Add another test file from #43

tests/testdata/cpp/simple/variables.cpp

@@ -0,0 +1,11 @@
+#include <iostream>
+
+int main() {
+    std::cout << "Hello world!" << std::endl;
+    int a = 1;
+    ++a;
+    int& b = a;
+    ++a;
+    std::cout << "a: " << a << " b: " << b << std::endl;
+    return 0;
+}