rt: add test for runtime panic (#159)

Co-authored-by: ollie-etl <Oliver Bunting@etlsystems.com>

src/runtime/mod.rs

@@ -130,3 +130,23 @@ impl Drop for Runtime {
         CONTEXT.with(|rc| rc.unset_driver())
     }
 }
+
+#[cfg(test)]
+mod test {
+
+    use super::*;
+    use crate::builder;
+
+    #[test]
+    fn block_on() {
+        let rt = Runtime::new(&builder()).unwrap();
+        rt.block_on(async move { () });
+    }
+
+    #[test]
+    fn block_on_twice() {
+        let rt = Runtime::new(&builder()).unwrap();
+        rt.block_on(async move { () });
+        rt.block_on(async move { () });
+    }
+}