postman-test-script-generator

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SKILL.md (first lines)

# Postman Test Script Writer

Writes and embeds **Postman JavaScript test scripts** — both `prerequest` and `test` scripts —
into collection requests. Works from an existing collection JSON or a plain description.

---

## Postman Scripting Basics

Postman scripts use the `pm` object and run in a sandboxed JS environment (no Node.js builtins).

### Key APIs

```javascript
// --- Assertions ---
pm.test("description", () => { pm.expect(...).to... });

// --- Response access ---
pm.response.code           // HTTP status code (number)
pm.response.json()         // Parse body as JSON
pm.response.text()         // Body as string
pm.response.headers.get("Content-Type")
pm.response.responseTime   // ms (number)

// --- Variables ---
pm.environment.set("key", value);
pm.environment.get("key");
pm.collectionVariables.set("key", value);
pm.collectionVariables.get("key");
pm.variables.get("key");   // resolves: local > data > env > collection > global

// --- Pre-request ---
pm.request.headers.add({ key: "X-Header", value: "val" });
```

---

## Step 1 — Understand What to Test

Identify the user's intent across these categories:

| Category | Examples |
|---|---|
| **Status assertion** | "should return 200", "expect 201 on create" |
| **Schema/field check** | "response must have `id` and `name`", "check nested field" |
| **Value assertion** | "user.email equals input", "count > 0" |
| **Response time** | "must respond under 500ms" |
| **Chaining** | "save token from login response for next request" |
| **Dynamic pre-request** | "generate timestamp before request", "set random ID" |
| **Error handling** | "if 401, log warning", "check error message format" |

---

## Step 2 — Write the Scripts

### Status Code
```javascript
pm.test("Status is 200", () => {
  pm.response.to.have.status(200);
});
```

### JSON Field Existence
```javascript
pm.test("Response has required fields", () => {
  const body = pm.response.json();
  pm.expect(body).to.have.property("id");
  pm.expect(body).to.have.property("name");
});
```

### Field Type & Value
```javascript
pm.test("ID is a positive number", () => {
  const body = pm.response.json();
  pm.expect(body.id).to.be.a("number").and.to.be.above(0);
});
```

### Array Response
```javascript
pm.test("Returns a non-empty array", () => {
  const body = pm.response.json();
  pm.expect(body).to.be.an("array").with.length.above(0);
});
```

### Response Time
```javascript
pm.test("Response time under 500ms", () => {
  pm.expect(pm.response.responseTime).to.be.below(500);
});
```

### Chaining — Save token after login
```javascript
// In Tests tab of login request:
pm.test("Login successful", () => {
  pm.response.to.have.status(200);
  const { access_token } = pm.response.json();
  pm.environment.set("token", access_token);
});
```

### Pre-request — Dynamic value
```javascript
// In Pre-request Script tab:
pm.collectionVariables.set("timestamp", Date.now());
pm.collectionVariables.set("random_id", Math.floor(Math.random() * 10000));
```

### Schema Validation (using Ajv-style via tv4)
```javascript
const schema = {
  type: "object",
  required: ["id", "email"],
  properties: {
    id: { type: "number" },
    email: { type: "string" }

From LambdaTest/agent-skills, MIT.

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