In a test environment during test runtime, how can I assert values copied to the clipboard via the vscode.env.clipboard.writeText(value) method?

[jtroussard]

Summary

I'm testing a VSCode extension that uses vscode.env.clipboard.writeText(...) to copy a generated string to the system clipboard.

In my test, I want to assert that the clipboard contains the expected value. However, vscode.env.clipboard.readText() always returns an empty string during test runs, even when retrying with delays.

The clipboard write is confirmed to execute with valid content. No mocking or stubbing of the clipboard API is involved. This is using @vscode/test-electron with Mocha and running live extension code.

Goal

I need a way to perform a real clipboard assertion inside the test using VSCode’s API

Environment

macOS (M3)
VSCode 1.103.x
@vscode/test-electron 2.4.1
vscode 1.1.37
Node 18

More details:

https://stackoverflow.com/questions/79738104/vscode-extension-test-runner-how-to-assert-values-copied-to-the-clipboard

Repo and Branch

https://github.com/jtroussard/treematic/tree/output-check-tests

More context

https://stackoverflow.com/questions/79738104/vscode-extension-test-runner-how-to-assert-values-copied-to-the-clipboard

Any insights appreciated.

[alefragnani]

Hi @jtroussard ,

My Copy Word in Cursor extension plays with Clipboard API, and I do some tests as well, but instead of writing and reading from the clipboard, I do half in the clipboard and half in the VS Code Editor.

Besides some delay issues (as you commented) when I started to add tests, it was working just fine, up until some recent issues in CI, which I must address.

Feel free to take a look at my extension's source to see if something may help you.

    ...
        // put some text in the clipboard
        await vscode.env.clipboard.writeText('thank');

        // put the cursor at the `taking'
        const selDestiny = new vscode.Selection(new vscode.Position(2, 31), new vscode.Position(2, 31));
        vscode.window.activeTextEditor.selection = selDestiny;

        // runs the command
        await vscode.workspace.getConfiguration('copyWord').update('pasteWordBehavior', 'original');
        await vscode.commands.executeCommand('copy-word.paste');
        await vscode.workspace.getConfiguration('copyWord').update('pasteWordBehavior', 'replaceWordAtCursor');

        // get the word at the position of the paste
        const text = vscode.window.activeTextEditor.document.getText(
            vscode.window.activeTextEditor.document.getWordRangeAtPosition(vscode.window.activeTextEditor.selection.active));

        await vscode.commands.executeCommand('undo');

        // assert - the new select must be `tathankking`
        assert.ok(text === 'tathankking');

More details in the repo: https://github.com/alefragnani/vscode-copy-word/blob/master/src/test/suite/commands.test.ts

Hope this helps