diff --git a/src/utils/groupBy.test.js b/src/utils/groupBy.test.js
index eddd03a..8b055d9 100644
--- a/src/utils/groupBy.test.js
+++ b/src/utils/groupBy.test.js
@@ -2,46 +2,56 @@
 
 // 어떤 것을 해볼까요?
 const groupBy = (arr, callback) => {
-  return arr;
+  return arr.reduce((acc, val) => {
+    const key = callback(val);
+
+    if (acc[key] === undefined) acc[key] = [];
+
+    acc[key].push(val);
+    return acc;
+  }, {});
 };
 
-describe('groupBy 테스트', () => {
-  describe('non-lazy', () => {
-    it('case: 1, Normal', () => {
+describe("groupBy 테스트", () => {
+  describe("non-lazy", () => {
+    it("case: 1, Normal", () => {
       const array = [6.1, 4.2, 6.3];
       const grouped = groupBy(array, Math.floor);
 
       expect(grouped).toEqual({ 4: [4.2], 6: [6.1, 6.3] });
     });
 
-    it('case: 2, Advanced', () => {
+    it("case: 2, Advanced", () => {
       const array = [
-        [1, 'a'],
-        [2, 'a'],
-        [2, 'b'],
+        [1, "a"],
+        [2, "a"],
+        [2, "b"],
       ];
 
       // 두 번째 인자가 index
-      const [groupedFirstIndex, groupedSecondIndex] = [groupBy(array, 0), groupBy(array, 1)];
+      const [groupedFirstIndex, groupedSecondIndex] = [
+        groupBy(array, 0),
+        groupBy(array, 1),
+      ];
 
       expect(groupedFirstIndex).toEqual({
-        1: [[1, 'a']],
+        1: [[1, "a"]],
         2: [
-          [2, 'a'],
-          [2, 'b'],
+          [2, "a"],
+          [2, "b"],
         ],
       });
 
       expect(groupedSecondIndex).toEqual({
         a: [
-          [1, 'a'],
-          [2, 'a'],
+          [1, "a"],
+          [2, "a"],
         ],
-        b: [[2, 'b']],
+        b: [[2, "b"]],
       });
     });
 
-    it('case: 3, Advanced', () => {
+    it("case: 3, Advanced", () => {
       const grouped = groupBy({ a: 6.1, b: 4.2, c: 6.3 }, Math.floor);
 
       expect(grouped).toEqual({ 4: [4.2], 6: [6.1, 6.3] });
diff --git a/src/utils/unique.test.js b/src/utils/unique.test.js
index b5f3a92..5d793d4 100644
--- a/src/utils/unique.test.js
+++ b/src/utils/unique.test.js
@@ -2,12 +2,16 @@
 
 // 어떤 것을 해볼까요?
 const unique = (arr, callback, isSorted) => {
-  return arr;
+  const result = arr.reduce((acc, v) => {
+    return acc.includes(v) ? acc : [...acc, v];
+  }, []);
+
+  return result;
 };
 
-describe('unique 테스트', () => {
-  describe('non-lazy', () => {
-    it('case: 1, Normal', () => {
+describe("unique 테스트", () => {
+  describe("non-lazy", () => {
+    it("case: 1, Normal", () => {
       const [firstArray, secondArray] = [
         [2, 1, 2],
         [1, 2, 1],
@@ -19,7 +23,7 @@ describe('unique 테스트', () => {
       expect(secondUniqueArray).toEqual([1, 2]);
     });
 
-    it('case: 2, Advanced', () => {
+    it("case: 2, Advanced", () => {
       const [firstArray, secondArray, thirdArray] = [
         [1, 2, 3],
         [1, 1, 2, 2, 3],
@@ -34,7 +38,7 @@ describe('unique 테스트', () => {
       expect(thirdUniqueArray).toEqual([1, 2, 3]);
     });
 
-    it('case: 3, Advanced', () => {
+    it("case: 3, Advanced", () => {
       const objects = [
         { x: 1, y: 2 },
         { x: 2, y: 1 },