Add unit test for uncovered regions (#1149)

Co-authored-by: cxworks <cxworks@qq.com>

src/format/scan.rs

@@ -366,8 +366,12 @@ enum CommentState {
 
 #[cfg(test)]
 mod tests {
-    use super::comment_2822;
+    use super::{
+        comment_2822, nanosecond, nanosecond_fixed, short_or_long_month0, short_or_long_weekday,
+        space, timezone_offset_2822,
+    };
     use crate::format::{INVALID, TOO_SHORT};
+    use crate::Weekday;
 
     #[test]
     fn test_rfc2822_comments() {
@@ -402,4 +406,42 @@ mod tests {
             );
         }
     }
+
+    #[test]
+    fn test_timezone_offset_2822() {
+        assert_eq!(timezone_offset_2822("cSt").unwrap(), ("", Some(-21600)));
+        assert_eq!(timezone_offset_2822("pSt").unwrap(), ("", Some(-28800)));
+        assert_eq!(timezone_offset_2822("mSt").unwrap(), ("", Some(-25200)));
+        assert_eq!(timezone_offset_2822("-1551").unwrap(), ("", Some(-57060)));
+        assert_eq!(timezone_offset_2822("Gp").unwrap(), ("", None));
+    }
+
+    #[test]
+    fn test_short_or_long_month0() {
+        assert_eq!(short_or_long_month0("JUn").unwrap(), ("", 5));
+        assert_eq!(short_or_long_month0("mAy").unwrap(), ("", 4));
+        assert_eq!(short_or_long_month0("AuG").unwrap(), ("", 7));
+        assert_eq!(short_or_long_month0("Aprâ").unwrap(), ("â", 3));
+        assert_eq!(short_or_long_month0("JUl").unwrap(), ("", 6));
+        assert_eq!(short_or_long_month0("mAr").unwrap(), ("", 2));
+        assert_eq!(short_or_long_month0("Jan").unwrap(), ("", 0));
+    }
+
+    #[test]
+    fn test_short_or_long_weekday() {
+        assert_eq!(short_or_long_weekday("sAtu").unwrap(), ("u", Weekday::Sat));
+        assert_eq!(short_or_long_weekday("thu").unwrap(), ("", Weekday::Thu));
+    }
+
+    #[test]
+    fn test_nanosecond_fixed() {
+        assert_eq!(nanosecond_fixed("", 0usize).unwrap(), ("", 0));
+        assert!(nanosecond_fixed("", 1usize).is_err());
+    }
+
+    #[test]
+    fn test_nanosecond() {
+        assert_eq!(nanosecond("2Ù").unwrap(), ("Ù", 200000000));
+        assert_eq!(nanosecond("8").unwrap(), ("", 800000000));
+    }
 }