11-generate-tests

Generate Tests

Agent generates a test suite for untested code, using branching to try multiple testing strategies and pick the best.

Prerequisites

• sandcaster CLI installed (from monorepo: cd apps/cli && bun link)

Setup

export E2B_API_KEY="your-key"       # https://e2b.dev/dashboard
export OPENAI_API_KEY="your-key"    # https://platform.openai.com/api-keys

Run

sandcaster -f sample-code/utils.ts "Write tests for the uploaded utils.ts"

What Happens

Sandcaster spawns 3 parallel branches, each independently writing tests for the utility module. An LLM judge evaluates coverage, edge-case handling, and readability, then selects the best test suite.

Configuration

See sandcaster.json for the full configuration. Key settings:

• model: gpt5 (OpenAI gpt-5.4 — cost-efficient default)
• branching: 3 parallel branches with LLM judge evaluation
• allowedTools: Read, Glob, Grep, Bash (can run tests in sandbox)

Troubleshooting

• "No LLM provider API key found": Set OPENAI_API_KEY in your environment
• "E2B_API_KEY not set": Get a key at https://e2b.dev/dashboard
• Model not available: Replace gpt5 with sonnet or haiku in sandcaster.json