Introduce UnwrapError trait to simplify error testing

For testing purposes it is beneficial to be able to check for expected
errors with the least amount of boiler plate code possible. This change
attempts to be a first step into this direction. It introduces a
test-only trait that can be used to directly unwrap a specific error
from a Result<T, crate::error::Error>.

2 files changed, 22 insertions, 11 deletions

diff --git a/nitrocli/src/tests/mod.rs b/nitrocli/src/tests/mod.rs
index 474b43c..cb0d09e 100644
--- a/nitrocli/src/tests/mod.rs
+++ b/nitrocli/src/tests/mod.rs
@@ -17,6 +17,8 @@
 // * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
 // *************************************************************************
 
+use std::fmt;
+
 use nitrokey_test::test as test_device;
 
 // TODO: This is a hack to make the nitrokey-test crate work across
@@ -63,6 +65,24 @@ impl IntoArg for nitrokey::DeviceWrapper {
   }
 }
 
+/// A trait simplifying checking for expected errors.
+pub trait UnwrapError {
+  /// Unwrap an Error::Error variant.
+  fn unwrap_str_err(self) -> String;
+}
+
+impl<T> UnwrapError for crate::Result<T>
+where
+  T: fmt::Debug,
+{
+  fn unwrap_str_err(self) -> String {
+    match self.unwrap_err() {
+      crate::Error::Error(err) => err,
+      err => panic!("Unexpected error variant found: {:?}", err),
+    }
+  }
+}
+
 mod nitrocli {
   use super::*;
 
diff --git a/nitrocli/src/tests/status.rs b/nitrocli/src/tests/status.rs
index e8a4f51..838ebc9 100644
--- a/nitrocli/src/tests/status.rs
+++ b/nitrocli/src/tests/status.rs
@@ -33,17 +33,8 @@ fn not_found_raw() {
 
 #[test_device]
 fn not_found() {
-  match nitrocli::handle(NO_DEV, &["status"]) {
-    Ok(_) => assert!(false),
-    Err(err) => {
-      // Unfortunately we can't directly compare against the error
-      // because not all of the variants implement PartialEq.
-      match err {
-        crate::Error::Error(x) => assert_eq!(x, "Nitrokey device not found".to_string()),
-        _ => assert!(false, err),
-      }
-    }
-  }
+  let res = nitrocli::handle(NO_DEV, &["status"]);
+  assert_eq!(res.unwrap_str_err(), "Nitrokey device not found");
 }
 
 #[test_device]