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Overview

Expressions let you inject dynamic values into step fields without writing full code. They are evaluated at runtime and can reference:
  • env.*: environment variables from your selected Environment
  • vars.*: test variables produced by earlier steps (e.g., Extract Text)
  • random.*: built‑in random data generators (email, name, uuid, etc.)
  • Utility functions: one‑line helpers for dates, encoding, hashing, and random operations
Use expressions inside double braces {{ ... }}. You can mix text with expressions, chain methods, and apply simple JavaScript. Expressions in step fields

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When to use

  • Build URLs from environment values and previous step outputs
  • Fill forms with dynamic or random data
  • Verify text or URLs that contain variable parts
  • Drive conditional logic using values computed on the fly

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Autocomplete and sources

In supported fields, typing {{ opens an autocomplete with tabs for Env, Vars, Random, and Utils. Select an item to insert it automatically. Autocomplete with Env/Vars/Random tabs
  • Env (env.*): Read‑only key‑values defined in the selected Environment
  • Vars (vars.*): Values saved by earlier steps in the same test case
  • Random (random.*): Utilities like email(), firstName(), uuid(), number(min,max)
  • Utils: One‑line utility functions for dates, encoding, hashing, and random operations

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Syntax

  • Wrap in braces: {{ ... }}
  • Mix with static text: Hello {{ vars.firstName }}!
  • Chain methods: {{ vars.email.trim().toLowerCase() }}
  • Build paths: {{ env.API_BASE }}/users/{{ vars.userId }}
  • Generate data: {{ random.email() }}

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Common examples

  • URL from env and vars: {{ env.APP_URL }}/account/{{ vars.accountId }}
  • Normalizing a value: {{ vars.username.strip().lower() }}
  • Array operations: {{ [t.strip() for t in env.TAGS.split(',')] }}
  • Fallbacks: {{ vars.displayName or env.DEFAULT_NAME }}
  • Compose multiple parts: Hello {{ vars.firstName }} {{ vars.lastName }}!

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Utility functions

Utility functions provide one‑line helpers for common operations. Access them via autocomplete by typing {{ utils. or find them in the Utils tab. These functions are available globally in expressions, so you can call them directly without a prefix.

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Date and time

Use date and time utilities to work with timestamps, dates, and time calculations:
  • now(): Current date and time {{ format_date(now(), '%Y-%m-%d') }}
  • today(): Current date {{ today() }}
  • timestamp(): Unix timestamp {{ timestamp() }}
  • timedelta(days=...): Time difference for date arithmetic {{ format_date(today() + timedelta(days=7), '%Y-%m-%d') }}
  • format_date(date_obj, fmt='%d/%m/%Y'): Format a date object {{ format_date(now(), '%Y-%m-%d %H:%M:%S') }}

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String encoding and crypto

Encode, decode, hash, and transform strings:
  • uuid(): Generate a random UUID {{ uuid() }}
  • md5(text): Generate MD5 hash {{ md5(vars.password) }}
  • sha256(text): Generate SHA256 hash {{ sha256(vars.apiKey + env.SECRET) }}
  • hmac_sha256(key, msg): Generate HMAC signature {{ hmac_sha256(env.API_SECRET, vars.message) }}
  • b64encode(text): Base64 encode {{ b64encode(vars.credentials) }}
  • b64decode(text): Base64 decode {{ b64decode(env.ENCODED_TOKEN) }}
  • urlencode(text): URL encode {{ urlencode(vars.searchQuery) }}
  • urldecode(text): URL decode {{ urldecode(vars.encodedParam) }}
  • slugify(text): Convert text to URL‑friendly slug {{ slugify(vars.pageTitle) }}

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Math and random

Generate random numbers and select random items:
  • randint(min, max): Random integer in range {{ randint(1, 100) }}
  • choice(list): Pick random item from list {{ choice(['option1', 'option2', 'option3']) }}
  • sample(list, k): Pick k random items from list {{ sample(['a', 'b', 'c', 'd'], 2) }}

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Where it works

  • Navigate (URL)
  • Fill Text (value)
  • Verify Text / Verify URL (expected value)
  • Select Option (value)
  • Start Condition (expression)
  • Other fields that support text input in the editor

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Expressions in locators

You can use expressions in element locators.
  • String locators (e.g., CSS, text engine): If a locator includes {{ ... }}, it’s evaluated at runtime and passed to page.locator(...).
    • Example:
    text={{ vars.buttonText }}
    This becomes a dynamic string at runtime, supporting mixes like: 
    [data-cy="btn-{{ vars.action }}-{{ env.SEGMENT }}"]
  • Functional locators (Playwright API style): When your step stores a functional locator (e.g., getByRole, getByTestId, locator(...) chains), expressions are supported only inside quoted string literals. The rest of the call remains code-safe.
    • Example:
    getByRole('button', { name: '{{ vars.submitLabel }}' })
    At runtime, only the quoted string literal is evaluated, keeping the function call intact.

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Notes and safeguards

  • Expressions are evaluated at runtime using the same sources (env, vars, random).
  • For functional locators, only quoted string literals are transformed. Non‑string parts (objects, function names) are preserved to avoid code injection and keep type safety.
  • Prefer concise expressions; move complex logic to a prior step (e.g., Capture Value or Run Python) and reference via vars.*.

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Best practices

  • Ensure the variable exists before use (the step that creates it must run earlier)
  • Keep expressions concise; move complex logic to a “Run Python” step when needed
  • Do not attempt to assign to env.* (read‑only)
  • Prefer strip()/lower() for robust comparisons in verifications

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How to use in Run Python

In the Run Python step you do not use {{ }}. The following are directly available:
  • env.* (read‑only)
  • vars.*
  • random.*
  • Utility functions (same as in expressions: now(), uuid(), md5(), etc.)
Use this step for multi‑line logic, loops, mappings, or to set new variables for later steps. Run JavaScript globals

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Troubleshooting

  • Variable not found: confirm the producing step ran earlier and saved a variable
  • Quote handling: prefer {{ ... }} without additional quotes; the editor handles string composition
  • Curly braces: make sure both {{ and }} are present and balanced