Add support for non-JSON image mocks

[etpinard]

PR #850 made us realised that not all plotly.js features are JSON serializable e.g. Float32Array.

Possible solution: we could try to make the image tests routine and the test dashboard accept js files as mock. These js files would generate { data: [], layout: {} } object.

For example,

// in test/image/mocks/float32array.js

module.exports = function() {
  return {
    data: [{
      xy: new Float32Array([1,2,3,4])
    }]
  }
}

[etpinard]

Ping @plotly/plotly_js

Might be a good time to tackle this.

[etpinard]

So, I propose:

• keep the test/image/mocks/ folder intact. A lot of things (e.g. https://rreusser.github.io/plotly-mock-viewer/) are looking into this folder from http://raw.githubusercontent.com/ to do stuff with the JSON mocks.
• add a test/image/mock-generators/ folder with js files such that: test/image/mock-generators/some-mock.js would correspond to test/image/mocks/some-mock.json

then

• before npm run test-image, npm run baseline and npm run test-export we would run these test/image/mock-generators/ scripts in Node.js to then update text/image/mocks/ before generating baselines or running the image tests.

Now, we would still need to keep the output of test/image/mock-generators/ pure JSON (e.g. no TypedArrays). Down the road (when / if we switch to orca to run our image tests), we could try to generate the mocks in the front-end by adding a new orca renderer.

We would also need to find a way to keep test/image/mock-generators/ and test/image/mocks/ in-sync. I can think of two solutions:

• PRs that add files to test/image/mock-generators/ do not add the corresponding files in test/image/mocks/. test/image/mocks/ would be added during version commits.

  • 👍 no extra step (that could be sometimes forgotten) for developers
  • 👎 new test/image/mocks/ JSON files are not available until next plotly.js version

• PRs that add files to test/image/mock-generators/, must add the corresponding files in test/image/mocks/

  • 👍 test/image/mocks/ JSON files are always available
  • 👎 we would have to add extra machinery (probably a syntax test) to make sure test/image/mock-generators/ and test/image/mocks/ are in-sync

Thoughts?

[archmoj]

I'd vote for the second solution noting that few jasmine tests are dependent on the mocks; and one may want to run them in parallel.