Custom Mock

Apidog provides powerful mock customization features that give you fine-grained control over API responses. This document introduces two approaches to customize mock data:

Field-Level Customization: Control specific fields while using smart mock for others

Full Response Customization: Define complete mock responses with expectations (fixed, conditional, or dynamic)

Field-Level Customization

Sometimes you need to define specific values for certain fields while letting Apidog automatically generate the rest. Apidog offers flexible methods for field-level control.

Setting Custom Field Values

1. Fixed Values

Specify a static value in the endpoint spec's mock field. Apidog will always return this exact value for that field, while using smart mock for unspecified fields.

Example:

2. Dynamic Values with Faker.js

Generate realistic random data using Apidog's dynamic values (based on Faker.js). Use the syntax:

{{$category.method}}

Common Examples:

Expression	Example Result
`{{$person.fullName}}`	Rachel Wheeler
`{{$internet.email}}`	Arno.Huels33@yahoo.com
`{{$commerce.productName}}`	Elegant Plastic Bike

Select dynamic values directly from the dropdown menu:

3. Parameterized Faker Methods

Pass parameters to dynamic value methods for specialized data generation using Apidog's enhanced Faker.js syntax.

Examples:

Use Case	Expression	Description
Integer range	`{{$number.int(min=0,max=10000)}}`	Random integer between 0 and 10,000
Readable phone	`{{$phone.number(style='human')}}`	Human-readable phone format
Multiple of N	`{{$number.int(multipleOf=3)}}`	Integer divisible by 3
Array element	`{{$helpers.arrayElement(['red','blue','green'])}}`	Random color from array
Date range	`{{$date.between(from='2024-01-01',to='2024-12-31',format='yyyy-MM-dd')}}`	Date between specified range

Explore the complete list of modules, methods, and parameters in the Dynamic Values Modules documentation.

4. Concatenating Multiple Expressions

Combine static text and multiple dynamic expressions to generate complex field values.

Example: Full Address Generation

{{$location.streetAddress}}, {{$location.city}}, {{$location.state}}, {{$location.zipCode}}, {{$location.country}}

Sample Output:

8507 Hudson Alley, Rochester, Wisconsin, 96512, United States

Each component is dynamically generated, creating unique, realistic addresses for every mock API call.

Mock Locales

Apidog supports customizable mock locales, allowing you to generate dynamic test data in different languages and formats that match your target region or audience. To learn more about configuring mock locales, visit Mock language (Locales).

Full Response Customization (Mock Expectations)

For complete control over mock responses, use mock expectations. This feature allows you to define fixed, conditional, or dynamic responses.

Creating Mock Expectations

Fixed Responses

Return the same data for every request by creating an unconditional expectation.

Steps:

Click New expectation

Add an expectation name and leave conditions blank

Fill in the response data you want to return, then save

Copy and use the provided mock URL to access this endpoint

Conditional Responses

Return different mock data based on request parameters. The mock engine evaluates conditions from top to bottom, returning the first matching expectation.

Supported Condition Types:

Parameter Type	Description
Query parameters	URL query strings
Path parameters	Dynamic URL segments
Header parameters	HTTP headers
Cookie parameters	Cookie values
Body parameters	JSON body fields (via JSON path)

Condition Behavior

Multiple conditions are combined with AND logic (all must match)

If no conditions match, Apidog falls back to the Mock method priority in Project Settings → Feature Settings → Mock Settings

Limitations

Body parameters support JSON only, not XML

Parameter conditions cannot use {{variables}}

Request body format must match the API spec (e.g., form-data, JSON)

IP address conditions can restrict responses to specific IPs

Dynamic Mock Data

Mock expectations support dynamic, randomized data using Faker.js and Nunjucks template syntax.

Example:

{
    "data": [
        {% for i in range(0, 20) %}
        {% if i>1 %},{% endif %}
        {
            "id": {{i}},
            "firstname": "{{$person.firstName}}",
            "lastname": "{{$person.lastName}}"
        }
        {% endfor %}
    ],
    "success": true
}

This generates:

Array of 20 user objects (id from 0 to 19)

Each with randomly generated first and last names

A constant "success": true field

Syntax Notes:

Syntax	Purpose
`{{$...}}`	Invokes Faker.js for random values
`{% for ... %}`	Nunjucks loop structure
`{{i}}`	Nunjucks loop variable (not an Apidog variable)

Important Differences

Apidog uses {{$person.firstName}} instead of native Faker.js faker.person.firstName()

Apidog project/environment variables ({{variable}}) are not available in mock expectations

Consult Faker.js and Nunjucks documentation for full syntax

Advanced Features

Custom Response Headers

Add custom headers to mock expectations to simulate authentication, pagination, or other API behaviors.

Advanced Response Properties

Configure additional response properties in the More tab:

Property	Purpose	Default
HTTP Status Code	Simulate errors or special cases	200
Response Delay	Simulate network latency (milliseconds)	0

Enable/Disable Expectations

Toggle expectations on or off independently for local and cloud mock environments from the expectation list.

Summary

Apidog's custom mock features provide:

Flexible field customization with fixed or dynamic values

Full response control through mock expectations

Conditional logic for parameter-based responses

Dynamic data generation using Faker.js and Nunjucks

Advanced simulation with custom headers, delays, and status codes

These features enable you to create robust, high-fidelity API simulations that accurately mirror production behavior!

Field-Level Customization#

Setting Custom Field Values#

1. Fixed Values#

2. Dynamic Values with Faker.js#

3. Parameterized Faker Methods#

4. Concatenating Multiple Expressions#

Full Response Customization (Mock Expectations)#

Creating Mock Expectations#

Fixed Responses#

Conditional Responses#

Dynamic Mock Data#

Advanced Features#

Custom Response Headers#

Advanced Response Properties#

Enable/Disable Expectations#

Summary#

Field-Level Customization

Setting Custom Field Values

1. Fixed Values

2. Dynamic Values with Faker.js

3. Parameterized Faker Methods

4. Concatenating Multiple Expressions

Full Response Customization (Mock Expectations)

Creating Mock Expectations

Fixed Responses

Conditional Responses

Dynamic Mock Data

Advanced Features

Custom Response Headers

Advanced Response Properties

Enable/Disable Expectations

Summary