ReddRadar
Agent skill
frontmcp-testing
Use when you want to write tests, run tests, add e2e tests, improve test coverage, test a tool, test a resource, or learn how to test any FrontMCP component. The skill for ALL testing needs.
Install this agent skill to your Project
npx add-skill https://github.com/agentfront/frontmcp/tree/main/libs/skills/catalog/frontmcp-testing
Metadata
Additional technical details for this skill
SKILL.md
FrontMCP Testing Router
Entry point for testing FrontMCP applications. This skill helps you navigate testing strategies across component types and find the right patterns for unit, integration, and E2E tests.
When to Use This Skill
Must Use
- Setting up testing infrastructure for a new FrontMCP project
- Deciding how to test a specific component type (tool, resource, prompt, agent)
- Planning a testing strategy that covers unit, E2E, and coverage requirements
Recommended
- Looking up testing patterns for a component type you haven't tested before
- Understanding the relationship between unit tests, E2E tests, and coverage thresholds
- Troubleshooting test failures or coverage gaps
Skip When
- You need detailed Jest configuration and test harness setup (go directly to
setup-testing) - You need to build components, not test them (see
frontmcp-development) - You need to deploy, not test (see
frontmcp-deployment)
Decision: Use this skill for testing strategy and routing. Use
setup-testingfor hands-on Jest configuration and test writing.
Scenario Routing Table
| Scenario | Skill / Section | Description |
|---|---|---|
| Set up Jest, coverage, and test harness | setup-testing |
Full Jest config, test utilities, and coverage thresholds |
| Write unit tests for a tool | setup-testing (Unit Testing) |
Mock DI, validate input/output, test error paths |
| Write unit tests for a resource | setup-testing (Unit Testing) |
Test URI resolution, template params, read results |
| Write unit tests for a prompt | setup-testing (Unit Testing) |
Test argument handling, message generation |
| Write E2E protocol-level tests | setup-testing (E2E Testing) |
Real MCP client/server, full protocol flow |
| Test authenticated endpoints | test-auth |
E2E with OAuth tokens, session validation, role-based access |
| Test deployment builds | setup-testing + deploy-to-* |
Smoke tests against built output |
| Test browser builds | test-browser-build |
Testing browser builds |
| Test CLI binary builds | test-cli-binary |
Testing CLI binary builds |
| Test with the direct API client | test-direct-client |
Testing with the direct API client |
| Write E2E test handler patterns | test-e2e-handler |
E2E test handler patterns |
| Unit test individual tools | test-tool-unit |
Unit testing individual tools |
Testing Strategy by Component Type
| Component | Unit Test Focus | E2E Test Focus | Key Assertions |
|---|---|---|---|
| Tool | Input validation, execute logic, error paths, DI mocking | tools/call via MCP client |
Output matches schema, errors return MCP codes |
| Resource | URI resolution, read content, template param handling | resources/read via MCP client |
Content type correct, URI patterns resolve |
| Prompt | Argument validation, message generation, multi-turn | prompts/get via MCP client |
Messages match expected structure |
| Agent | LLM config, tool selection, handoff logic | Agent loop via MCP client | Tools called in order, result synthesized |
| Provider | Lifecycle hooks, factory output, singleton behavior | Indirectly via tool/resource tests | Instance reuse, cleanup on scope disposal |
| Job | Progress tracking, retry logic, attempt counting | Job execution via test harness | Progress events emitted, retries respected |
| Workflow | Step dependencies, conditions, input mapping functions | Workflow run via test harness | Steps execute in order, conditions evaluated, continueOnError respected |
| Skill | Instruction loading (inline/file/url), tool validation | Skill discovery via MCP/HTTP | Instructions resolve, tool refs validated per toolValidation mode |
| Plugin | Context extensions, provider registration, hook firing | Indirectly via tool tests | Extensions available on this, hooks fire at correct stages |
Cross-Cutting Testing Patterns
| Pattern | Rule |
|---|---|
| File naming | Always .spec.ts (not .test.ts); E2E uses .e2e.spec.ts |
| File organization | Split E2E tests by app/feature: e2e/calc.e2e.spec.ts, e2e/ecommerce.e2e.spec.ts. Never put all tests in a single server.e2e.spec.ts |
| Test runner | Use frontmcp test (not jest --config ...). It auto-generates the correct Jest/SWC config |
| Coverage threshold | 95%+ across statements, branches, functions, lines |
| Test descriptions | Plain English, no prefixes like "PT-001"; describe behavior not implementation |
| Mocking | Mock providers via DI token replacement, never mock the framework |
| httpMock scope | httpMock intercepts HTTP in the test process only, NOT in the MCP server subprocess. Do not use httpMock to intercept server-to-API calls — those happen in the child process. Use httpMock for verifying client-to-server request shapes or mocking external APIs called from the test itself |
| Error testing | Assert instanceof specific error class AND MCP error code |
| Async | Always await async operations; use expect(...).rejects.toThrow() for async errors |
Common Patterns
| Pattern | Correct | Incorrect | Why |
|---|---|---|---|
| Test file location | fetch-weather.tool.spec.ts next to source |
__tests__/fetch-weather.test.ts |
Co-location with .spec.ts extension matches FrontMCP conventions |
| DI mocking | Replace token with mock via scope.register(TOKEN, mockImpl) |
jest.mock('../provider') module mock |
DI mocking is cleaner, type-safe, and tests the real integration path |
| Error assertions | expect(err).toBeInstanceOf(ResourceNotFoundError) |
expect(err.message).toContain('not found') |
Class checks are stable; message strings are fragile |
| E2E transport | Use @frontmcp/testing MCP client with real server |
HTTP requests with fetch |
The test client handles protocol details (session, framing) |
| Coverage gaps | Investigate uncovered branches, add targeted tests | Add istanbul ignore comments |
Coverage gaps often hide real bugs; ignoring them defeats the purpose |
Verification Checklist
Infrastructure
- Jest configured with
@frontmcp/testingpreset - Coverage thresholds set to 95% in jest.config
- Test files use
.spec.tsextension throughout
Unit Tests
- Each tool has unit tests covering happy path, validation errors, and DI failures
- Each resource has unit tests covering URI resolution and read content
- Provider lifecycle (init, dispose) tested where applicable
E2E Tests
- At least one E2E test exercises full MCP protocol flow (connect, list, call, disconnect)
- Authenticated E2E tests use proper test tokens (not mocked auth)
- E2E tests clean up state after execution
CI Integration
- Tests run in CI pipeline on every PR
- Coverage report published and enforced
- Failing tests block merge
Troubleshooting
| Problem | Cause | Solution |
|---|---|---|
| Jest not finding test files | Wrong file extension (.test.ts instead of .spec.ts) |
Rename to .spec.ts; check testMatch in jest.config |
| Coverage below 95% | Untested error paths or conditional branches | Run frontmcp test --coverage and inspect uncovered lines in the report |
| E2E test timeout | Server startup too slow or port conflict | Increase Jest timeout; use random port allocation |
| DI resolution fails in tests | Provider not registered in test scope | Register mock providers before creating the test context |
| Istanbul shows 0% on async methods | TypeScript source-map mismatch with Istanbul | Known issue with some TS compilation settings; verify coverage with actual test output |
Reference
- Testing Documentation
- Related skills:
setup-testing,create-tool,create-resource,create-prompt,configure-auth
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