POST with a template file

Generate unique data per request from a JSON template. Useful for testing APIs that require varied payloads — different user IDs, amounts, session tokens.

Save your template file anywhere in your project — pass the path with -T. A common convention is to keep templates in a templates/ directory at the project root.

1. Create a template file

Save this as templates/order.json:

{
  "userId": "{{user_id}}",
  "amount": "{{amount}}",
  "_loadtest_metadata_templates": {
    "user_id": {
      "type": "string",
      "details": {
        "choice": ["user-001", "user-002", "user-003", "user-004", "user-005"]
      }
    },
    "amount": {
      "type": "float",
      "min": 1,
      "max": 500,
      "details": {
        "decimals": 2
      }
    }
  }
}

Each request gets a freshly generated userId and amount. The _loadtest_metadata_templates block is stripped before sending.

2. Run with the template

lmn run -H https://api.example.com/orders \
  -M post \
  -T ./templates/order.json

Placeholder types

Type	What it generates
string with choice	Randomly picks from the list
string with exact	Fixed-length alphanumeric string
string with min/max	Random-length alphanumeric string
float with min/max	Random float in range
float with exact	Always emits the same float value
object with composition	Nested object composed from other placeholders

Static values (same across all requests)

Add :once to generate a value once and reuse it across all requests:

{
  "sessionId": "{{session_id:once}}",
  "item": "{{item_name}}"
}

Inject environment variables

Use {{ENV:VAR_NAME}} to pull a value from the environment — no template definition needed:

{
  "apiKey": "{{ENV:API_KEY}}",
  "userId": "{{user_id}}"
}

If the variable is not set, lmn exits immediately with an error before any requests fire.

See Template Placeholders for the full reference.