public async void GetDocuments_ShouldCallService()
{
// Arrange
_mockService.Setup(_ => _.GetDocuments(It.IsAny <string>()))
.ReturnsAsync(It.IsAny <List <CouncilTaxDocumentReference> >());
// Act
var result = await _controller.GetDocuments(It.IsAny <string>());
// Assert
_mockService.Verify(_ => _.GetDocuments(It.IsAny <string>()), Times.Once);
var actionResult = Assert.IsType <OkObjectResult>(result);
Assert.Equal(200, actionResult.StatusCode);
}