Monitoring as Code: Learn more about the API Check Construct.

​
API Check Test Structure

import { ApiCheck, AssertionBuilder, Frequency } from 'checkly/constructs'

new ApiCheck('user-api-health', {
  name: 'User API Health Check',
  frequency: Frequency.EVERY_5M,
  request: {
    method: 'GET',
    url: 'https://api.example.com/v1/users/health',
    headers: {
      'Authorization': 'Bearer {{API_TOKEN}}'
    },
    assertions: [
      AssertionBuilder.statusCode().equals(200),
      AssertionBuilder.responseTime().lessThan(2000),
      AssertionBuilder.jsonBody('$.status').equals('healthy')
    ]
  }
})

​
Request Configuration

​
HTTP Methods

Support for all standard HTTP methods:
  • GET: Retrieve data from endpoints
  • POST: Create resources or submit data
  • PUT: Update existing resources
  • PATCH: Partial resource updates
  • DELETE: Remove resources
  • HEAD: Check resource existence without body
  • OPTIONS: Discover allowed methods

​
Request Components

# Example API check configuration
Method: POST
URL: https://api.example.com/v1/users
Headers:
  Content-Type: "application/json"
  Authorization: "Bearer {{api_token}}"
Body: |
  {
    "name": "John Doe",
    "email": "john@example.com"
  }

​
Authentication Support

  • Bearer Token: JWT and OAuth token authentication
  • Basic Auth: Username/password authentication
  • API Keys: Custom header or query parameter authentication
  • Custom Headers: Flexible authentication patterns

​
Response Validation

​
Status Code Assertions

Validate HTTP response codes: 
// Status code validation
expect(response.status).to.equal(200)
expect(response.status).to.be.oneOf([200, 201, 202])
expect(response.status).to.be.below(400)

​
Content Validation

Validate response content and structure: 
// JSON response validation
const data = JSON.parse(response.body)
expect(data.success).to.be.true
expect(data.user.id).to.be.a('number')
expect(data.user.email).to.include('@')

// Text content validation
expect(response.body).to.include('success')
expect(response.body).to.not.include('error')

​
Header Validation

Check response headers: 
// Header validation
expect(response.headers['content-type']).to.include('application/json')
expect(response.headers['cache-control']).to.exist
expect(response.headers['x-rate-limit-remaining']).to.be.above(0)

​
JSON Schema Validation

Validate complex response structures: 
{
  "type": "object",
  "properties": {
    "id": {"type": "integer"},
    "name": {"type": "string"},
    "email": {"type": "string", "format": "email"},
    "created_at": {"type": "string", "format": "date-time"}
  },
  "required": ["id", "name", "email"]
}

​
Advanced Features

​
Environment Variables

Use variables for dynamic content: 
// Reference environment variables
const baseUrl = process.env.API_BASE_URL
const apiKey = process.env.API_KEY

// Dynamic request configuration
const userId = Math.floor(Math.random() * 1000)

​
Request Chaining

Use previous responses in subsequent requests: 
// Setup script - create test user
const userResponse = await fetch('https://api.example.com/users', {
  method: 'POST',
  body: JSON.stringify({
    name: 'Test User',
    email: `test+${Date.now()}@example.com`
  })
})
const userData = await userResponse.json()
process.env.TEST_USER_ID = userData.id

// Main request uses created user ID
// URL: https://api.example.com/users/{{TEST_USER_ID}}/profile

​
GraphQL Support

Monitor GraphQL APIs: 
// GraphQL query example
const query = `
  query GetUser($id: ID!) {
    user(id: $id) {
      id
      name
      email
      profile {
        avatar
        bio
      }
    }
  }
`

// Request body
{
  "query": query,
  "variables": {
    "id": "123"
  }
}