public void Test()
{
Mock<IPostRepository> postRepositoryMock = new Mock<IPostRepository>();
PostController controller = new PostController(postRepositoryMock.Object);
postRepositoryMock.Setup(it => it.Get(It.IsAny<int?>()).Returns(new Post() { //here what you need to build your post object });
var result = controller.GetPost(1);
Assert.True(result != null,"Unexpected null result");
var retrievedPostResult = result as OkNegotiatedContentResult<Post>;
Assert.True(retrievedPostResult != null, "Unexpected null retrievedPost");
var retrievedPost = result.Content;
Assert.True(retrievedPost.Id == 1, "retrievedPost.Id is unexpected")
}
}
}