This adds an `assertHeap` function that can be used in tests. It
takes a heap snapshot, and asserts the state of classes in memory. This
works in Node and the Electron sandbox, but is a no-op in the browser.
Snapshots are process asynchronously and will report failures at the end
of the suite.
This method should be used sparingly (e.g. once at the end of a suite to
ensure nothing leaked before), as gathering a heap snapshot is fairly
slow, at least until V8 11.5.130 (https://v8.dev/blog/speeding-up-v8-heap-snapshots).
When used, the function will ensure the test has a minimum timeout
duration of 20s to avoid immediate failures.
It takes options containing a mapping of class names, and assertion functions
to run on the number of retained instances of that class. For example:
```ts
assertSnapshot({
classes: {
ShouldNeverLeak: count => assert.strictEqual(count, 0),
SomeSingleton: count => assert(count <= 1),
}
});
```
Closes https://github.com/microsoft/vscode/issues/191920
* eng: add support for snapshot tests
This adds Jest-like support for snapshot testing.
Developers can do something like:
```js
await assertSnapshot(myComplexObject)
```
The first time this is run, the snapshot expectation file is written
to a `__snapshots__` directory beside the test file. Subsequent runs
will compare the object to the snapshot, and fail if it doesn't match.
You can see an example of this in the test for snapshots themselves!
After a successful run, any unused snapshots are cleaned up. On a failed
run, a gitignored `.actual` snapshot file is created beside the
snapshot for easy processing and inspection.
Shortly I will do some integration with the selfhost test extension to
allow developers to easily update snapshots from the vscode UI.
For #189680
cc @ulugbekna @hediet
* fix async stacktraces getting clobbered
* random fixes
* comment out leak detector, for now
* add option to snapshot file extension
* tests - run unit tests also against node.js
* fixes
* fail if major node.js version mismatch
* -tfs is unsupported
* Add `@ts-check` and remove `jsdom`
* tests - process.env layer breaker
* Improve loader config
* skip one test
* address todos
* try to force color output
* Use a file: URI as baseUrl
Co-authored-by: Alex Dima <alexdima@microsoft.com>
