Sample7_MockClient.md

Mock a client for testing using the Moq library

This sample illustrates how to use Moq to create a unit test that mocks the response from a ConfigurationClient method. For more examples of mocking, see the Azure.Data.AppConfiguration.Tests project.

Define method that uses ConfigurationClient

To show the usage of mocks, define a method that will be tested with mocked objects. For more details about this sample method, see "Update a Configuration If Unchanged" sample.

private static async Task<int> UpdateAvailableVmsAsync(ConfigurationClient client, int releasedVMs, CancellationToken cancellationToken)
{
    while (!cancellationToken.IsCancellationRequested)
    {
        ConfigurationSetting setting = await client.GetConfigurationSettingAsync("available_vms", cancellationToken: cancellationToken);
        var availableVmsCount = int.Parse(setting.Value);
        setting.Value = (availableVmsCount + releasedVMs).ToString();

        try
        {
            ConfigurationSetting updatedSetting = await client.SetConfigurationSettingAsync(setting, onlyIfUnchanged: true, cancellationToken);
            return int.Parse(updatedSetting.Value);
        }
        catch (RequestFailedException e) when (e.Status == 412)
        {
        }
    }

    cancellationToken.ThrowIfCancellationRequested();
    return 0;
}

Create and setup mocks

For this test, create a mock for the ConfigurationClient and Response.

var mockResponse = new Mock<Response>();
var mockClient = new Mock<ConfigurationClient>();

Then, set up the client methods that will be executed when GetConfigurationSettingAsync and SetConfigurationSettingAsync are called on the mock client.

Response<ConfigurationSetting> response = Response.FromValue(ConfigurationModelFactory.ConfigurationSetting("available_vms", "10"), mockResponse.Object);
mockClient.Setup(c => c.GetConfigurationSettingAsync("available_vms", It.IsAny<string>(), It.IsAny<CancellationToken>()))
    .Returns(Task.FromResult(response));
mockClient.Setup(c => c.SetConfigurationSettingAsync(It.IsAny<ConfigurationSetting>(), true, It.IsAny<CancellationToken>()))
    .Returns((ConfigurationSetting cs, bool onlyIfUnchanged, CancellationToken ct) => Task.FromResult(Response.FromValue(cs, new Mock<Response>().Object)));

Use mocks

Now to validate ReleaseVmsAsync without making a network call use ConfigurationClient mock.

ConfigurationClient client = mockClient.Object;
int availableVms = await UpdateAvailableVmsAsync(client, 2, default);
Assert.AreEqual(12, availableVms);