C# Integration Testing Controller with FromForm binding to IFormFile property

Question

I'm using:

Visual Studio 2017 Pro
dotnet core sdk 2.2.102
XUnit 2.4.1

What I'm trying to do

Integration test an API Controller Method that accepts Form Data.

Setup

API route in my controller that accepts a CommandObject using the [FromForm] attribute
One of the properties of the CommandObject is of type List<IFormFile>, this is designed to manage any files that are part of the request
The Controller method works as expected when I test it manually from Postman.

The Problem

The Files are not bound to the List<IFormFile> property. Everything else works as expected, but the files do not. The is the first time I've used Multipart Form Data, so am not sure what to try.

When I debug the test, you can see everything works except for the Documents property (Note, this doesn't match 100% with the code below, because I've had to obfuscate some stuff)

Stuff I've looked at

There is a lot of stuff relating to multipart form data, some of the solutions I've tried are:

MyIntegrationTest.cs

There's a lot of code behind the setup of my integration tests. If I post it all here I don't think it will be very helpful. The most important piece of information is that variable server is of type Microsoft.AspNetCore.TestHost.TestServer

[Fact]
async Task Post_ItemAsync_HappyPath_ReturnsOKStatusCode()
{
    var fileDir = @"C:/path/to/files";
    var fileNames = new string[] { "test.docx", "test.txt" };

    using (var server = CreateTestServer())
    {
        // Arrange
        var formData = new MultipartFormDataContent()
        {
            { new StringContent("Test Title"), "Title" },
            { new StringContent("Test Description"), "Description" },
            { new StringContent("String_1"), "AListOfStrings" },
            { new StringContent("String_2"), "AListOfStrings" },
            { new StringContent("3"), "NumberOfThings" }
        };

        foreach (var fileName in fileNames)
        {
            var document = File.ReadAllBytes($"{fileDir}/{fileName}");
            formData.Add(new ByteArrayContent(document), "file", fileName);
        }

        string formDataBoundary = String.Format("----------{0:N}", Guid.NewGuid());
        string contentType = "multipart/form-data; boundary=" + formDataBoundary;

        var request = new HttpRequestMessage(HttpMethod.Post, "api/v1/item")
        {
            Headers =
            {
                { HttpRequestHeader.ContentType.ToString(), contentType }
            },
            Content = formData
        };

        // Act
        var response = await server.CreateClient().SendAsync(request);

        // Assert
        Assert.Equal(HttpStatusCode.OK, response.StatusCode);

        // Cleanup
        ...
    }
}

MyController.cs

[HttpPost]
ProducesResponseType((int)HttpStatusCode.OK)]
[ProducesResponseType((int)HttpStatusCode.BadRequest)]
public async Task<IActionResult> CreateItemAsync([FromForm]CreateItemCommand command)
{
    bool commandResult = false;

    commandResult = await _mediator.Send(command);

    if (!commandResult)
    {
        return BadRequest();
    }

    return Ok();
}

CreateItemCommand.cs

[DataContract]
public class CreateItemCommand
    :IRequest<bool>
{
    [DataMember]
    public string Title { get; set; }

    [DataMember]
    public string Description { get; set; }

    [DataMember]
    public HashSet<string> AListOfThings { get; set; }

    [DataMember]
    public int NumberOfThings { get; set; }

    [DataMember]
    public List<IFormFile> Documents { get; private set; }

    public CreateITemCommand()
    {
        AListOfThings = new HashSet<string>();
    }

    public CreateItemCommand(string title, string description, HashSet<string> aListOfThings, int NumberOfThings, List<IFormFile> documents)
        : this()
    {
        Title = title;
        Description = description;
        AListOfStrings = aListOfStrings;
        NumberOfThings = numberOfThings;
        Documents = documents;
    }
}

Nkosi · Accepted Answer · 2019-06-23T10:11:18.980

The form data boundary should be added to the MultipartFormDataContent upon initialization and the name of the files need to match the model's desired property to be populated.

//...

// Arrange
string formDataBoundary = String.Format("----------{0:N}", Guid.NewGuid());

var formData = new MultipartFormDataContent(formDataBoundary) { //<---- NOTE HERE
    { new StringContent("Test Title"), "Title" },
    { new StringContent("Test Description"), "Description" },
    { new StringContent("String_1"), "AListOfStrings" },
    { new StringContent("String_2"), "AListOfStrings" },
    { new StringContent("3"), "NumberOfThings" }
};

foreach (var fileName in fileNames) {
    var document = File.ReadAllBytes($"{fileDir}/{fileName}");
    formData.Add(new ByteArrayContent(document), "Documents", fileName); //<-- NOTE HERE
}

// Act
var response = await server.CreateClient().PostAsync("api/v1/item", formData);

//...

The model's Documents property would need to be set as public so that the model binder can populate it when parsing the form data.

C# Integration Testing Controller with FromForm binding to IFormFile property

1 Answers1