How to mock ActionExecutingContext with Moq? - asp.net-mvc

Question

I am trying to test the following filter:
using Microsoft.AspNet.Mvc;
using Microsoft.AspNet.Mvc.Filters;
namespace Hello
{
public class ValidationFilter : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
if (!filterContext.ModelState.IsValid) {
filterContext.Result = new BadRequestObjectResult(filterContext.ModelState);
}
}
}
}
I am trying to mock the ActionFilterAttribute using Moq.
I am using Mvc 6.0.0-rc1
My first try:
var context = new ActionExecutingContext(
new ActionContext(Mock.Of<HttpContext>(), new RouteData(), new ActionDescriptor()),
new IFilterMetadata[] { filter, },
new Dictionary<string, object>(),
controller: new object());
But I could not override the ModelState. It looks to be readonly: https://github.com/aspnet/Mvc/blob/6.0.0-rc1/src/Microsoft.AspNet.Mvc.Abstractions/ActionContext.cs#L25
Then I tried:
var contextMock = new Mock<ActionExecutingContext>(
new ActionContext(Mock.Of<HttpContext>(), new RouteData(), new ActionDescriptor()),
new IFilterMetadata[] { filter, },
new Dictionary<string, object>());
But when I call filter.OnActionExecuting(contextMock.Object) I get the following error:
Castle.DynamicProxy.InvalidProxyConstructorArgumentsException : Can not instantiate proxy of class: Microsoft.AspNet.Mvc.Filters.ActionExecutingContext.
Could not find a constructor that would match given arguments:
Microsoft.AspNet.Mvc.ActionContext
Microsoft.AspNet.Mvc.Filters.IFilterMetadata[]
System.Collections.Generic.Dictionary`2[System.String,System.Object]
How to test a filter that uses ModelState?

Answer 1

I just stumbled on the same problem and solved it in this way.
[Fact]
public void ValidateModelAttributes_SetsResultToBadRequest_IfModelIsInvalid()
{
var validationFilter = new ValidationFilter();
var modelState = new ModelStateDictionary();
modelState.AddModelError("name", "invalid");
var actionContext = new ActionContext(
Mock.Of<HttpContext>(),
Mock.Of<RouteData>(),
Mock.Of<ActionDescriptor>(),
modelState
);
var actionExecutingContext = new ActionExecutingContext(
actionContext,
new List<IFilterMetadata>(),
new Dictionary<string, object>(),
Mock.Of<Controller>()
);
validationFilter.OnActionExecuting(actionExecutingContext);
Assert.IsType<BadRequestObjectResult>(actionExecutingContext.Result);
}

Answer 2

If someone was wondering how to do this when you inherit from IAsyncActionFilter
[Fact]
public async Task MyTest()
{
var modelState = new ModelStateDictionary();
var httpContextMock = new DefaultHttpContext();
httpContextMock.Request.Query = new QueryCollection(new Dictionary<string, StringValues> {}); // if you are reading any properties from the query parameters
var actionContext = new ActionContext(
httpContextMock,
Mock.Of<RouteData>(),
Mock.Of<ActionDescriptor>(),
modelState
);
var actionExecutingContext = new ActionExecutingContext(
actionContext,
new List<IFilterMetadata>(),
new Dictionary<string, object>(),
Mock.Of<Controller>()
)
{
Result = new OkResult() // It will return ok unless during code execution you change this when by condition
};
Mymock1.SetupGet(x => x.SomeProperty).Returns("MySomething");
Mymock2.Setup(x => x.GetSomething(It.IsAny<string>(), It.IsAny<string>())).ReturnsAsync(true);
var context = new ActionExecutedContext(actionContext, new List<IFilterMetadata>(), Mock.Of<Controller>());
await _classUnderTest.OnActionExecutionAsync(actionExecutingContext, async () => { return context; });
actionExecutingContext.Result.Should().BeOfType<OkResult>();
}