test: use sleep inside the mock for lsp process

test/helpers.ts

@@ -45,8 +45,17 @@ export function createFakeEditor(path?: string): TextEditor {
   return editor
 }
 
+/** A function that sleeps for a preiod of `ms` and the resolves the given value */
+function sleep<T>(resolveValue: T, ms: number) {
+  return new Promise<T>((resolve) => {
+    setTimeout(() => resolve(resolveValue), ms)
+  })
+}
+
 export function createFakeLanguageServerProcess(): LanguageServerProcess {
-  spawn("lsp").exit(0).stdout("hello from lsp")
+  spawn("lsp")
+    .exit(() => sleep(0, 1000))
+    .stdout("hello from lsp")
   // eslint-disable-next-line @typescript-eslint/no-var-requires
   return require("child_process").spawn("lsp")
 }