Testing

@adecore/lsp/testing holds a language server for tests and the memory transport, so a session runs in bun test without a process, a network or an installed server.

import { expect, test } from 'bun:test';
import { LspSession, pathToFileUri } from '@adecore/lsp';
import { createMemoryTransportPair, FakeLanguageServer } from '@adecore/lsp/testing';

test('the server follows the document', async () => {
    const [client, serverEnd] = createMemoryTransportPair();
    const server = new FakeLanguageServer(serverEnd, {
        capabilities: { textDocumentSync: 2, hoverProvider: true },
        handlers: { 'textDocument/hover': () => ({ contents: { kind: 'plaintext', value: 'A value' } }) }
    });
    const session = new LspSession(client, { rootUri: pathToFileUri('/work') });

    await session.initialize();
    const document = session.openDocument({ uri: pathToFileUri('/work/example.ts'), languageId: 'typescript', text: 'const value = 1;' });

    expect(await document.hover({ line: 0, character: 6 })).not.toBeNull();
    await document.updateText('const value = 2;');
    expect(server.documents.get(document.uri)?.text).toBe('const value = 2;');

    await session.shutdown();
    expect(server.shutdownRequested).toBe(true);
});

FakeLanguageServer answers the handshake with its capabilities (textDocumentSync: 2 by default), keeps the text of every open document the way a server does, and answers what handlers or handle(method, handler) registers. Anything else is refused as unsupported. A handler only answers; the capabilities must still declare the provider, since the session asks only what the server declares.

Member	What it does
`received`, `paramsOf(method)`	Every message that came in, and the params of one method
`documents`	The open documents with their `text`, `version` and `languageId`
`publishDiagnostics(uri, diagnostics, version?)`	Sends diagnostics
`notify(method, params?)`, `request(method, params?)`	Sends a notification or a request to the client
`crash()`	Closes the transport under the client
`shutdownRequested`, `exited`	Whether the client shut it down
`silent: true`	Never answers the handshake, like a server that hangs

For tests of editor features, FakeLanguageService skips the protocol and implements LanguageService directly.

Testing ​

Testing