test: added snapshot tests

[abdul99ahad]

Proposed Changes

This PR aims to add snapshot tests.

• before and after webpack plugin applies
• can't run without loader / rules if no plugin applies
• should have alias when plugin applies
• you can apply custom rules
  • can work with plugins
  • can work without plugins

Checklist

To ensure you provided everything we need to look at your PR:

• Brief textual description of the changes present
• Visual demo attached
• Steps to try out present, i.e. using the @bpmn-io/sr tool
• Related issue linked via Closes {LINK_TO_ISSUE} or Related to {LINK_TO_ISSUE}

[nikku]

Not sure if we have different expectations on "snapshot tests", let me share mine:

• A snapshot test is when we, at one point in time, generate a snapshot "the expected shape" of a result
• As we progress in time, we validate new generations of the thing against the snapshot, to ensure that new generations comply with old expectations.

What you seem to do here, if I understand correctly, is to compare different "runs" for equality. Also a testing strategy, but I'm not sure what that one should accomplish. :)

[abdul99ahad]

What is the "expected shape" here. A custom plugin with webpack plugin config support?

[nikku]

Expected shape is "result of a webpack run with the plug-in enabled".

[nikku]

Regarding "what is snapshot testing", this may help. Let's discuss tomorrow.

[abdul99ahad]

Snapshot tests are a very useful tool whenever you want to make sure your UI does not change unexpectedly. (ref. https://jestjs.io/docs/snapshot-testing)

Looking at the PR #8, I now understand what we wanted to accomplish. There are two parts:

1. usage of webpack plugin when applied to plugins and when not applied (PR test: added snapshot tests #7)
2. plugins that uses webpack-plugin for bundling (PR Housekeeping + improve tests #8)

What you seem to do here, if I understand correctly, is to compare different "runs" for equality. Also a testing strategy, but I'm not sure what that one should accomplish. :)

This accomplishes runs of plugins that bundled using webpack plugin and without webpack plugin.