| name | cairo-snforge-troubleshooting |
| description | Diagnose and fix common snforge test errors including Sierra compilation failures, cost computation cycles, and version mismatches; use when tests fail with cryptic errors even though `scarb build` succeeds. |
Cairo snforge Troubleshooting
Overview
Guide debugging snforge test failures, particularly Sierra compilation errors that occur after successful Cairo compilation.
Quick Use
- Read
references/common-errors.md before diagnosing.
- Check
Scarb.toml settings first - enable-gas = false causes many issues.
- Verify toolchain version compatibility (snforge, universal-sierra-compiler, Cairo).
- Generic implementations need proper trait bounds.
Response Checklist
- If error mentions "cycle during cost computation": check
enable-gas setting.
- If error mentions "universal-sierra-compiler": check version compatibility.
- If generic code fails: ensure
+Drop<T>, +Copy<T> bounds and struct derives.
- If
scarb build passes but scarb test fails: issue is test-specific compilation.
Common Error Patterns
"unexpected cycle during cost computation"
Cause: enable-gas = false in [cairo] section of Scarb.toml
Fix: Remove enable-gas = false or set to true
"Error while compiling Sierra"
Cause: Version mismatch between Cairo and universal-sierra-compiler
Fix: Run snfoundryup to update toolchain
Generic impl compilation issues
Cause: Missing trait bounds on generic implementations
Fix: Add +Drop<T>, +Copy<T> to impl and #[derive(Drop, Copy)] to structs
Example Requests
- "My tests fail with 'unexpected cycle during cost computation'"
- "snforge test fails but scarb build works"
- "universal-sierra-compiler error after Cairo upgrade"
