Faker Extension

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The WireMock Faker Extension uses the Data Faker library to generate random, realistic fake data for use in WireMock response templates. This is particularly useful for creating test data that looks authentic without hardcoding values.

Installation

The Faker extension is packaged separately from the core WireMock library. Add it to your project using Maven or Gradle:

Maven

<dependency>
    <groupId>org.wiremock.extensions</groupId>
    <artifactId>wiremock-faker-extension</artifactId>
    <version>0.2.0</version>
</dependency>

Gradle

dependencies {
    implementation 'org.wiremock.extensions:wiremock-faker-extension-standalone:0.2.0'
}

note

The extension includes net.datafaker:datafaker as a transitive dependency. If you encounter build conflicts with this library, you may need to exclude it from other dependencies in your project.

Registering the extension

To use the Faker extension, you need to register it with your WireMock server:

Java

import org.wiremock.extensions.RandomExtension;

WireMockServer wireMockServer = new WireMockServer(
    wireMockConfig()
        .extensions(RandomExtension.class)
);

Standalone

When running WireMock standalone, register the extension via the command line:

java -jar wiremock-standalone.jar --extensions org.wiremock.extensions.RandomExtension

Using the random helper

Once the extension is registered, you can use the random Handlebars helper in your response templates. The helper takes a single parameter specifying the type of fake data to generate, in the format Category.Key.

Basic usage

JSON

{
  "request": {
    "method": "GET",
    "url": "/api/user"
  },
  "response": {
    "status": 200,
    "jsonBody": {
      "firstName": "{{random 'Name.first_name'}}",
      "lastName": "{{random 'Name.last_name'}}",
      "email": "{{random 'Internet.email_address'}}"
    },
    "transformers": ["response-template"]
  }
}

Java

stubFor(get(urlEqualTo("/api/user"))
    .willReturn(aResponse()
        .withStatus(200)
        .withHeader("Content-Type", "application/json")
        .withBody("{\n" +
            "  \"firstName\": \"{{random 'Name.first_name'}}\",\n" +
            "  \"lastName\": \"{{random 'Name.last_name'}}\",\n" +
            "  \"email\": \"{{random 'Internet.email_address'}}\"\n" +
            "}")
        .withTransformers("response-template")));

Each request will generate different random values, for example:

{
  "firstName": "John",
  "lastName": "Smith",
  "email": "john.smith@example.com"
}

Practical examples

Creating a realistic user profile

{
  "request": {
    "method": "GET",
    "urlPathPattern": "/api/users/[0-9]+"
  },
  "response": {
    "status": 200,
    "jsonBody": {
      "id": "{{request.pathSegments.[2]}}",
      "firstName": "{{random 'Name.first_name'}}",
      "lastName": "{{random 'Name.last_name'}}",
      "email": "{{random 'Internet.email_address'}}",
      "phone": "{{random 'PhoneNumber.phone_number'}}",
      "address": {
        "street": "{{random 'Address.street_address'}}",
        "city": "{{random 'Address.city'}}",
        "state": "{{random 'Address.state'}}",
        "zipCode": "{{random 'Address.zip_code'}}"
      },
      "company": "{{random 'Company.name'}}",
      "jobTitle": "{{random 'Job.title'}}"
    },
    "transformers": ["response-template"]
  }
}

Generating product data

{
  "request": {
    "method": "GET",
    "url": "/api/products"
  },
  "response": {
    "status": 200,
    "jsonBody": [
      {
        "id": 1,
        "name": "{{random 'Commerce.product_name'}}",
        "price": "{{random 'Commerce.price'}}",
        "category": "{{random 'Commerce.department'}}",
        "color": "{{random 'Color.name'}}",
        "material": "{{random 'Commerce.material'}}"
      }
    ],
    "transformers": ["response-template"]
  }
}

Available fake data types

The Faker extension supports a wide variety of data types across multiple categories. Here are some commonly used ones:

Personal Information

• Name.first_name - First name
• Name.last_name - Last name
• Name.full_name - Full name
• Name.name_with_middle - Name with middle name
• Name.prefix - Name prefix (Mr., Mrs., etc.)
• Name.suffix - Name suffix (Jr., Sr., etc.)

Contact Information

• Internet.email_address - Email address
• Internet.safe_email_address - Safe email address
• PhoneNumber.phone_number - Phone number
• PhoneNumber.cell_phone - Cell phone number

Address Information

• Address.street_address - Street address
• Address.city - City name
• Address.state - State name
• Address.state_abbr - State abbreviation
• Address.zip_code - ZIP code
• Address.country - Country name

Business & Work

• Company.name - Company name
• Company.industry - Industry
• Job.title - Job title
• Job.field - Job field
• Commerce.department - Department name
• Commerce.product_name - Product name
• Commerce.price - Price

Internet & Technology

• Internet.url - URL
• Internet.domain_name - Domain name
• Internet.ip_v4_address - IPv4 address
• Internet.ip_v6_address - IPv6 address
• Internet.mac_address - MAC address
• Internet.uuid - UUID

Dates & Times

• DateAndTime.birthday - Birthday
• DateAndTime.future - Future date

Text & Content

• Lorem.characters - Random characters
• Lorem.word - Random word
• Lorem.sentence - Random sentence
• Lorem.paragraph - Random paragraph

Food & Beverage

• Food.ingredient - Food ingredient
• Food.spice - Spice name
• Beer.name - Beer name
• Coffee.blend_name - Coffee blend

Entertainment

• Book.title - Book title
• Book.author - Book author
• Music.genre - Music genre
• Movie.title - Movie title

Finance

• Finance.credit_card - Credit card number
• Finance.iban - IBAN
• Finance.bic - BIC/SWIFT code

Regional Data

• Address.postcode_by_state.AL - Postcode for Alabama
• (Similar patterns for other US states)

For a complete reference of all available data types, see the Faker Extension Reference Documentation.

Locale support

By default, the Faker extension generates data in the en-US locale. The generated data will follow American conventions for names, addresses, phone numbers, and other locale-specific formats.

Combining with other helpers

The random helper works seamlessly with other WireMock template helpers:

{{!-- Capitalize a random first name --}}
{{capitalize (random 'Name.first_name')}}

{{!-- Create an email from random name parts --}}
{{toLowerCase (random 'Name.first_name')}}.{{toLowerCase (random 'Name.last_name')}}@example.com

{{!-- Format output with random data --}}
Hello {{random 'Name.first_name'}}, your order #{{randomValue type='NUMERIC' length=8}} has shipped!

Best practices

1. Use with response templating: Always enable response templating when using the Faker extension by adding "transformers": ["response-template"] to your stub.

2. Combine with request data: Mix random data with request parameters for more realistic responses:

   {
     "userId": "{{request.pathSegments.[2]}}",
     "userName": "{{random 'Name.full_name'}}",
     "timestamp": "{{now}}"
   }

3. Choose appropriate types: Select faker types that match your domain. For example, use Job.title for employee data rather than generic Lorem.word.

4. Test data consistency: Remember that the faker generates new random values on each request. If you need consistent data across requests, consider using stateful behaviour or storing values in scenarios.

See also

• Response Templating - Learn about all available template helpers
• Extending WireMock - Create your own custom extensions
• Adding Template Helpers - Build custom Handlebars helpers
• Data Faker Documentation - Full documentation for the underlying library