diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 463beb8..8cbc82d 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -19,4 +19,4 @@ jobs:
               with:
                   node-version: ${{ matrix.node-version }}
             - run: npm install
-            - run: npm test
+            - run: npm run test
diff --git a/package.json b/package.json
index f241fe6..95446be 100644
--- a/package.json
+++ b/package.json
@@ -19,7 +19,7 @@
 		"node": ">=16"
 	},
 	"scripts": {
-		"test": "xo --env=node && ava && pnpm run build && tsd --typings dist/index.d.ts",
+		"test": "xo --env=node && pnpm run build && mocha -r ts-node/register 'tests/**/*.js'",
 		"build": "del-cli dist && tsc",
 		"prepack": "pnpm run build"
 	},
@@ -31,25 +31,19 @@
 	],
 	"devDependencies": {
 		"@sindresorhus/tsconfig": "^5.0.0",
-		"ava": "^5.3.0",
+		"@types/chai": "^4.3.11",
+		"@types/mocha": "^10.0.6",
+		"chai": "^5.0.0",
 		"del-cli": "^5.1.0",
+		"mocha": "^10.2.0",
 		"ts-node": "^10.9.2",
 		"tsd": "^0.30.4",
-		"tsup": "^8.0.1",
 		"xo": "^0.54.2"
 	},
 	"dependencies": {
 		"@types/node": "^20.11.5",
 		"axios": "^1.6.5"
 	},
-	"ava": {
-		"extensions": {
-			"ts": "module"
-		},
-		"nodeArguments": [
-			"--loader=tsx"
-		]
-	},
 	"prettier": {
 		"trailingComma": "all",
 		"tabWidth": 4,
diff --git a/readme.md b/readme.md
index f752074..03c6449 100644
--- a/readme.md
+++ b/readme.md
@@ -79,7 +79,7 @@ log.Println(message.Code) // 202
 You can run the unit tests for this client from the root directory using the command below:
 
 ```bash
-go test -v
+go tests -v
 ```
 
 ## License
diff --git a/src/cipher-service.test.ts b/src/cipher-service.test.ts
deleted file mode 100644
index 9a78899..0000000
--- a/src/cipher-service.test.ts
+++ /dev/null
@@ -1,5 +0,0 @@
-import test from 'ava';
-
-test('cipherService', t => {
-	t.pass();
-});
diff --git a/src/cipher-service.ts b/src/cipher-service.ts
index 20f944a..a5e3e6b 100644
--- a/src/cipher-service.ts
+++ b/src/cipher-service.ts
@@ -9,22 +9,31 @@ import {Buffer} from 'node:buffer';
 class CipherService {
 	public encrypt(key: string, message: string): string {
 		const iv = randomBytes(16);
-		const cipher = createCipheriv('aes-256-cfb', this.hash(key), iv);
-		return Buffer.from(
-			Buffer.concat([iv, cipher.update(message, 'utf8'), cipher.final()]),
-		).toString('base64');
+		const cipher = createCipheriv(
+			'aes-256-cfb',
+			this.hash(key),
+			iv,
+		).setAutoPadding(false);
+		return Buffer.concat([
+			iv,
+			cipher.update(message, 'utf8'),
+			cipher.final(),
+		]).toString('base64');
 	}
 
 	public decrypt(key: string, message: string): string {
-		const iv = randomBytes(16);
-		const decipher = createDecipheriv('aes-256-cfb', this.hash(key), iv);
-		return Buffer.from(
-			Buffer.concat([
-				iv,
-				decipher.update(message, 'utf8'),
-				decipher.final(),
-			]),
-		).toString('utf8');
+		const cipherBytes = Buffer.from(message, 'base64');
+		const iv = cipherBytes.subarray(0, 16);
+		const decipher = createDecipheriv(
+			'aes-256-cfb',
+			this.hash(key),
+			iv,
+		).setAutoPadding(false);
+
+		return Buffer.concat([
+			decipher.update(cipherBytes.subarray(16, cipherBytes.length)),
+			decipher.final(),
+		]).toString();
 	}
 
 	private hash(value: string): Buffer {
diff --git a/tests/cipher-service.spec.js b/tests/cipher-service.spec.js
new file mode 100644
index 0000000..32c910a
--- /dev/null
+++ b/tests/cipher-service.spec.js
@@ -0,0 +1,19 @@
+import {expect} from 'chai';
+import {describe, it} from 'mocha';
+import CipherService from '../dist/src/cipher-service.js';
+
+describe('CipherService', () => {
+	it('can encrypt and decrypt the same content', () => {
+		// Arrange
+		const key = 'Password123';
+		const message = 'This is a test text message1';
+		const service = new CipherService();
+
+		// Act
+		const cipherText = service.encrypt(key, message);
+		const plainText = service.decrypt(key, cipherText);
+
+		// Assert
+		expect(plainText).to.equal(message);
+	});
+});
diff --git a/tsconfig.json b/tsconfig.json
index b8dfe5b..1f1a3a7 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -2,12 +2,12 @@
 	"extends": "@sindresorhus/tsconfig",
 	"compilerOptions": {
 		"outDir": "dist",
-		"experimentalDecorators": true
+		"experimentalDecorators": true,
+		"esModuleInterop": true
 	},
-	"files": [
-		"index.ts"
-	],
+	"files": ["index.ts"],
 	"ts-node": {
-		"transpileOnly": true
+		"transpileOnly": true,
+		"esm": true
 	}
 }