Introduction

When working with Azure’s App Configuration service in .NET, it’s common to use the Azure.Data.AppConfiguration.ConfigurationClient class to interact with our configuration settings. In a unit test scenario, however, interacting directly with the Azure service is not ideal. Instead, we can mock the ConfigurationClient using a library like Moq to simulate its behaviour, allowing us to test our code in isolation.

In this blog post, we’ll explore how to mock the ConfigurationClient and simulate the paging behaviour of its GetConfigurationSettings method using Moq. This allows us to unit test our code effectively without making actual calls to Azure.

Setup

Before diving into the code, ensure we have the following packages installed in our project:

• Azure.Data.AppConfiguration
• Moq
• Azure.Core

we can install them via NuGet:

dotnet add package Azure.Data.AppConfiguration
dotnet add package Moq
dotnet add package Azure.Core

Example Code

Let’s look at an example where we mock the GetConfigurationSettings method of ConfigurationClient. We’ll create a mock response that returns a list of ConfigurationSetting objects and simulate the paging behaviour.

// Arrange
var endpoint = "https://example.azure-appconfig.net";
var filter = "KeyFilter";
var label = string.Empty;
var expectedValues = new List<string> { "Value1", "Value2", "Value3" };

// Create a mock of the ConfigurationClient
var configurationClient = new Mock<ConfigurationClient>();

// Simulate a page of ConfigurationSetting objects
var configurationSettingPage = Page<ConfigurationSetting>.FromValues(
    new List<ConfigurationSetting>
 {
        new ConfigurationSetting("Key1", "Value1", label),
        new ConfigurationSetting("Key2", "Value2", label),
        new ConfigurationSetting("Key3", "Value3", label)
 },
    continuationToken: null,
    response: Mock.Of<Response>()
);

// Create a Pageable response that contains the page
var response = Pageable<ConfigurationSetting>.FromPages(
    new List<Page<ConfigurationSetting>> { configurationSettingPage }
);

// Set up the mock to return the simulated pageable response when GetConfigurationSettings is called
configurationClient
 .Setup(x => x.GetConfigurationSettings(It.IsAny<SettingSelector>(), It.IsAny<CancellationToken>()))
 .Returns(response);

Explanation

Let’s break down the code step by step:

1. Arrange the Test Setup: We start by defining the endpoint, filter, and label typically used in the GetConfigurationSettings method call. We also define the expected values we want our mock to return.
2. Create a Mock ConfigurationClient: We use Moq to create a mock instance of the ConfigurationClient.
3. Simulate a Page of Configuration Settings: The Page<ConfigurationSetting> class represents a single page of results. We use the FromValues method to create a page containing three ConfigurationSetting objects. Each setting has a key and value pair.
4. Create a Pageable Response: The Pageable<T> class represents a sequence of pages. We use FromPages to create a pageable response containing the page we just created. This simulates the response we’d get from the real ConfigurationClient.
5. Set up the Mock Behavior: Finally, we set up the mock ConfigurationClient to return our pageable response when the GetConfigurationSettings method is called with any SettingSelector and CancellationToken.

Conclusion

Mocking Azure services like ConfigurationClient allows us to isolate our unit tests from external dependencies, ensuring that our tests are fast, reliable, and repeatable. By using Moq and Azure SDK’s built-in paging support, we can simulate complex behaviours like pagination and ensure our code handles these scenarios correctly.

For more detailed information on mocking with the Azure SDK and Moq, refer to the official Microsoft documentation.