;; Right
-                  '("..." (some-fn) " " "...")))))
+                  '("..." (some-fn) " " "..." " ")))))
 
 (ert-deftest -defformat/exp-separators ()
   "Non-string, non-cons expressions should expand followed by a blank string."
   (should (equal (mood-line-defformat
-                  ;; Left
+                  :left
                   ("ABC" ("ABC" . "XYZ") some-exp "XYZ" (some-fn))
-                  ;; Right
+                  :right
                   ("..." ((some-fn) . " ") (another-fn) "..."))
                  (list
                   ;; Left
-                  '("ABC" "ABC" "XYZ" some-exp "" "XYZ" (some-fn) "")
+                  '(" " "ABC" "ABC" "XYZ" some-exp "" "XYZ" (some-fn) "")
                   ;; Right
-                  '("..." (some-fn) " " (another-fn) "" "...")))))
+                  '("..." (some-fn) " " (another-fn) "" "..." " ")))))
 
 ;; -------------------------------------------------------------------------- ;;
 ;;