Test Key::list

Adds a live-against-the-device test which ensures keys can be
successfully listed.

src/policy.rs

@@ -35,6 +35,7 @@ impl From<PinPolicy> for u8 {
 impl PinPolicy {
     /// Writes the `PinPolicy` in the format the YubiKey expects during key generation or
     /// importation.
+    #[cfg(feature = "untested")]
     pub(crate) fn write(self, buf: &mut [u8]) -> usize {
         match self {
             PinPolicy::Default => 0,
@@ -84,6 +85,7 @@ impl From<TouchPolicy> for u8 {
 impl TouchPolicy {
     /// Writes the `TouchPolicy` in the format the YubiKey expects during key generation
     /// or importation.
+    #[cfg(feature = "untested")]
     pub(crate) fn write(self, buf: &mut [u8]) -> usize {
         match self {
             TouchPolicy::Default => 0,