Assertions

Assertions let you validate HTTP responses and browser page state — status codes, response bodies, headers, latency, page URLs, extracted text, and more. They use a fluent API that reads naturally:

Assert(state["my-request"].status).equals(200)
Assert(state["my-request"].body["name"]).not.isEmpty()

API request assertion subjects

You can assert on four properties of any HTTP request node:

Status code

Assert(state["req"].status).equals(200)
Assert(state["req"].status).greaterThanOrEqual(200)
Assert(state["req"].status).lessThan(300)

Response body

Access nested properties with bracket notation. Use .at(index) for array elements. For steps with response_format: NoContent (e.g. 204 No Content), there is no body — assert only on state["req"].status (e.g. .equals(204)).

// Simple property
Assert(state["req"].body["message"]).equals("ok")

// Nested property
Assert(state["req"].body["data"]["user"]["name"]).equals("Alice")

// Array element
Assert(state["req"].body["items"].at(0)["id"]).isDefined()

// Check the whole body
Assert(state["req"].body["data"]).not.isEmpty()

Headers

Assert(state["req"].headers["content-type"]).contains("application/json")
Assert(state["req"].headers["x-request-id"]).isDefined()

Latency

Latency is measured in milliseconds:

Assert(state["req"].latency).lessThan(2000)
Assert(state["req"].latency).lessThanOrEqual(500)

Browser assertion subjects

Browser nodes expose different properties than API request nodes. See Browser Monitors for full details.

Page URL

Assert(state["browser_node"].page.url).contains("/dashboard")
Assert(state["browser_node"].page.url).startsWith("https://")

Page title

Assert(state["browser_node"].page.title).equals("Dashboard")
Assert(state["browser_node"].page.title).contains("App")

Duration

Total time for all browser steps, in milliseconds:

Assert(state["browser_node"].duration).lessThan(5000)

Console errors

JavaScript errors captured from the browser console:

Assert(state["browser_node"].console.errors).isEmpty()

Extracted text

Values captured by extractText() steps:

Assert(state["browser_node"].extracts["heading"]).equals("Welcome")
Assert(state["browser_node"].extracts["price"]).contains("$")

Predicates

Comparison

Method	Description
`.equals(value)`	Exact equality
`.greaterThan(n)`	Greater than
`.lessThan(n)`	Less than
`.greaterThanOrEqual(n)`	Greater than or equal
`.lessThanOrEqual(n)`	Less than or equal

String

Method	Description
`.contains(str)`	Contains substring
`.startsWith(str)`	Starts with prefix
`.endsWith(str)`	Ends with suffix

Existence

Method	Description
`.isNull()`	Value is null
`.isDefined()`	Value is not null
`.isEmpty()`	Value is empty (empty string, array, or object)
`.isTrue()`	Value is true
`.isFalse()`	Value is false

Negation

Prefix any predicate with .not to negate it:

Assert(state["req"].body["error"]).not.isDefined()
Assert(state["req"].status).not.equals(500)
Assert(state["req"].body["name"]).not.isEmpty()
Assert(state["req"].body["items"]).not.isNull()

Using with the sequential builder

The sequential builder provides a callback with a type-safe state proxy:

builder
  .request("users", { ... })
  .assert((state) => [
    Assert(state["users"].status).equals(200),
    Assert(state["users"].body["count"]).greaterThan(0),
  ])

The state proxy only exposes nodes that have been defined above the assertion, giving you compile-time autocomplete.

Using with the graph builder

With the graph builder, create a state proxy manually using createStateProxy:

import { createStateProxy, Assert, Assertion } from "@griffin-app/griffin";

const state = createStateProxy(["get-users", "create-user"]);

builder.addNode("validate", Assertion([
  Assert(state["get-users"].status).equals(200),
  Assert(state["create-user"].status).equals(201),
]))

Multiple assertions

You can add multiple assertion nodes to validate different parts of your flow:

builder
  .request("create", { ... })
  .assert((state) => [
    Assert(state["create"].status).equals(201),
  ])
  .request("read", { ... })
  .assert((state) => [
    Assert(state["read"].status).equals(200),
    Assert(state["read"].body["name"]).equals("Test"),
  ])

A monitor run is marked as failed if any assertion in any assertion node fails.

Getting Started

Concepts

Writing Monitors

Platform

Griffin Hub

Griffin Cloud

Command Line

API request assertion subjects

Status code

Response body

Headers

Latency

Browser assertion subjects

Page URL

Page title

Duration

Console errors

Extracted text

Predicates

Comparison

String

Existence

Negation

Using with the sequential builder

Using with the graph builder

Multiple assertions

​API request assertion subjects

​Status code

​Response body

​Headers

​Latency

​Browser assertion subjects

​Page URL

​Page title

​Duration

​Console errors

​Extracted text

​Predicates

​Comparison

​String

​Existence

​Negation

​Using with the sequential builder

​Using with the graph builder

​Multiple assertions

API request assertion subjects

Status code

Response body

Headers

Latency

Browser assertion subjects

Page URL

Page title

Duration

Console errors

Extracted text

Predicates

Comparison

String

Existence

Negation

Using with the sequential builder

Using with the graph builder

Multiple assertions