diff --git a/package-lock.json b/package-lock.json
index 51a726bb..83b053aa 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -11,7 +11,8 @@
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+        "vite": "^5.0.0",
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@@ -366,6 +367,13 @@
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@@ -522,6 +530,201 @@
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+      "license": "MIT",
+      "dependencies": {
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+        "check-error": "^2.1.1",
+        "deep-eql": "^5.0.1",
+        "loupe": "^3.1.0",
+        "pathval": "^2.0.0"
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+    "node_modules/check-error": {
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+      "dev": true,
+      "license": "MIT",
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+      "resolved": "https://registry.npmjs.org/debug/-/debug-4.4.0.tgz",
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+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "ms": "^2.1.3"
+      },
+      "engines": {
+        "node": ">=6.0"
+      },
+      "peerDependenciesMeta": {
+        "supports-color": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/deep-eql": {
+      "version": "5.0.2",
+      "resolved": "https://registry.npmjs.org/deep-eql/-/deep-eql-5.0.2.tgz",
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+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=6"
+      }
+    },
     "node_modules/delay": {
       "version": "6.0.0",
       "resolved": "https://registry.npmjs.org/delay/-/delay-6.0.0.tgz",
@@ -533,6 +736,13 @@
         "url": "https://github.com/sponsors/sindresorhus"
       }
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+    "node_modules/es-module-lexer": {
+      "version": "1.6.0",
+      "resolved": "https://registry.npmjs.org/es-module-lexer/-/es-module-lexer-1.6.0.tgz",
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+      "dev": true,
+      "license": "MIT"
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@@ -570,6 +780,26 @@
         "@esbuild/win32-x64": "0.19.8"
       }
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+    "node_modules/estree-walker": {
+      "version": "3.0.3",
+      "resolved": "https://registry.npmjs.org/estree-walker/-/estree-walker-3.0.3.tgz",
+      "integrity": "sha512-7RUKfXgSMMkzt6ZuXmqapOurLGPPfgj6l9uRZ7lRGolvk0y2yocc35LdcxKC5PQZdn2DMqioAQ2NoWcrTKmm6g==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/estree": "^1.0.0"
+      }
+    },
+    "node_modules/expect-type": {
+      "version": "1.2.0",
+      "resolved": "https://registry.npmjs.org/expect-type/-/expect-type-1.2.0.tgz",
+      "integrity": "sha512-80F22aiJ3GLyVnS/B3HzgR6RelZVumzj9jkL0Rhz4h0xYbNW9PjlQz5h3J/SShErbXBc295vseR4/MIbVmUbeA==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "engines": {
+        "node": ">=12.0.0"
+      }
+    },
     "node_modules/fsevents": {
       "version": "2.3.3",
       "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-2.3.3.tgz",
@@ -584,6 +814,30 @@
         "node": "^8.16.0 || ^10.6.0 || >=11.0.0"
       }
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+    "node_modules/loupe": {
+      "version": "3.1.3",
+      "resolved": "https://registry.npmjs.org/loupe/-/loupe-3.1.3.tgz",
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+      "dev": true,
+      "license": "MIT"
+    },
+    "node_modules/magic-string": {
+      "version": "0.30.17",
+      "resolved": "https://registry.npmjs.org/magic-string/-/magic-string-0.30.17.tgz",
+      "integrity": "sha512-sNPKHvyjVf7gyjwS4xGTaW/mCnF8wnjtifKBEhxfZ7E/S8tQ0rssrwGNn6q8JH/ohItJfSQp9mBtQYuTlH5QnA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@jridgewell/sourcemap-codec": "^1.5.0"
+      }
+    },
+    "node_modules/ms": {
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+      "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz",
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+      "dev": true,
+      "license": "MIT"
+    },
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@@ -602,6 +856,23 @@
         "node": "^10 || ^12 || ^13.7 || ^14 || >=15.0.1"
       }
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+    "node_modules/pathe": {
+      "version": "2.0.3",
+      "resolved": "https://registry.npmjs.org/pathe/-/pathe-2.0.3.tgz",
+      "integrity": "sha512-WUjGcAqP1gQacoQe+OBJsFA7Ld4DyXuUIjZ5cc75cLHvJ7dtNsTugphxIADwspS+AraAUePCKrSVtPLFj/F88w==",
+      "dev": true,
+      "license": "MIT"
+    },
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+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/pathval/-/pathval-2.0.0.tgz",
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+      "dev": true,
+      "license": "MIT",
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@@ -664,6 +935,13 @@
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+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/siginfo/-/siginfo-2.0.0.tgz",
