How to mock an IFormFile for a unit/integration test in ASP.NET Core 1 MVC 6?

Question

I want to write tests for uploading of files in ASP.NET Core 1 but can\'t seem to find a nice way to mock/instanciate an object derived from IFormFile. Any suggestions on ho

Answer 1

Adding on harishr's answer with a set lenght (which was what I needed for my Blob.Upload() to work).

private IFormFile CreateTestFormFile(string p_Name, string p_Content)
{
    byte[] s_Bytes = Encoding.UTF8.GetBytes(p_Content);

    return new FormFile(
        baseStream: new MemoryStream(s_Bytes),
        baseStreamOffset: 0,
        length: s_Bytes.Length,
        name: "Data",
        fileName: p_Name
    );
}

Answer 2

Easier would be to create an actual in-memory instance

 IFormFile file = new FormFile(new MemoryStream(Encoding.UTF8.GetBytes("This is a dummy file")), 0, 0, "Data", "dummy.txt");

Answer 3

Assuming you have a Controller like..

public class MyController : Controller {
    public Task<IActionResult> UploadSingle(IFormFile file) {...}
}

...where the IFormFile.OpenReadStream() is accessed with the method under test. You can create a test using Moq mocking framework to simulate the stream data.

[TestClass]
public class IFormFileUnitTests {
    [TestMethod]
    public async Task Should_Upload_Single_File() {
        //Arrange
        var fileMock = new Mock<IFormFile>();
        //Setup mock file using a memory stream
        var content = "Hello World from a Fake File";
        var fileName = "test.pdf";
        var ms = new MemoryStream();
        var writer = new StreamWriter(ms);
        writer.Write(content);
        writer.Flush();
        ms.Position = 0;
        fileMock.Setup(_ => _.OpenReadStream()).Returns(ms);
        fileMock.Setup(_ => _.FileName).Returns(fileName);
        fileMock.Setup(_ => _.Length).Returns(ms.Length);

        var sut = new MyController();
        var file = fileMock.Object;

        //Act
        var result = await sut.UploadSingle(file);

        //Assert
        Assert.IsInstanceOfType(result, typeof(IActionResult));
    }
}