diff --git a/src/liblog/directive.rs b/src/liblog/directive.rs
index a93cf4c1568..d1db0ec89a1 100644
--- a/src/liblog/directive.rs
+++ b/src/liblog/directive.rs
@@ -100,7 +100,6 @@ mod tests {
     #[test]
     fn parse_logging_spec_valid() {
         let (dirs, filter) = parse_logging_spec("crate1::mod1=1,crate1::mod2,crate2=4");
-        let dirs = dirs.as_slice();
         assert_eq!(dirs.len(), 3);
         assert_eq!(dirs[0].name, Some("crate1::mod1".to_string()));
         assert_eq!(dirs[0].level, 1);
@@ -117,7 +116,6 @@ mod tests {
     fn parse_logging_spec_invalid_crate() {
         // test parse_logging_spec with multiple = in specification
         let (dirs, filter) = parse_logging_spec("crate1::mod1=1=2,crate2=4");
-        let dirs = dirs.as_slice();
         assert_eq!(dirs.len(), 1);
         assert_eq!(dirs[0].name, Some("crate2".to_string()));
         assert_eq!(dirs[0].level, 4);
@@ -128,7 +126,6 @@ mod tests {
     fn parse_logging_spec_invalid_log_level() {
         // test parse_logging_spec with 'noNumber' as log level
         let (dirs, filter) = parse_logging_spec("crate1::mod1=noNumber,crate2=4");
-        let dirs = dirs.as_slice();
         assert_eq!(dirs.len(), 1);
         assert_eq!(dirs[0].name, Some("crate2".to_string()));
         assert_eq!(dirs[0].level, 4);
@@ -139,7 +136,6 @@ mod tests {
     fn parse_logging_spec_string_log_level() {
         // test parse_logging_spec with 'warn' as log level
         let (dirs, filter) = parse_logging_spec("crate1::mod1=wrong,crate2=warn");
-        let dirs = dirs.as_slice();
         assert_eq!(dirs.len(), 1);
         assert_eq!(dirs[0].name, Some("crate2".to_string()));
         assert_eq!(dirs[0].level, ::WARN);
@@ -150,7 +146,6 @@ mod tests {
     fn parse_logging_spec_empty_log_level() {
         // test parse_logging_spec with '' as log level
         let (dirs, filter) = parse_logging_spec("crate1::mod1=wrong,crate2=");
-        let dirs = dirs.as_slice();
         assert_eq!(dirs.len(), 1);
         assert_eq!(dirs[0].name, Some("crate2".to_string()));
         assert_eq!(dirs[0].level, ::MAX_LOG_LEVEL);
@@ -161,7 +156,6 @@ mod tests {
     fn parse_logging_spec_global() {
         // test parse_logging_spec with no crate
         let (dirs, filter) = parse_logging_spec("warn,crate2=4");
-        let dirs = dirs.as_slice();
         assert_eq!(dirs.len(), 2);
         assert_eq!(dirs[0].name, None);
         assert_eq!(dirs[0].level, 2);
@@ -173,7 +167,6 @@ mod tests {
     #[test]
     fn parse_logging_spec_valid_filter() {
         let (dirs, filter) = parse_logging_spec("crate1::mod1=1,crate1::mod2,crate2=4/abc");
-        let dirs = dirs.as_slice();
         assert_eq!(dirs.len(), 3);
         assert_eq!(dirs[0].name, Some("crate1::mod1".to_string()));
         assert_eq!(dirs[0].level, 1);
@@ -183,26 +176,24 @@ mod tests {
 
         assert_eq!(dirs[2].name, Some("crate2".to_string()));
         assert_eq!(dirs[2].level, 4);
-        assert!(filter.is_some() && filter.unwrap().to_string().as_slice() == "abc");
+        assert!(filter.is_some() && filter.unwrap().to_string() == "abc");
     }
 
     #[test]
     fn parse_logging_spec_invalid_crate_filter() {
         let (dirs, filter) = parse_logging_spec("crate1::mod1=1=2,crate2=4/a.c");
-        let dirs = dirs.as_slice();
         assert_eq!(dirs.len(), 1);
         assert_eq!(dirs[0].name, Some("crate2".to_string()));
         assert_eq!(dirs[0].level, 4);
-        assert!(filter.is_some() && filter.unwrap().to_string().as_slice() == "a.c");
+        assert!(filter.is_some() && filter.unwrap().to_string() == "a.c");
     }
 
     #[test]
     fn parse_logging_spec_empty_with_filter() {
         let (dirs, filter) = parse_logging_spec("crate1/a*c");
-        let dirs = dirs.as_slice();
         assert_eq!(dirs.len(), 1);
         assert_eq!(dirs[0].name, Some("crate1".to_string()));
         assert_eq!(dirs[0].level, ::MAX_LOG_LEVEL);
-        assert!(filter.is_some() && filter.unwrap().to_string().as_slice() == "a*c");
+        assert!(filter.is_some() && filter.unwrap().to_string() == "a*c");
     }
 }