tor-llcrypto: Add test case for RsaIdentity formatting

I'm going to change the code that does this, so add a test first
to check the output doesn't change.

At some point we should have more RSA tests.

crates/tor-llcrypto/tests/misc.rs

@@ -37,6 +37,25 @@ fn test_ed25519_identity() {
     assert_eq!(ex3.as_bytes(), &example_key[..]);
 }
 
+#[test]
+fn test_rsa_formatting() {
+    use ll::pk::rsa::RsaIdentity;
+
+    let id = hex::decode("5696ab38cb3852afa476a5c07b2d4788963d5567").unwrap();
+    let id = RsaIdentity::from_bytes(&id).unwrap();
+
+    assert_eq!(
+        format!("<<{}>>", id),
+        "<<$5696ab38cb3852afa476a5c07b2d4788963d5567>>"
+    );
+    assert_eq!(
+        format!("{:?}", id),
+        "RsaIdentity { $5696ab38cb3852afa476a5c07b2d4788963d5567 }"
+    );
+}
+
+// TODO: Proper tests for RSA keys
+
 #[test]
 fn batch_verify() {
     use ll::pk::ed25519::*;