diff --git a/src/types/decimal_floating_point.rs b/src/types/decimal_floating_point.rs
index 8cff64a..9fafba3 100644
--- a/src/types/decimal_floating_point.rs
+++ b/src/types/decimal_floating_point.rs
@@ -32,21 +32,17 @@ impl DecimalFloatingPoint {
     }
 
     pub(crate) fn to_duration(self) -> Duration {
-        let secs = self.0 as u64;
-        let nanos = (self.0.fract() * 1_000_000_000.0) as u32;
-        Duration::new(secs, nanos)
+        Duration::from_secs_f64(self.0)
     }
 
     pub(crate) fn from_duration(duration: Duration) -> Self {
-        let n =
-            (duration.as_secs() as f64) + (f64::from(duration.subsec_nanos()) / 1_000_000_000.0);
-        DecimalFloatingPoint(n)
+        Self(duration.as_secs_f64())
     }
 }
 
 impl From<u32> for DecimalFloatingPoint {
     fn from(f: u32) -> Self {
-        DecimalFloatingPoint(f64::from(f))
+        Self(f64::from(f))
     }
 }
 
@@ -108,5 +104,44 @@ mod tests {
             decimal_floating_point,
             "4.1".parse::<DecimalFloatingPoint>().unwrap()
         );
+
+        assert!("1#".parse::<DecimalFloatingPoint>().is_err());
+    }
+
+    #[test]
+    fn test_new() {
+        assert!(DecimalFloatingPoint::new(std::f64::INFINITY).is_err());
+        assert!(DecimalFloatingPoint::new(-1.0).is_err());
+    }
+
+    #[test]
+    fn test_as_f64() {
+        assert_eq!(DecimalFloatingPoint::new(1.0).unwrap().as_f64(), 1.0);
+    }
+
+    #[test]
+    fn test_from_duration() {
+        assert_eq!(
+            DecimalFloatingPoint::from_duration(Duration::from_nanos(11_234_500_112_345)),
+            DecimalFloatingPoint::new(11234.500112345).unwrap()
+        );
+    }
+
+    #[test]
+    fn test_from() {
+        assert_eq!(
+            DecimalFloatingPoint::from(1u32),
+            DecimalFloatingPoint::new(1.0).unwrap()
+        );
+
+        assert_eq!(
+            DecimalFloatingPoint::from(1 as f64),
+            DecimalFloatingPoint::new(1.0).unwrap()
+        );
+
+        assert_eq!(
+            DecimalFloatingPoint::from(1 as f32),
+            DecimalFloatingPoint::new(1.0).unwrap()
+        );
     }
 }
diff --git a/src/types/decryption_key.rs b/src/types/decryption_key.rs
index 3e4166c..1159461 100644
--- a/src/types/decryption_key.rs
+++ b/src/types/decryption_key.rs
@@ -494,6 +494,29 @@ mod test {
             DecryptionKey::new(EncryptionMethod::Aes128, "https://www.example.com/")
                 .required_version(),
             ProtocolVersion::V1
-        )
+        );
+
+        assert_eq!(
+            DecryptionKey::builder()
+                .method(EncryptionMethod::Aes128)
+                .uri("https://www.example.com/")
+                .key_format(KeyFormat::Identity)
+                .key_format_versions(vec![1, 2, 3])
+                .build()
+                .unwrap()
+                .required_version(),
+            ProtocolVersion::V5
+        );
+
+        assert_eq!(
+            DecryptionKey::builder()
+                .method(EncryptionMethod::Aes128)
+                .uri("https://www.example.com/")
+                .iv([1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7])
+                .build()
+                .unwrap()
+                .required_version(),
+            ProtocolVersion::V2
+        );
     }
 }
diff --git a/src/types/encryption_method.rs b/src/types/encryption_method.rs
index 066dcc0..ac51a4f 100644
--- a/src/types/encryption_method.rs
+++ b/src/types/encryption_method.rs
@@ -104,5 +104,7 @@ mod tests {
             EncryptionMethod::None,
             "NONE".parse::<EncryptionMethod>().unwrap()
         );
+
+        assert!("unknown".parse::<EncryptionMethod>().is_err());
     }
 }
diff --git a/src/types/hdcp_level.rs b/src/types/hdcp_level.rs
index 0b3bbe9..28de702 100644
--- a/src/types/hdcp_level.rs
+++ b/src/types/hdcp_level.rs
@@ -56,5 +56,7 @@ mod tests {
 
         let level = HdcpLevel::None;
         assert_eq!(level, "NONE".parse::<HdcpLevel>().unwrap());
+
+        assert!("unk".parse::<HdcpLevel>().is_err());
     }
 }