more test learn that borrowing means free trait gets

src/engine.rs

@@ -0,0 +1,33 @@
+pub trait InputEngine {
+   fn get(&self) -> String;
+}
+
+struct InputEngineStdin {}
+
+impl InputEngine for InputEngineStdin {
+   fn get(&self) -> String {
+      return "hello world".to_string();
+   }
+}
+
+#[cfg(test)]
+mod test {
+   use super::*;
+
+   struct InputEngineTest {}
+   impl InputEngine for InputEngineTest {
+      fn get(&self) -> String {
+         return "hello world".to_string();
+      }
+   }
+
+   #[test]
+   fn test_input_engine_impl() {
+      let input_engine_test = InputEngineTest{};
+      _test_input_engine_impl(&input_engine_test);
+   }
+
+   fn _test_input_engine_impl(engine: &dyn InputEngine) {
+      assert_eq!("hello world".to_string(), engine.get());
+   }
+}

src/main.rs

@@ -1,4 +1,5 @@
 pub mod config;
+pub mod engine;
 
 fn main() {
    let cfg = config::build_config();