cairo-snforge-troubleshooting

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"