Component Patterns

Purpose

Provide verification strategies for different component types. This skill defines how to test real behavior for CLIs, servers, parsers, processes, databases, and external APIs.

When to Use

Load this skill when:

• Generating verification scripts via bulwark-verify skill
• Determining how to test a specific component type
• Implementing test-audit Step 7 rewrites

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Component Type Detection

Analyze the code to determine component type based on these indicators:

Indicators	Component Type	Pattern Reference
Imports child_process, has spawn/exec/execSync	Process Spawner	references/pattern-process-spawner.md
Imports http/https/express/fastify/koa, has listen()	HTTP Server	references/pattern-http-server.md
Imports fs, reads/parses files, has parse functions	File Parser	references/pattern-file-parser.md
Has CLI argument parsing (process.argv, yargs, commander, argparse)	CLI Command	references/pattern-cli-command.md
Imports database driver (pg, mysql, mongoose, sqlite, prisma)	Database	references/pattern-database.md
Makes outbound HTTP calls (fetch, axios, got, requests)	External API	references/pattern-external-api.md

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Pattern Reference Files

Each pattern reference contains:

• Strategy: High-level approach for testing the component type
• Templates: Ready-to-use verification script templates in Bash, Node/Jest, and Python/pytest
• Placeholders: Variables to substitute with component-specific values

Available Patterns

Pattern	File	Languages
CLI Command	references/pattern-cli-command.md	Bash, Node, Python
HTTP Server	references/pattern-http-server.md	Bash, Node (supertest), Python
File Parser	references/pattern-file-parser.md	Bash, Node, Python
Process Spawner	references/pattern-process-spawner.md	Bash, Node
Database	references/pattern-database.md	Node, Python, Bash (SQLite)
External API	references/pattern-external-api.md	Node (MSW), Python (responses)

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Usage Instructions

Step 1: Detect Component Type

Analyze the target component code using the detection table above.

Step 2: Load Pattern Reference

Read the appropriate pattern file from references/:

Read skills/component-patterns/references/pattern-{type}.md

Step 3: Select Template

Choose the template that matches the project language:

• Node projects (package.json present): Use Node/Jest template
• Python projects (pyproject.toml or setup.py present): Use Python/pytest template
• Generic/Other: Use Bash template

Step 4: Substitute Placeholders

Replace all {placeholder} values with component-specific information:

Common Placeholders	Description
{component_name}	Name of the component being tested
{component_path}	Import path to the module
{port}	Network port (for servers/processes)
{expected_value}	Expected output to verify

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Quick Reference: Component to Pattern

Component Type	Verification Strategy	Key Assertion
CLI Command	Spawn, capture stdout/stderr	Exit code + output text
HTTP Server	Start, HTTP request, verify response	Status code + response body
File Parser	Create input, parse, check structure	Parsed fields + values
Process Spawner	Spawn, check port/pid, verify behavior	Process alive + responds
Database	Setup DB, execute ops, query state	Records exist/modified
External API	MSW intercept, real fetch, check result	Response data matches

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Key Principle: Real Verification

All patterns follow the same principle: verify observable output, not mock calls.

Anti-Pattern	Real Pattern
expect(spawn).toHaveBeenCalled()	expect(await checkPort(8080)).toBe(true)
expect(fs.writeFile).toHaveBeenCalled()	expect(fs.existsSync(path)).toBe(true)
expect(fetch).toHaveBeenCalledWith(url)	const resp = await fetch(url); expect(resp.status).toBe(200)
expect(db.save).toHaveBeenCalled()	const found = await db.find(id); expect(found).toBeDefined()

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Diagnostic Output

Write diagnostic output to logs/diagnostics/component-patterns-{YYYYMMDD-HHMMSS}.yaml:

skill: component-patterns
timestamp: {ISO-8601}
diagnostics:
  component_type_detected: cli|http|file-parser|process|database|api
  pattern_applied: "CLI Command Verification"
  template_language: bash|node|python
  files_analyzed: 1
  completion_status: success