Remove unnecessary step

docs/developers/contributing.md

@@ -52,13 +52,11 @@ You can create a new image-based test by following the steps below:
 - Create a JS file ([example](https://github.com/chartjs/Chart.js/blob/f7b671006a86201808402c3b6fe2054fe834fd4a/test/fixtures/controller.bubble/radius-scriptable.js)) or JSON file ([example](https://github.com/chartjs/Chart.js/blob/4b421a50bfa17f73ac7aa8db7d077e674dbc148d/test/fixtures/plugin.filler/fill-line-dataset.json)) that defines chart config and generation options.
 - Add this file in `test/fixtures/{spec.name}/{feature-name}.json`.
 - Add a [describe line](https://github.com//chartjs/Chart.js/blob/4b421a50bfa17f73ac7aa8db7d077e674dbc148d/test/specs/plugin.filler.tests.js#L10) to the beginning of `specs/{spec.name}.js` if it doesn't exist yet.
-- Set `"debug": true` in the JSON file to prevent the canvas destruction when running tests.
 - Run `gulp unittest --watch --inputs=test/specs/{spec.name}.js`.
 - Click the *"Debug"* button (top/right): a test should fail with the associated canvas visible.
 - Right click on the chart and *"Save image as..."* `test/fixtures/{spec.name}/{feature-name}.png`.
 - Refresh the browser page (`CTRL+R`): test should now pass
 - Verify test relevancy by changing the feature values *slightly* in the JSON file.
-- Remove `debug: true` from the JSON file.
 
 Tests should pass in both browsers. In general, we've hidden all text in image tests since it's quite difficult to get them passing between different browsers. As a result, it is recommended to hide all scales in image-based tests. It is also recommended to disable animations. If tests still do not pass, adjust [`tolerance` and/or `threshold`](https://github.com/chartjs/Chart.js/blob/1ca0ffb5d5b6c2072176fd36fa85a58c483aa434/test/jasmine.matchers.js) at the beginning of the JSON file keeping them **as low as possible**.