Strip ns precision from rate limiting tests

Linux has ns precision when fetching the current timestamp, most other
platforms only have us precision. PG *always* only stores us precision,
so roundtripping `Utc::now()` through the database may change it on
Linux. Since we're checking for exact equality in these tests, we need
to normalize the value ahead of time.

Author: sgrif

src/publish_rate_limit.rs

@@ -110,7 +110,7 @@ mod tests {
     #[test]
     fn take_token_with_no_bucket_creates_new_one() -> CargoResult<()> {
         let conn = pg_connection();
-        let now = Utc::now().naive_utc();
+        let now = now();
 
         let rate = PublishRateLimit {
             rate: Duration::from_secs(1),
@@ -141,7 +141,7 @@ mod tests {
     #[test]
     fn take_token_with_existing_bucket_modifies_existing_bucket() -> CargoResult<()> {
         let conn = pg_connection();
-        let now = Utc::now().naive_utc();
+        let now = now();
 
         let rate = PublishRateLimit {
             rate: Duration::from_secs(1),
@@ -161,7 +161,7 @@ mod tests {
     #[test]
     fn take_token_after_delay_refills() -> CargoResult<()> {
         let conn = pg_connection();
-        let now = Utc::now().naive_utc();
+        let now = now();
 
         let rate = PublishRateLimit {
             rate: Duration::from_secs(1),
@@ -206,7 +206,7 @@ mod tests {
     #[test]
     fn last_refill_always_advanced_by_multiple_of_rate() -> CargoResult<()> {
         let conn = pg_connection();
-        let now = Utc::now().naive_utc();
+        let now = now();
 
         let rate = PublishRateLimit {
             rate: Duration::from_millis(100),
@@ -227,7 +227,7 @@ mod tests {
     #[test]
     fn zero_tokens_returned_when_user_has_no_tokens_left() -> CargoResult<()> {
         let conn = pg_connection();
-        let now = Utc::now().naive_utc();
+        let now = now();
 
         let rate = PublishRateLimit {
             rate: Duration::from_secs(1),
@@ -250,7 +250,7 @@ mod tests {
     #[test]
     fn a_user_with_no_tokens_gets_a_token_after_exactly_rate() -> CargoResult<()> {
         let conn = pg_connection();
-        let now = Utc::now().naive_utc();
+        let now = now();
 
         let rate = PublishRateLimit {
             rate: Duration::from_secs(1),
@@ -272,7 +272,7 @@ mod tests {
     #[test]
     fn tokens_never_refill_past_burst() -> CargoResult<()> {
         let conn = pg_connection();
-        let now = Utc::now().naive_utc();
+        let now = now();
 
         let rate = PublishRateLimit {
             rate: Duration::from_secs(1),
@@ -294,7 +294,7 @@ mod tests {
     #[test]
     fn override_is_used_instead_of_global_burst_if_present() -> CargoResult<()> {
         let conn = pg_connection();
-        let now = Utc::now().naive_utc();
+        let now = now();
 
         let rate = PublishRateLimit {
             rate: Duration::from_secs(1),
@@ -343,4 +343,14 @@ mod tests {
             .get_result(conn)
             .map_err(Into::into)
     }
+
+    /// Strips ns precision from `Utc::now`. PostgreSQL only has microsecond
+    /// precision, but some platforms (notably Linux) provide nanosecond
+    /// precision, meaning that round tripping through the database would
+    /// change the value.
+    fn now() -> NaiveDateTime {
+        let now = Utc::now().naive_utc();
+        let nanos = now.timestamp_subsec_nanos();
+        now - chrono::Duration::nanoseconds(nanos as i64)
+    }
 }