test: add integration test

Author: bruzina

README.md

@@ -44,6 +44,7 @@ Tests:
 
 ```shell
 ./test_unit
+../tests/test_integration.sh
 ```
 
 Cleanup:

tests/test_integration.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+output=$(./cpp-cli)
+if [[ "$output" == "Hello world" ]]; then
+    echo "[PASS] Output correct."
+else
+    echo "[FAIL] Output = $output"
+    exit 1
+fi