diff --git a/elisp/day-4/advent-of-code.el b/elisp/day-4/advent-of-code.el
new file mode 120000
index 0000000..4a02002
--- /dev/null
+++ b/elisp/day-4/advent-of-code.el
@@ -0,0 +1 @@
+../advent-of-code.el
\ No newline at end of file
diff --git a/elisp/day-4/example.txt b/elisp/day-4/example.txt
new file mode 120000
index 0000000..aaad177
--- /dev/null
+++ b/elisp/day-4/example.txt
@@ -0,0 +1 @@
+../../input/day-4-example.txt
\ No newline at end of file
diff --git a/elisp/day-4/input.txt b/elisp/day-4/input.txt
new file mode 120000
index 0000000..a52d0a3
--- /dev/null
+++ b/elisp/day-4/input.txt
@@ -0,0 +1 @@
+../../input/day-4.txt
\ No newline at end of file
diff --git a/elisp/day-4/solution.el b/elisp/day-4/solution.el
index 14aafa9..e1700a0 100755
--- a/elisp/day-4/solution.el
+++ b/elisp/day-4/solution.el
@@ -17,18 +17,11 @@
 ;; You should have received a copy of the GNU General Public License
 ;; along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-(add-to-list 'load-path "../")
+(add-to-list 'load-path default-directory)
 
 (require 'ert)
-(require 'cl-lib)
 (require 'advent-of-code)
 
-(defvar solution-input
-  "../../input/day-4.txt")
-
-(defvar solution-example-input
-  "../../input/day-4-example.txt")
-
 (defun solution-parse-pair (s)
   (let ((parts (string-split s "-")))
     (cons (string-to-number (car parts))
@@ -64,16 +57,20 @@
                pairs)))
 
 (ert-deftest solution-part-1-example ()
-  (should (equal (solution-part-1 (aoc-read-file-lines solution-example-input)) 2)))
+  (should (equal (solution-part-1 (aoc-read-file-lines "example.txt")) 2)))
 
 (ert-deftest solution-part-1 ()
-  (should (equal (solution-part-1 (aoc-read-file-lines solution-input)) 644)))
+  (should (equal (solution-part-1 (aoc-read-file-lines "input.txt")) 644)))
+
+(ert-deftest solution-part-2-example ()
+  (should (equal (solution-part-2 (aoc-read-file-lines "example.txt")) 4)))
+
+(ert-deftest solution-part-2 ()
+  (should (equal (solution-part-2 (aoc-read-file-lines "input.txt")) 926)))
 
 (when noninteractive
   (ert-run-tests-batch))
 
-;; Code
-
 ;; Local Variables:
 ;; read-symbol-shorthands: (("solution-" . "advent-of-code-day-4-") ("aoc-" . "advent-of-code-"))
 ;; End: