Asp.net-mvc – How to unit test Asp.net MVC fileUpload

asp.net-mvcfile uploadtddunit testing

Hello I am new in TDD development.
I came across this post for Using asp.net mvc to upload file
Phil Haack states that a class could be used for file upload control, in which he use the default HttpFileCollectionValueProvider:

[HttpPost]
public ActionResult Index(HttpPostedFileBase file) {

  if (file.ContentLength > 0) {
    var fileName = Path.GetFileName(file.FileName);
    var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileName);
    file.SaveAs(path);
  }

  return RedirectToAction("Index");
}

the value is bounded in a form as

<form action="" method="post" enctype="multipart/form-data">
  <label for="file">Filename:</label>
  <input type="file" name="file" id="file" />
  <input type="submit" />
</form>

Note that the HttpPostedFileBase is parsed as a parameter into the controller with the name "file" in the html form and as parsing parameter in Index controller.

I have two questions:
1. How can I verify the file.SaveAs method?
2. I am not quite sure how to unit test with this. In the test controller file I should have a fake HttpPostedFileBase but it is sealed. Does anyone have some strategies to deal with this?

Thank you very much!

Best Answer

My apologies if this isn't what you are asking but I would simply mock the HttpPostedFileBase in your test:

var file = MockRepository.GenerateStub<HttpPostedFileBase>();

and then set any expectations:

file.Expect(f => f.ContentLength).Return(1);
file.Expect(f => f.FileName).Return("myFileName");

then pass this to your controller method:

controller.Index(file);

So that you can mock the behaviour of your file. I'm not sure about the .SaveAs - have you overridden this method?

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The simplest way to deal with testing complex, multithreaded application code is this: If it's too complex to test, you're doing it wrong. If you have a single instance that has multiple threads acting upon it, and you can't test situations where these threads step all over each other, then your design needs to be redone. It's both as simple and as complex as this.

There are many ways to program for multithreading that avoids threads running through instances at the same time. The simplest is to make all your objects immutable. Of course, that's not usually possible. So you have to identify those places in your design where threads interact with the same instance and reduce the number of those places. By doing this, you isolate a few classes where multithreading actually occurs, reducing the overall complexity of testing your system.

But you have to realize that even by doing this, you still can't test every situation where two threads step on each other. To do that, you'd have to run two threads concurrently in the same test, then control exactly what lines they are executing at any given moment. The best you can do is simulate this situation. But this might require you to code specifically for testing, and that's at best a half step towards a true solution.

Probably the best way to test code for threading issues is through static analysis of the code. If your threaded code doesn't follow a finite set of thread safe patterns, then you might have a problem. I believe Code Analysis in VS does contain some knowledge of threading, but probably not much.

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Update:

Some 10 years later perhaps the best way to test a private method, or any inaccessible member, is via @Jailbreak from the Manifold framework.
@Jailbreak Foo foo = new Foo();
// Direct, *type-safe* access to *all* foo's members
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This way your code remains type-safe and readable. No design compromises, no overexposing methods and fields for the sake of tests.

If you have somewhat of a legacy Java application, and you're not allowed to change the visibility of your methods, the best way to test private methods is to use reflection.

Internally we're using helpers to get/set private and private static variables as well as invoke private and private static methods. The following patterns will let you do pretty much anything related to the private methods and fields. Of course, you can't change private static final variables through reflection.

Method method = TargetClass.getDeclaredMethod(methodName, argClasses);
method.setAccessible(true);
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And for fields:

Field field = TargetClass.getDeclaredField(fieldName);
field.setAccessible(true);
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1. TargetClass.getDeclaredMethod(methodName, argClasses) lets you look into private methods. The same thing applies for getDeclaredField.
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Best Answer

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