Why APIs Eliminates More Candidates Than They Expect

// Tests tab of: POST {{baseUrl}}/orders

pm.test("Order created", function () {
    pm.response.to.have.status(201);
});

const body = pm.response.json();

pm.test("Response has an order id", function () {
    pm.expect(body.id).to.be.a("number");
});

// Save for the next requests in the collection
pm.environment.set("orderId", body.id);
pm.environment.set("orderTotal", body.total);

// Request: GET {{baseUrl}}/orders/{{orderId}}
// Tests tab:

pm.test("Fetched the same order", function () {
    pm.response.to.have.status(200);
    const body = pm.response.json();
    pm.expect(body.id).to.eql(Number(pm.environment.get("orderId")));
    pm.expect(body.total).to.eql(Number(pm.environment.get("orderTotal")));
});

pm.test("New order starts as PLACED", function () {
    pm.expect(pm.response.json().status).to.eql("PLACED");
});

// Request: POST {{baseUrl}}/orders
// Body: { "qty": 2 }      (productId deliberately missing)

pm.test("Rejected with 400", function () {
    pm.response.to.have.status(400);
});

pm.test("Error names the missing field", function () {
    const body = pm.response.json();
    pm.expect(JSON.stringify(body)).to.include("productId");
});

pm.test("No order id returned", function () {
    pm.expect(pm.response.json()).to.not.have.property("id");
});

qty,expectedStatus
0,400
1,201
100,201
101,400
-1,400

// Save as qty-boundaries.csv and run the collection with
// the Collection Runner (or Newman with -d), using a body:
// { "productId": 42, "qty": {{qty}} }
// Note: {{qty}} is unquoted so it is sent as a number.

// Tests tab:
pm.test("qty " + pm.iterationData.get("qty") + " handled",
  function () {
    pm.response.to.have.status(
        Number(pm.iterationData.get("expectedStatus")));
});

// Command line:
// newman run orders.postman_collection.json \
//   -e test.postman_environment.json -d qty-boundaries.csv

{
  "type": "object",
  "required": ["id", "productId", "qty", "total", "status"],
  "properties": {
    "id":        { "type": "integer" },
    "productId": { "type": "integer" },
    "qty":       { "type": "integer", "minimum": 1, "maximum": 100 },
    "total":     { "type": "number",  "minimum": 0 },
    "status":    { "type": "string",
                   "enum": ["PLACED", "SHIPPED", "CANCELLED"] },
    "couponCode":{ "type": ["string", "null"] }
  },
  "additionalProperties": false
}

// Tests tab of: GET {{baseUrl}}/orders/{{orderId}}

const orderSchema = {
  type: "object",
  required: ["id", "productId", "qty", "total", "status"],
  properties: {
    id:        { type: "integer" },
    productId: { type: "integer" },
    qty:       { type: "integer", minimum: 1, maximum: 100 },
    total:     { type: "number", minimum: 0 },
    status:    { type: "string",
                 enum: ["PLACED", "SHIPPED", "CANCELLED"] },
    couponCode:{ type: ["string", "null"] }
  },
  additionalProperties: false
};

pm.test("Order matches schema", function () {
    pm.response.to.have.jsonSchema(orderSchema);
});

FOLDER 1: Auth
  01 POST /login             -> save token

FOLDER 2: Happy path chain
  02 POST /orders            -> save orderId, total
  03 GET /orders/{{orderId}} -> compare, schema check
  04 PATCH /orders/{{orderId}} (qty: 3)
  05 GET /orders/{{orderId}} -> qty is 3, total updated
  06 DELETE /orders/{{orderId}}
  07 GET /orders/{{orderId}} -> 404 or CANCELLED

FOLDER 3: Negative
  08 POST /orders, missing productId -> 400
  09 POST /orders, qty as string     -> 400/422
  10 GET /orders/1 with no token     -> 401
  11 Boundary run with CSV           -> mixed

# Install Newman (Postman's command-line runner)
npm install -g newman newman-reporter-htmlextra

# Run with an environment and an HTML report
newman run orders.postman_collection.json \
  -e test.postman_environment.json \
  -r cli,htmlextra \
  --reporter-htmlextra-export reports/orders.html

# Exit code is non-zero if any test fails,
# so a CI job (Jenkins, GitHub Actions, GitLab CI)
# marks the build as failed automatically.

# Keep secrets out of the exported environment file;
# pass them with --env-var "password=$API_PASSWORD"

Practise this two-minute explanation:

"My collection has three folders. Auth logs in and
saves the token. The happy path creates an order,
saves its ID and reuses it to fetch, update and delete,
checking the schema on each GET.

The negative folder covers a missing field, a wrong
type, no token, and boundary values for quantity from
a CSV file.

It runs in CI with Newman, and the build fails if any
test fails. Secrets come from CI variables."

In Uncodemy mock rounds, this is usually followed by:
'What would you add next?' Have one answer ready.