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JavaScript steps execute code as part of a test. async/await is supported. Return values are passed to downstream steps and must be JSON-serializable. 
const res = await axios.post("https://api.example.com/login", {
  email: env.USERNAME,
  password: env.PASSWORD,
});

setVariable("SESSION_TOKEN", res.data.token);
return res.status;

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Execution contexts

ContextWhen to useAccess
Node sandboxDefault. API calls, data prep, secret rotation, DB queries.Momentic globals (see below)
Browser pageEnable Execute in browser. DOM queries, local storage.window, document, page globals
Browser steps don’t have access to the Node sandbox globals.

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{{ }} templating

Any string input on any step can contain {{ expression }}. Expressions evaluate at runtime and are interpolated into the value. 
- id: 488b...
  type: PRESET_ACTION
  command:
    id: a2ba...
    type: TYPE
    target:
      type: description
      elementDescriptor: Email field
    value: "{{ env.USERNAME }}@gmail.com"
Don’t use {{}} inside JavaScript step source. Variables are already in scope as env.VARIABLE_NAME.

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Momentic utilities

Provided by the Momentic runtime.

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env

Read-only map of the current environment’s variables. See Variables for how variables are resolved. 
const res = await axios.get("https://api.example.com/me", {
  headers: { Authorization: `Bearer ${env.API_TOKEN}` },
});

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setVariable(name, value)

Write a variable scoped to the current test run. Downstream steps can read it via {{ name }} in any string input, or via env.name inside JavaScript. 
const res = await axios.post("https://api.example.com/login", {
  email: env.USERNAME,
  password: env.PASSWORD,
});

setVariable("SESSION_TOKEN", res.data.token);

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email

Send and fetch email. See Email for inbox setup. 
// fetch the latest verification email
const msg = await email.fetchLatest({
  inbox: "[email protected]",
  timeout: 30,
});
const code = msg.text.match(/\d{6}/)[0];
setVariable("VERIFICATION_CODE", code);

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sms

Send and fetch SMS. See SMS for number setup. 
const msg = await sms.fetchLatest({
  to: "+15551234567",
  timeout: 60,
});
setVariable("OTP", msg.body.match(/\d{6}/)[0]);

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ai.generate({ input })

Call an LLM inside a step. Useful for generating dynamic test data or reasoning about a response. See Agentic testing. 
const { text } = await ai.generate({
  input: `Return a realistic fake US phone number as digits only.`,
});
setVariable("PHONE", text);

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extractCookiesFromResponse(response)

Convert a fetch / axios response’s Set-Cookie headers into an array of Playwright-compatible cookies. Useful for bootstrapping an authenticated browser context. 
const res = await fetch("https://api.example.com/login", {
  method: "POST",
  body: JSON.stringify({ email: env.USERNAME, password: env.PASSWORD }),
});

const cookies = await extractCookiesFromResponse(res);
setVariable("AUTH_COOKIES", cookies);

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mock

Only available in mock handler steps on mocked routes. Exposes the intercepted Request and the upstream Response. 
// stub the /pricing response but forward everything else
if (mock.request.url.endsWith("/pricing")) {
  return new Response(JSON.stringify({ plan: "enterprise" }), {
    status: 200,
    headers: { "content-type": "application/json" },
  });
}
return mock.response;

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Libraries

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axios

HTTP client. See axios docs. 
const { data } = await axios.get("https://api.example.com/status");
assert.equal(data.ok, true);

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assert

Node’s built-in assertions. See Node docs. 
assert.equal(res.status, 200);
assert.deepStrictEqual(res.data, { success: true });

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faker

Generate realistic fake data. See Faker docs. 
const email = faker.internet.email();
const name = faker.person.fullName();
setVariable("NEW_USER_EMAIL", email);
setVariable("NEW_USER_NAME", name);

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moment

Parse and format dates. See Moment docs. 
// pick a date 30 days from now, formatted for a date input
setVariable("FUTURE_DATE", moment().add(30, "days").format("YYYY-MM-DD"));

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pg

Postgres client. See node-postgres docs. 
const client = new pg.Client({ connectionString: env.DATABASE_URL });
await client.connect();
const { rows } = await client.query(
  "SELECT id FROM users WHERE email = $1 LIMIT 1",
  [env.TEST_EMAIL],
);
await client.end();
setVariable("USER_ID", rows[0].id);

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OTPAuth

Generate TOTP codes for 2FA tests. See otpauth docs. 
const totp = new OTPAuth.TOTP({ secret: env.TOTP_SECRET });
setVariable("OTP_CODE", totp.generate());

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child_process

Spawn subprocesses. See Node docs. 
const { execSync } = child_process;
const branch = execSync("git rev-parse --abbrev-ref HEAD").toString().trim();
setVariable("GIT_BRANCH", branch);

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Octokit + createAppAuth

Authenticated GitHub API access. See Octokit docs and auth-app docs. 
const octokit = new Octokit({
  authStrategy: createAppAuth,
  auth: {
    appId: env.GITHUB_APP_ID,
    privateKey: env.GITHUB_APP_PRIVATE_KEY,
    installationId: env.GITHUB_INSTALLATION_ID,
  },
});

const { data: pr } = await octokit.rest.pulls.get({
  owner: "momentic-ai",
  repo: "examples",
  pull_number: 42,
});
setVariable("PR_STATE", pr.state);