validate_me

Python CLI tool for validating API JSON responses against configurable rules. Supports nested JSON, array indexing, and QA/Postman workflows.

Why I built this

While learning QA Engineering and API Testing with Postman, I wanted to get my hands super dirty and build a project that forced me to learn the ins and outs of API response validation with Python. To this end, I built a Python CLI validator that checks an API response in Postman against prescribed, configurable rules.

Features

The tool allows the user to:

• Validate required fields
• Validate expected data types
• Support nested JSON via dot-path syntax
• Support array/list indexing (movies[0].title)
• Generate structured JSON validation reports
• CLI workflow for API/Postman testing

Example JSON response

{
    "userId": 1,
    "id": 1,
    "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
    "body": "quia et suscipit\nsuscipit recusandae consequuntur expedita et cum\nreprehenderit molestiae ut ut quas totam\nnostrum rerum est autem sunt rem eveniet architecto"
}

Example JSON rules file

{
  "required_keys": [
    "userId",
    "id",
    "title",
    "body"
  ],
  "expected_types": {
    "userId": "integer",
    "id": "integer",
    "title": "string",
    "body": "string"
  }
}

Example Output

Passing example:

{
  "overall_passed": true,
  "all_checks": [
    {
      "path": "userId",
      "check_type": "required",
      "passed": true
    },
    {
      "path": "id",
      "check_type": "required",
      "passed": true
    },
    {
      "path": "title",
      "check_type": "required",
      "passed": true
    },
    {
      "path": "body",
      "check_type": "required",
      "passed": true
    },
    {
      "path": "userId",
      "check_type": "type",
      "expected_type": "integer",
      "passed": true
    },
    {
      "path": "id",
      "check_type": "type",
      "expected_type": "integer",
      "passed": true
    },
    {
      "path": "title",
      "check_type": "type",
      "expected_type": "string",
      "passed": true
    },
    {
      "path": "body",
      "check_type": "type",
      "expected_type": "string",
      "passed": true
    }
  ]
}

Failing example:

{
  "overall_passed": false,
  "all_checks": [
    {
      "path": "userId",
      "check_type": "required",
      "passed": true
    },
    {
      "path": "id",
      "check_type": "required",
      "passed": true
    },
    {
      "path": "title",
      "check_type": "required",
      "passed": true
    },
    {
      "path": "body",
      "check_type": "required",
      "passed": false,
      "reason": "missing key"
    },
    {
      "path": "userId",
      "check_type": "type",
      "expected_type": "integer",
      "passed": false,
      "reason": "wrong type",
      "actual_type": "str"
    },
    {
      "path": "id",
      "check_type": "type",
      "expected_type": "integer",
      "passed": true
    },
    {
      "path": "title",
      "check_type": "type",
      "expected_type": "string",
      "passed": true
    },
    {
      "path": "body",
      "check_type": "type",
      "expected_type": "string",
      "passed": false,
      "reason": "missing key"
    }
  ]
}

Lessons Learned

Building this API validation tool forced me to learn many key skills, most notably:

• Nested JSON traversal
• List index validation
• CLI argument parsing with argparse
• JSON schema logic
• Debugging validation edge cases