diff --git a/js/tests/debounce_test.js b/js/tests/debounce_test.js
index 9dea8278..46364513 100644
--- a/js/tests/debounce_test.js
+++ b/js/tests/debounce_test.js
@@ -67,7 +67,7 @@ t(async ({ eq }) =>
       run(opDebounce(add, 200, { leading: true }), { delay: 70, count: 3 }),
       run(opDebounce(add, 100, { leading: true }), { delay: 140, count: 3 }),
     ]),
-    [1, 2]
+    [1, 3]
   )
 )
 
diff --git a/js/tests/fusion_test.js b/js/tests/fusion_test.js
index 1a49e610..0473710b 100644
--- a/js/tests/fusion_test.js
+++ b/js/tests/fusion_test.js
@@ -65,22 +65,4 @@ t(({ eq }) =>
   )
 )
 
-t(({ eq }) =>
-  // object mutability
-  eq(
-    fusion(Object.freeze({ a: { b: 1 } }), Object.freeze({ a: { b: 2 } })).a.b,
-    3
-  )
-)
-
-// other types
-t(({ eq }) => eq(fusion({ reg: /\w/ }, { reg: /\S/ }).reg, /\S/))
-t(({ eq }) => {
-  const set = new Set([1, 2, 3])
-  return eq(fusion({ a: 1, set: new Set([4, 5, 6]) }, { a: 1, set }), {
-    a: 2,
-    set,
-  })
-})
-
 Object.freeze(tests)
diff --git a/subjects/fusion/README.md b/subjects/fusion/README.md
index 8bf3e55e..eaa79243 100644
--- a/subjects/fusion/README.md
+++ b/subjects/fusion/README.md
@@ -4,36 +4,37 @@
 
 The objective of this exercise is to merge objects into a new object depending on the values type
 
-With this create a function called `fusion` that:
+With this, create a function called `fusion` that:
 
-- If the type is an array you must concat it
+- If the type is an array you must concatenate it
 
 ```js
-fusion([1, 2], [3, 4]) // -> [1,2,3,4]
+fusion({ arr: [1, "2"] }, { arr: [2] }); // -> { arr: [ 1, '2', 2 ] }
+fusion({ arr: [], arr1: [5] },{ arr: [10, 3], arr1: [15, 3], arr2: ["7", "1"] }); // ->{ arr: [ 10, 3 ], arr1: [ 5, 15, 3 ], arr2: [ '7', '1' ] }
 ```
 
-- If it is a string you must concatenate with a space
+- If it is a string you must concatenate it with a space
 
 ```js
-fusion('Salem', 'alem') // -> 'Salem alem'
+fusion({ str: "salem" }, { str: "alem" }); // -> { str: 'salem alem' }
+fusion({ str: "salem" }, { str: "" }); // -> { str: 'salem ' }
 ```
 
-- If it is numbers you must added them
+- If they are numbers, you must add them
 
 ```js
-fusion(4, 11) // -> 15
+fusion({ a: 10, b: 8, c: 1 }, { a: 10, b: 2 }); // -> { a: 20, b: 10, c: 1 }
 ```
 
-- In case of type mismatch you must replace it with the value of the second object
+- If it is an object, you must join them recursively
 
 ```js
-fusion({ a: 'hello', b: [] }, { a: 4 })
-// -> { a: 4, b: [] }
+fusion({ a: 1, b: { c: "Salem" } }, { a: 10, x: [], b: { c: "alem" } }); // -> { a: 11, x: [], b: { c: 'Salem alem' } }
+fusion( { a: { b: [3, 2], c: { d: 8 } } },{ a: { b: [0, 3, 1], c: { d: 3 } } }); // -> { a: { b: [ 3, 2, 0, 3, 1 ], c: { d: 11 } } }
 ```
 
-- If it is an object you must fusion them recursively
+- In case of type mismatch you must replace it with the value of the second object
 
 ```js
-fusion({ a: 1, b: { c: 'Salem' } }, { a: 10, x: [], b: { c: 'alem' } })
-// -> { a: 11, x: [], b: { c: 'Salem alem' } }
+fusion({ a: "hello", b: [] }, { a: 4 }); // -> { a: 4, b: [] }
 ```