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+      "license": "ISC"
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@@ -673,6 +951,64 @@
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+      "resolved": "https://registry.npmjs.org/stackback/-/stackback-0.0.2.tgz",
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+      "dev": true,
+      "license": "MIT"
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+      "resolved": "https://registry.npmjs.org/std-env/-/std-env-3.8.1.tgz",
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+      "dev": true,
+      "license": "MIT"
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+      "version": "2.9.0",
+      "resolved": "https://registry.npmjs.org/tinybench/-/tinybench-2.9.0.tgz",
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+      "dev": true,
+      "license": "MIT"
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+      "resolved": "https://registry.npmjs.org/tinyexec/-/tinyexec-0.3.2.tgz",
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+      "dev": true,
+      "license": "MIT",
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@@ -727,6 +1063,116 @@
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+      },
+      "engines": {
+        "node": "^18.0.0 || ^20.0.0 || >=22.0.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/vitest"
+      },
+      "peerDependencies": {
+        "@edge-runtime/vm": "*",
+        "@types/debug": "^4.1.12",
+        "@types/node": "^18.0.0 || ^20.0.0 || >=22.0.0",
+        "@vitest/browser": "3.0.7",
+        "@vitest/ui": "3.0.7",
+        "happy-dom": "*",
+        "jsdom": "*"
+      },
+      "peerDependenciesMeta": {
+        "@edge-runtime/vm": {
+          "optional": true
+        },
+        "@types/debug": {
+          "optional": true
+        },
+        "@types/node": {
+          "optional": true
+        },
+        "@vitest/browser": {
+          "optional": true
+        },
+        "@vitest/ui": {
+          "optional": true
+        },
+        "happy-dom": {
+          "optional": true
+        },
+        "jsdom": {
+          "optional": true
+        }
+      }
+    },
+    "node_modules/why-is-node-running": {
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/why-is-node-running/-/why-is-node-running-2.3.0.tgz",
+      "integrity": "sha512-hUrmaWBdVDcxvYqnyh09zunKzROWjbZTiNy8dBEjkS7ehEDQibXJ7XvlmtbwuTclUiIyN+CyXQD4Vmko8fNm8w==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "siginfo": "^2.0.0",
+        "stackback": "0.0.2"
+      },
+      "bin": {
+        "why-is-node-running": "cli.js"
+      },
+      "engines": {
+        "node": ">=8"
+      }
     }
   }
 }
diff --git a/package.json b/package.json
index f7e01b20..1d277165 100644
--- a/package.json
+++ b/package.json
@@ -6,10 +6,12 @@
   "scripts": {
     "dev": "vite",
     "build": "vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "vitest"
   },
   "devDependencies": {
-    "vite": "^5.0.0"
+    "vite": "^6.2.0",
+    "vitest": "^3.0.7"
   },
   "dependencies": {
     "delay": "^6.0.0"
diff --git a/src/intro.js b/src/intro.js
index 67ca68e3..f9965a40 100644
--- a/src/intro.js
+++ b/src/intro.js
@@ -12,3 +12,8 @@ export function fizzBuzz(n) {
   if (n % 5 === 0) return 'Buzz';
   return n.toString();
 }
+
+export function testingFactorial(n) {
+  if(n === 0 || n === 1) return 1;
+  if(n > 1) return (n * testingFactorial(n - 1)); 
+}
\ No newline at end of file
diff --git a/tests/intro.test.js b/tests/intro.test.js
new file mode 100644
index 00000000..aa4a5d97
--- /dev/null
+++ b/tests/intro.test.js
@@ -0,0 +1,41 @@
+import { describe, test, it, expect } from "vitest";
+import { sum, max, fizzBuzz, testingFactorial } from "../src/intro";
+
+describe('max', () => {
+    it('should return the first argument if it is greater', () => {
+        expect(max(2, 1)).toBe(2);
+    })
+
+    it('should return the second argument if it is greater', () => {
+        expect(max(1, 2)).toBe(2);
+    })
+
+    it('should return the first argument if the arguments are equal', () => {
+        expect(max(1, 1)).toBe(1);
+    })
+})
+
+describe('fizzBuzz', () => {
+    it('shoulld return FizzBuzz if arg is divisible by 3 and 5', () => {
+        expect(fizzBuzz(15)).toBe('FizzBuzz');
+    })
+    it('shoulld return Fizz if arg is only divisible by 3', () => {
+        expect(fizzBuzz(9)).toBe('Fizz');
+    })
+    it('shoulld return Buzz if arg is only divisible by 5', () => {
+        expect(fizzBuzz(10)).toBe('Buzz');
+    })
+    it('shoulld return arg as a string if it is not divisible by 3 or 5', () => {
+        expect(fizzBuzz(1)).toBe('1');
+    })
+})
+
+describe('testingFactorial', () => {
+    it('should return 1 if arg is 0 or 1', () => {
+        expect(testingFactorial(0)).toBe(1)
+        expect(testingFactorial(1)).toBe(1)
+    })
+    it('should return factorial of n if arg is greater than 1', () => {
+        expect(testingFactorial(3)).toBe(6)
+    }) 
+})
\ No newline at end of file