The Expect API is your Swiss Army knife for MCP testing. Use it to assert everything from simple content checks to complex path efficiency and LLM quality judgments.
Quick reference
TheExpect namespace provides intuitive access to all evaluator factories:
Content namespace
Validate the actual text content returned by your agent:Basic content checks
Advanced content patterns
Tools namespace
Verify tool usage patterns and success rates:Basic tool checks
Tool sequences and patterns
Tool output validation
Performance namespace
Ensure your agent meets performance requirements:Response time and efficiency
Resource usage
Judge namespace
Use LLM judges for nuanced quality evaluation:Simple rubric evaluation
Multi-criteria evaluation
Custom judge configuration
Path namespace
Enforce optimal execution paths:Golden path enforcement
Flexible path checking
Combining assertions
Create comprehensive test scenarios by combining multiple assertions:Best practices
Use descriptive names: Always provide a
name parameter for your assertions. This makes debugging much easier when tests fail.See also
Complete Assertions Reference
Every available assertion with examples
Custom Evaluators
Build your own domain-specific evaluators