Just mock it as well as any other dependency:
var mock = new Mock<ILogger<BlogController>>();
ILogger<BlogController> logger = mock.Object;
var controller = new BlogController(logger);
or use this short equivalent:
logger = Mock.Of<ILogger<BlogController>>()
You probably will need to install Microsoft.Extensions.Logging.Abstractions
package to use ILogger<T>
.
Moreover, you can create a real logger:
var serviceProvider = new ServiceCollection()
.AddLogging()
.BuildServiceProvider();
var factory = serviceProvider.GetService<ILoggerFactory>();
var logger = factory.CreateLogger<BlogController>();