Proposal: Add support for attachments

[bryanbcook]

Proposal, add testcase.attachment:

{
  "suites": [
     {
        "cases": [
             {
                "name": "",
                "status": "",
                "meta_data": {
                },
                "attachments": [
                   {
                      "name": "optional",
                      "path": "required - file name that the user provided",
                   }
                ]
             }
        ]
     }
   ]
}

Note that not all frameworks have built in support for including attachments as part of the result.

• Cucumber (🟨):

  It's unclear if cucumber supports this natively. The cucumber-json-converter project is supposedly a parser to represent the schema for various cucumber json outputs, but it doesn't explictly reference embeddings which is referenced elsewhere, eg XRay.

  "steps": [
         {
           "embeddings": [
             {
                 "mime_type": "text/plain",
                 "data": "{data base64}"
             },
             {
                 "mime_type": "text/plain",
                 "data": "{data base64}"
             }
         ...

  Note that the data appears to be embedded as base64. This makes the data easily transportable, but could lead towards larger files and a huger memory footprint for processing.

  The cucumber/common project refers to cucumber/messages which appears to be a successor to the JSON output format. We should consider adding a separate proposal to support cucumber message output.

• JUnit (🟨):

  The JUnit schema does not have defined attributes for attachments. There are implementations out there that read the test output for a specific string [[ATTACHMENT]/path/to/file]]

• MSTest (✅):

  Supported through TestContext.AddResultFile (link).

  According to the xsd (c:\program files\Microsoft Visual Studio\<version>\Xml\Schemas\vstst.xd), the files should appear under /TestRun/TestResults/*/ResultFiles

• NUnit (✅):

  Supported through TestContext.AddTestAttachment (link).

  Appears in the xml as <attachments> (link) under <testsuite> or <testcase>.

• xUnit (🟥):

  No native support in xUnit to capture attachments per test.