How to use user secrets in a dotnet core test project : <p>I want to store a database connection string for my integration tests as a user secret. My project.json looks like this:</p>

<pre><code>{
  ...

  "dependencies": {
    ...
    "Microsoft.Extensions.Configuration.UserSecrets": "1.1.0"        
  },

  "tools": {
    "Microsoft.Extensions.SecretManager.Tools": "1.1.0-preview4-final"
  },

  "userSecretsId": "dc5b4f9c-8b0e-4b99-9813-c86ce80c39e6"
}
</code></pre>

<p>I've added the following to the constructor of my test class:</p>

<pre><code>IConfigurationBuilder configurationBuilder = new ConfigurationBuilder()
    .AddJsonFile("appsettings.json")
    .AddUserSecrets();
</code></pre>

<p>However when I run the tests the following exception is thrown when it hits that line:</p>

<pre><code>An exception of type 'System.InvalidOperationException' occurred in Microsoft.Extensions.Configuration.UserSecrets.dll but was not handled in user code

Additional information: Could not find 'UserSecretsIdAttribute' on assembly 'dotnet-test-nunit, Version=3.4.0.0, Culture=neutral, PublicKeyToken=null'.
</code></pre>

<p>Have I missed something or is what I'm trying to do not supported?</p>
