title: .NET Core Unit Testing - Mock IOptions<T>
body: <p>I feel like I'm missing something really obvious here. I have classes that require injecting of options using the .NET Core <code>IOptions</code> pattern(?). When I unit test that class, I want to mock various versions of the options to validate the functionality of the class. Does anyone know how to correctly mock/instantiate/populate <code>IOptions&lt;T&gt;</code> outside of the Startup class?</p>
  <p>Here are some samples of the classes I'm working with:</p>
  <p>Settings/Options Model</p>
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Threading.Tasks;
  
  namespace OptionsSample.Models
  {
      public class SampleOptions
      {
          public string FirstSetting { get; set; }
          public int SecondSetting { get; set; }
      }
  }
  </code></pre>
  <p>Class to be tested which uses the Settings:</p>
  <pre><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Threading.Tasks;
  using OptionsSample.Models
  using System.Net.Http;
  using Microsoft.Extensions.Options;
  using System.IO;
  using Microsoft.AspNetCore.Http;
  using System.Xml.Linq;
  using Newtonsoft.Json;
  using System.Dynamic;
  using Microsoft.Extensions.Logging;
  
  namespace OptionsSample.Repositories
  {
      public class SampleRepo : ISampleRepo
      {
          private SampleOptions _options;
          private ILogger&lt;AzureStorageQueuePassthru&gt; _logger;
  
          public SampleRepo(IOptions&lt;SampleOptions&gt; options)
          {
              _options = options.Value;
          }
  
          public async Task Get()
          {
          }
      }
  }
  </code></pre>
  <p>Unit test in a different assembly from the other classes:</p>
  <pre><code>using OptionsSample.Repositories;
  using OptionsSample.Models;
  using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Threading.Tasks;
  using Xunit;
  using Microsoft.Extensions.Logging;
  using Microsoft.AspNetCore.Http;
  using Microsoft.Extensions.Options;
  using Microsoft.Extensions.DependencyInjection;
  using Microsoft.Extensions.Configuration;
  
  namespace OptionsSample.Repositories.Tests
  {
      public class SampleRepoTests
      {
          private IOptions&lt;SampleOptions&gt; _options;
          private SampleRepo _sampleRepo;
  
  
          public SampleRepoTests()
          {
              //Not sure how to populate IOptions&lt;SampleOptions&gt; here
              _options = options;
  
              _sampleRepo = new SampleRepo(_options);
          }
      }
  }
  </code></pre>