If function name is omitted, it will be the variable name (implicit name).
If function name is present, it will be the function name (explicit name).

const foo = function () {};
foo.name // "foo"
const foo2 = foo;
foo2.name // "foo"
const bar = function baz() {};
bar.name // "baz"

diff --git a/Exercises/4-methods.test b/Exercises/4-methods.test
index a408b22..78eb07d 100644
--- a/Exercises/4-methods.test
+++ b/Exercises/4-methods.test
@@ -10,11 +10,15 @@
 },
 m3(x, y, z) {
 return [x, y, z];
- }
+ },
+ m4: function sum(x, y) {
+ return x + y;
+ },
 }, [
 ['m1', 1],
 ['m2', 2],
- ['m3', 3]
+ ['m3', 3],
+ ['sum', 2],
 ]
 ],
 ]