test: test stopPreviousClient behavior

Author: seanwu1105

src/test/assets/filename with spaces.txt renamed to python/tests/assets/filename with spaces.txt

@@ -134,8 +134,7 @@ type CreateClientArgs = {
   readonly outputChannel: OutputChannel
 }
 
-// TODO: Unit test this behavior.
-function stopPreviousClient() {
+export function stopPreviousClient() {
   return (source$: Observable<LanguageClient | undefined>) =>
     source$.pipe(
       startWith(undefined),

src/qmlls/client.ts

@@ -0,0 +1,45 @@
+import * as assert from 'node:assert'
+import type { Subscription } from 'rxjs'
+import { ReplaySubject } from 'rxjs'
+import * as sinon from 'sinon'
+import { LanguageClient } from 'vscode-languageclient/node'
+import { stopPreviousClient } from '../../../qmlls/client'
+import { waitFor } from '../test-utils'
+
+suite('qmlls/client', () => {
+  suite('stopPreviousClient', () => {
+    suite('when a new client is created', () => {
+      const client$ = new ReplaySubject<LanguageClient>(1)
+      const observable$ = client$.pipe(stopPreviousClient())
+
+      const client1 = new LanguageClient(
+        'client1',
+        { command: 'mock-command' },
+        {},
+      )
+      const client2 = new LanguageClient(
+        'client2',
+        { command: 'mock-command' },
+        {},
+      )
+
+      let disposeSpy: sinon.SinonSpy
+      let subscription: Subscription
+
+      setup(() => {
+        disposeSpy = sinon.spy(client1, 'dispose')
+        subscription = observable$.subscribe()
+        client$.next(client1)
+        client$.next(client2)
+      })
+
+      teardown(() => {
+        subscription.unsubscribe()
+        sinon.restore()
+      })
+
+      test('should stop previous client', async () =>
+        waitFor(() => assert.ok(disposeSpy.calledOnce)))
+    })
+  })
+})

src/test/mocks/extension.ts

@@ -3,6 +3,7 @@ import * as path from 'node:path'
 import * as process from 'node:process'
 import type { RunResult } from '../../run'
 import { run, wrapAndJoinCommandArgsWithQuotes } from '../../run'
+import { TEST_ASSETS_PATH } from './test-utils'
 
 suite('run', () => {
   let result: RunResult
@@ -19,8 +20,8 @@ suite('run', () => {
     () => {
       setup(async () => {
         const filePath = path.resolve(
-          __dirname,
-          '../../../src/test/assets/filename with spaces.txt',
+          TEST_ASSETS_PATH,
+          'filename with spaces.txt',
         )
 
         if (process.platform === 'win32')