test(runtime-config): Add some tests to make sure data is cached

rust_snuba/src/runtime_config.rs

@@ -40,6 +40,8 @@ pub fn get_str_config(key: &str) -> Result<Option<String>, Error> {
 
 #[cfg(test)]
 mod tests {
+    use std::thread;
+
     use super::*;
 
     #[test]
@@ -48,4 +50,32 @@ mod tests {
         let config = get_str_config("test");
         assert_eq!(config.unwrap(), None);
     }
+
+    #[test]
+    fn test_runtime_config_retrieves_from_cache_within_deadline() {
+        CONFIG.write().insert(
+            "key".to_string(),
+            (
+                Some("value".to_string()),
+                Deadline::new(Duration::from_secs(10)),
+            ),
+        );
+        let config = get_str_config("key");
+        assert_eq!(config.unwrap(), Some("value".to_string()));
+        CONFIG.write().clear();
+    }
+
+    #[test]
+    fn test_runtime_config_invalidates_cache_outside_deadline() {
+        CONFIG.write().insert(
+            "key".to_string(),
+            (
+                Some("value".to_string()),
+                Deadline::new(Duration::from_secs(1)),
+            ),
+        );
+        thread::sleep(Duration::from_secs(60));
+        let config = get_str_config("key");
+        assert_eq!(config.unwrap(), None);
+    }
 }