What is the best way to unit test a simple JsonResult?

Question

In the event of a successful AJAX call I want to return a simple object with Success = true

public ActionResult Foo(int id)
{
    // ...
    return Json(new {Success=true});
}

This works fine and the object my javascript receives looks like

{ Success : true }

but because the object returned is an anonymous type, I can't do (something like) the following in my test:

var result = (JsonResult)controller.AddNote(id, message);
dynamic data = result.Data;

// Assert
Assert.That(data.Success, Is.EqualTo(true));

So I tried returning an ExpandoObject which allows the test to work in the way I want but the the JSON sent back in the AJAX response is a mess, as detailed in this question.

[{"Key":"Success","Value":true}]

Is there a simple, clean way to achieve what seems like it should be easy, or is the only way to implement some custom serialization as in the linked question?

The result.Data you get in your unit test can not contain the json data because the jsonResult serializer is only run in the ExecuteResult method which is not run in a unit test. The "data" in your result.Data is just the anonymous data you assigned in your AddNote/Foo action. What you test is not json data! — Elisabeth, Sep 09 '12 at 18:28

score 1 · Accepted Answer · answered Nov 10 '11 at 19:04

Get the value with dynamic can work if you mark your controller assembly with the [assembly: InternalsVisibleTo("TestsProject")]. Because the classes generated for anonymous types are internal and runtime binding does not work with internal types. In this article you can find more information about this.

If you don't like this approach you can fallback to plain old reflection (hidden behind some helper methods):

[TestMethod]
public void AddNote1()
{
    ...
    var result = ((JsonResult)controller.AddNote(id, message));
    var data = result.Data;

    // Assert
    Assert.AreEqual(Get<bool>(data, "Success"), true);
 }

 private T Get<T>(object instance, string propertyName)
 {
     return (T) instance.GetType().GetProperty(propertyName).GetValue(instance, null);
 }

Use named classes instead of anonymous ones.
You have to use some kind of serialization workaround as you mentioned.

`InternalsVisibleTo` Legendary! – Greg B Nov 10 '11 at 22:08 — Greg B, Nov 10 '11 at 22:08

score 0 · Answer 2 · answered Nov 10 '11 at 18:30

What you can do is:

var js = new JavaScriptSerializer();
var response = new { id = 0, Status = false };
dynamic object = js.Deserialize(new StringReader(JSONText), response.GetType());

Assert.IsTrue(object.Success)

What this does is:

Create a JavaScriptSerializer.
Create a new anonymous object with the same layout as your json, so the serialiser knows what your object looks like
Deserialize the json into a new dynamic object.

The disadvantage of this is that you will not have IntelliSense on your json object, so any spelling mistake will not be caught by the compiler.

Note: I wrote the code here in stackoverflow, so there might be minor bugs in it. I did not test it, but it should work :P

Where would you get `JSONText` from? In the unit test, you don't have the actual HTTP body that goes over the wire... — Greg B, Nov 10 '11 at 18:52

What is the best way to unit test a simple JsonResult?

2 Answers2