Fix serde error message and add tests

Author: dtolnay

Cargo.toml

@@ -15,3 +15,4 @@ unreachable = "0.1"
 
 [dev-dependencies]
 stainless = "0.1"
+serde_test = "0.9"

src/lib.rs

@@ -601,6 +601,13 @@ mod impl_serde {
     use num_traits::Float;
     use std::f64;
 
+    #[cfg(test)]
+    extern crate serde_test;
+    #[cfg(test)]
+    use self::serde_test::{Token, assert_tokens, assert_de_tokens_error};
+    #[cfg(test)]
+    use self::serde_test::Error::Message;
+
     impl<T: Float + Serialize> Serialize for OrderedFloat<T> {
         fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
             self.0.serialize(s)
@@ -621,10 +628,29 @@ mod impl_serde {
 
     impl<T: Float + Deserialize> Deserialize for NotNaN<T> {
         fn deserialize<D: Deserializer>(d: D) -> Result<Self, D::Error> {
-            T::deserialize(d).and_then(|v| {
-                NotNaN::new(v)
-                    .map_err(|_| <D::Error as Error>::invalid_value(Unexpected::Float(f64::NAN), &"NaN"))
+            let float = T::deserialize(d)?;
+            NotNaN::new(float).map_err(|_| {
+                Error::invalid_value(Unexpected::Float(f64::NAN), &"float (but not NaN)")
             })
         }
     }
+
+    #[test]
+    fn test_ordered_float() {
+        let float = OrderedFloat(1.0f64);
+        assert_tokens(&float, &[Token::F64(1.0)]);
+    }
+
+    #[test]
+    fn test_not_nan() {
+        let float = NotNaN(1.0f64);
+        assert_tokens(&float, &[Token::F64(1.0)]);
+    }
+
+    #[test]
+    fn test_fail_on_nan() {
+        assert_de_tokens_error::<NotNaN<f64>>(
+            &[Token::F64(f64::NAN)],
+            Message("invalid value: floating point `NaN`, expected float (but not NaN)".into()));
+    }
 }