WIP: Add testing

Author: chansuke

tests/ui/unwrap.rs

@@ -1,3 +1,5 @@
+// compile-flags: --test
+
 #![warn(clippy::unwrap_used)]
 
 fn unwrap_option() {
@@ -10,7 +12,13 @@ fn unwrap_result() {
     let _ = res.unwrap();
 }
 
-fn main() {
-    unwrap_option();
-    unwrap_result();
+#[cfg(test)]
+mod test {
+    #[test]
+    fn test_flag() {
+        let opt = Some(0);
+        let _ = opt.unwrap();
+    }
 }
+
+fn main() {}

tests/ui/unwrap.stderr

@@ -1,5 +1,5 @@
 error: used `unwrap()` on `an Option` value
-  --> $DIR/unwrap.rs:5:13
+  --> $DIR/unwrap.rs:7:13
    |
 LL |     let _ = opt.unwrap();
    |             ^^^^^^^^^^^^
@@ -8,12 +8,20 @@ LL |     let _ = opt.unwrap();
    = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
 
 error: used `unwrap()` on `a Result` value
-  --> $DIR/unwrap.rs:10:13
+  --> $DIR/unwrap.rs:12:13
    |
 LL |     let _ = res.unwrap();
    |             ^^^^^^^^^^^^
    |
    = help: if you don't want to handle the `Err` case gracefully, consider using `expect()` to provide a better panic message
 
-error: aborting due to 2 previous errors
+error: used `unwrap()` on `an Option` value
+  --> $DIR/unwrap.rs:20:17
+   |
+LL |         let _ = opt.unwrap();
+   |                 ^^^^^^^^^^^^
+   |
+   = help: if you don't want to handle the `None` case gracefully, consider using `expect()` to provide a better panic message
+
+error: aborting due to 3 previous errors