While Smart Mock automatically generates data based on your API specification, sometimes you need more control. Mock Expectations allow you to define custom mock responses with specific conditions, giving you full control over what the mock server returns.In this article, we'll learn how to create mock expectations for the Pet Store API, including fixed responses, conditional responses, and dynamic responses.
1. What Are Mock Expectations?#
Mock Expectations are custom mock responses that you define for specific scenarios. Unlike Smart Mock (which generates data automatically), mock expectations let you:Return fixed data that never changes
Return different responses based on request parameters
Return dynamic data using templates and expressions
2. When to Use Mock Expectations#
Use mock expectations when you need:Specific test scenarios: Test how your application handles specific responses (success, errors, edge cases)
Conditional responses: Return different data based on request parameters (e.g., different responses for different IDs)
Fixed responses: Always return the same data for consistency
Error simulation: Simulate error responses (404, 500, etc.) for testing
3. Creating a Fixed Mock Expectation#
Let's start with the simplest case: creating a mock expectation that always returns the same data.Example: Always Return a Specific Pet#
Suppose you want the GET /pets/{id} endpoint to always return a specific pet when called:Step 1: Open the Mock Tab#
1.
Open the GET /pets/{id} endpoint in your Pet Store API
Step 2: Create a New Expectation#
2.
Enter a name for the expectation (e.g., "Fixed Pet Response")
3.
Leave the Conditions section empty (no conditions = always matches)
4.
In the Response section, enter the JSON data you want to return:
{
"id": "pet_123",
"name": "Luna",
"species": "DOG",
"breed": "Golden Retriever",
"ageMonths": 24,
"status": "AVAILABLE",
"adoptionFee": 150.00
}
Step 3: Use the Mock URL#
1.
Copy the mock URL provided for this expectation
2.
Use it in your browser or application
3.
The mock server will always return the exact data you specified
4. Creating Conditional Mock Expectations#
The real power of mock expectations is conditional responsesβreturning different data based on request parameters.Example: Different Responses for Different Pet IDs#
Let's create expectations that return different pets based on the id path parameter:Step 1: Create Expectation for ID "pet_123"#
2.
Enter name: "Pet 123 - Luna"
3.
In Conditions, add a condition:Parameter Type: Path Parameter
{
"id": "pet_123",
"name": "Luna",
"species": "DOG",
"breed": "Golden Retriever",
"status": "AVAILABLE"
}
Step 2: Create Expectation for ID "pet_456"#
1.
Click "New expectation" again
2.
Enter name: "Pet 456 - Max"
3.
Parameter Type: Path Parameter
{
"id": "pet_456",
"name": "Max",
"species": "CAT",
"breed": "Persian",
"status": "PENDING"
}
Step 3: Test the Conditional Responses#
1.
Use the mock URL with id=pet_123 β Returns Luna's data
2.
Use the mock URL with id=pet_456 β Returns Max's data
3.
Use the mock URL with any other ID β Falls back to Smart Mock (if no conditions match)
How Matching Works#
Mock expectations are checked from top to bottom
The first matching expectation is used
If no conditions match, Apidog falls back to Smart Mock or response examples
5. Supported Condition Types#
You can create conditions based on:Query parameters: ?status=AVAILABLE
Path parameters: /pets/{id} where id=pet_123
Header parameters: Custom headers like X-User-Id
Cookie parameters: Cookie values
Body parameters: JSON body fields (JSON only)
Condition: Query parameter status equals "AVAILABLE"
Response: Returns only available pets
6. Creating Dynamic Mock Expectations#
You can also create expectations that generate dynamic data using Faker.js and Nunjucks templates.Example: Generate a List of Pets#
Let's create an expectation that generates a dynamic list of pets:2.
Enter name: "Dynamic Pet List"
3.
Leave conditions empty (or add your conditions)
4.
In Response, use a template:
{
"pets": [
{% for i in range(0, 5) %}
{% if i>0 %},{% endif %}
{
"id": "pet_{{i}}",
"name": "{{$person.firstName}}",
"species": "{{$helpers.arrayElement(['DOG','CAT'])}}",
"ageMonths": {{$number.int(min=1,max=120)}}
}
{% endfor %}
],
"total": 5
}
An array of 5 pet objects
Each with a unique ID (pet_0, pet_1, etc.)
Random names, species, and ages
Template Syntax#
{{$...}} β Faker.js expressions for random data
{% for ... %} β Nunjucks loops
{% if ... %} β Nunjucks conditionals
7. Advanced Features#
Mock expectations support additional features:Add custom headers to simulate authentication, pagination, etc.:1.
In the expectation, go to the Headers section
2.
Add headers like X-Total-Count: 100 or Authorization: Bearer token123
HTTP Status Codes#
Simulate different HTTP status codes:1.
In the expectation, click "More"
2.
Set HTTP Status Code to 404, 500, etc. (default is 200)
Response Delay#
Simulate slow API responses:2.
Set Response Delay (in milliseconds)
3.
Useful for testing how your application handles slow responses
Enable/Disable Expectations#
You can toggle expectations on/off for different environments (Local mock, Cloud mock) without deleting them.
8. Key Takeaways#
Mock Expectations give you full control over mock responses
Fixed expectations always return the same data
Conditional expectations return different data based on request parameters
Dynamic expectations use templates to generate variable data
Highest priority: Mock expectations override Smart Mock
Multiple conditions: You can combine query, path, header, and body parameters
Advanced features: Custom headers, status codes, and delays for realistic testing
Mock Expectations provide the flexibility to create sophisticated mock scenarios for testing and development. In the next article, we'll learn about Cloud Mockβhow to deploy mock servers in the cloud for team-wide access. Modified atΒ 2025-12-25 09:44:49
