How do I test a Azure AD protected Web API in with

I've created a multi tenant Web API that works just fine. Now I want to build a native client for testing. The Web API app is defined in one tenant. The test app is defined in another tenant that has given admin consent to the Web API.

I want to use the native app to authenticate with username and password in my (non-interactive) integration tests. I cannot use certificate/app-only authentication because I need a real user context.

Getting a token

var userCredential = new UserCredential("admin@clienttenant.onmicrosoft.com", "password");
var context = new AuthenticationContext("https://login.windows.net/common");

return context.AcquireToken("https://webapitenant.onmicrosoft.com/webApiResourceUri", testClientId, userCredential).AccessToken;

The problem with this code is that it doesn't work until I've given admin consent to the native app, even if the user is in the same tenant as the app registration.

Exception thrown:

'Microsoft.IdentityModel.Clients.ActiveDirectory.AdalServiceException' in Microsoft.IdentityModel.Clients.ActiveDirectory.dll

Additional information: 
AADSTS65001: The user or administrator has not consented to use the application with ID 'nativeclientid'. Send an interactive authorization request for this user and resource.

Since tests aren't interactive I have to create a console application that uses the above code but with PromptBehaviour.Always. This will prompt me for username and password and show a consent form. After I give consent the tests that is using the same native app registration starts working.

Is there a way to accept the consent form without a interactive GUI?

At the moment there is no other way to write user consent without some sort of user experience. (Which makes sense right?)

If you use the Azure Management Portal, as an administrator of your tenant, all the apps you create should automatically be consented for the resources you selected. This is because the Azure Management Portal specifically will write those consent links as you save your client application.

If you use other portals or APIs to create your application, then you will need to consent to the application at least one time. You do not need to necessarily put prompt behavior on your application to get the consent screen. You can just generate the URL for signing into your application, which will also take you through the consent experience:

https://login.microsoftonline.com/<TenantID>/oauth2/authorize?client_id=<AppID>&response_type=code&redirect_uri=<RedirectURI>&resource=<ResourceURI>&prompt=admin_consent

Note that we added a "prompt=admin_consent" at the end which will consent to the application on-behalf of the whole tenant. With this kind of consent, you will only need to do it once per application to get it working.

I hope this helps!