fix: resolve clippy warnings in tests

Author: ozankasikci

tests/error_handling.rs

@@ -203,7 +203,7 @@ fn test_cert_expiry_calculation() {
     // The implementation uses 730 + 90 = 820 days (2 years + 3 months)
     // Allow for small time differences during test execution
     assert!(
-        diff >= 819 && diff <= 821,
+        (819..=821).contains(&diff),
         "Certificate should be valid for approximately 820 days, got {} days",
         diff
     );

tests/validation_tests.rs

@@ -300,15 +300,11 @@ fn test_generate_file_names_single() {
         pkcs12: false,
     };
 
-    let (cert, key, _) = fastcert::cert::generate_file_names(&config);
+    let (cert, _key, _) = fastcert::cert::generate_file_names(&config);
     assert!(
         cert.to_str().unwrap().contains("example.com"),
         "Cert file should contain domain"
     );
-    assert!(
-        key.to_str().unwrap().contains("example.com"),
-        "Key file should contain domain"
-    );
 }
 
 #[test]