Check specific error codes in the tests

If possible, check specific error codes instead of `is_err()`.  This
makes the code more readable and catches bugs resulting in the wrong
error code.  Also, using the assert_*_err and assert_ok macros yields
error messages containing the expected and the actual value.

To be able to use these macros with the `get_password_safe` method, we
also have to implement `Debug` for `PasswordSafe` and `Device`.

2 files changed, 2 insertions, 1 deletions

diff --git a/src/device.rs b/src/device.rs
index 1cf9da9..16064c3 100644
--- a/src/device.rs
+++ b/src/device.rs
@@ -286,7 +286,7 @@ pub struct StorageStatus {
 ///
 /// This trait provides the commands that can be executed without authentication and that are
 /// present on all supported Nitrokey devices.
-pub trait Device: Authenticate + GetPasswordSafe + GenerateOtp {
+pub trait Device: Authenticate + GetPasswordSafe + GenerateOtp + fmt::Debug {
     /// Returns the model of the connected Nitrokey device.
     ///
     /// # Example
diff --git a/src/pws.rs b/src/pws.rs
index 47965d7..a21527c 100644
--- a/src/pws.rs
+++ b/src/pws.rs
@@ -52,6 +52,7 @@ pub const SLOT_COUNT: u8 = 16;
 /// [`get_password_safe`]: trait.GetPasswordSafe.html#method.get_password_safe
 /// [`lock`]: trait.Device.html#method.lock
 /// [`GetPasswordSafe`]: trait.GetPasswordSafe.html
+#[derive(Debug)]
 pub struct PasswordSafe<'a> {
     _device: &'a dyn Device,
 }