diff --git a/src/substrate_app.test.ts b/src/substrate_app.test.ts
new file mode 100644
index 0000000..722ca1f
--- /dev/null
+++ b/src/substrate_app.test.ts
@@ -0,0 +1,40 @@
+/** ******************************************************************************
+ *  (c) 2019 - 2022 Zondax AG
+ *  (c) 2016-2017 Ledger
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ ******************************************************************************* */
+import { MockTransport } from '@ledgerhq/hw-transport-mocker'
+import { PolkadotGenericApp } from './generic_app'
+
+describe('API', function () {
+  test('SignRaw - Valid', () => {
+    const responseBuffer = Buffer.concat([
+      Buffer.from([0, 1, 2, 3, 0]), // Version information
+      Buffer.from([0x90, 0x00]), // Status code for no errors (0x9000)
+    ])
+
+    const transport = new MockTransport(responseBuffer)
+    const app = new PolkadotGenericApp(transport)
+
+    const mockBlob = Buffer.from('0x00')
+
+    const result = await app.signRaw('m/0', mockBlob)
+
+    expect(result.signature).toBe('0x00')
+  })
+
+  test('SignRaw - Error', () => {
+    expect(false).toBeFalsy()
+  })
+})