WireMock: How to mock file download process?

Question

I'm new inWireMock. I am running the WireMock server as a standalone process. I am able to mock simple rest api, by configuring json files under /mappings folder. Now, I want to mock a file downloading end point. How can I do that?

I don't know if it helps, the end point is in Java/Spring, which looks like this:

@RequestMapping(value = "xxx/get", method = {RequestMethod.GET})
public ResponseEntity<Object> getFile(HttpServletResponse response) throws Exception {

    final Resource fileResource = fileResourceFactoryBean.getObject();

    if (fileResource.exists()) {
        try (InputStream inputStream = fileResource.getInputStream()) {
            IOUtils.copy(inputStream, response.getOutputStream());

            response.setContentType("application/octet-stream");
            response.setHeader("Content-Disposition", "attachment; filename=" + fileResource.getFilename());

            response.flushBuffer();
            inputStream.close();

            return new ResponseEntity<>(HttpStatus.OK);
        } catch (Exception e) {
            LOGGER.error("Error reading file: ", e);
            return new ResponseEntity<Object>("Error reading file.", HttpStatus.BAD_REQUEST);
        }
    }

    return new ResponseEntity<Object>(fileResource.getFilename() + " not found.", HttpStatus.BAD_REQUEST);
}

My response section in the mappings json file looks like this:

"response": {
    "status": 200,
    "bodyFileName": "fileName", // file under __files directory
    "headers": {
      "Content-Type": "application/octet-stream"
    }
  }

Segno

Answer 1

A very late answer, but the only working solution I found is this:

"response": {
            "status": 200,
            "headers": {
                "Content-Type": "image/jpeg"
            },
            "base64Body": "2wBDAAQDAwQDAwQE...=="       
        }

Where I put the image content, encoded in Base64, directly in the mapping file.

More or less ok...for small files.

In java, it seems a bit more handy :

.willReturn( aResponse()
     .withBody( myImage.getBytes() )

Using the json DSL, you only have:

• bodyFileName (NB: the doc says: "body files are expected to be in UTF-8 format")
• base64Body
• but something like base64BodyFileName is NOT possible :-(

Balladist

Answer 2

File downloads are really no different than sending markup or JSON. Web browsers treat a file as a download if they don't recognise the MIME type as one it can render.

To make this happen with WireMock, try:

• Setting the Content-Type header on the response to application/octet-stream
• Setting the response to use a body file (the one you wish to download)

Unsought

I have updated my question with the response content I am using. It matches what you're suggesting. But it's not working for me. Do you see anything wrong with that piece of response content? Could you please take a took? Thanks Tom. – Segno

Can you describe what you're trying to do in a bit more detail? How are you testing the stub? With a web browser, or programmatic client? What is the failure you're seeing? – Unsought

Actually, my client is a cordova android app that makes a server call to download a (database) file. I'm using WireMock to mock the web app. The error says: Matched response definition: (no response definition configured) – Segno

OK, that means it's the request part that isn't correct. I suggest checking the URL, method and request headers you've specified match what the app is sending. Update your original post with details if you can't see anything obviously wrong. – Unsought

WireMock is receiving the request per console message. The client is getting 404 error. The console log from WireMock says the following: Response: HTTP/1.1 404 (no headers) – Segno

So WireMock isn't matching the request. If you post the full details of your stub mapping and the request that's being made I might be able to help figure out why. – Unsought

You could also try the c# dotnet version : github.com/WireMock-Net/WireMock.Net – Eponymous

Answer 3

I use mapping like:

{
  "request": {
    "method": "GET",
    "url": "/files/b8b6461d-75c7-4908-a418-777140912059"
  },
  "response": {
    "status": 200,
    "bodyFileName": "file.pdf",
    "headers": {
      "Content-Type": "application/pdf",
      "Content-Disposition": "attachment;filename=\"file.pdf\""
    }
  }
}

file.pdf is actual file in __files directory. It works as expected for client using this stub.

Menstrual