test(cli): add tests for stdin input (#107)

* test(cli): add tests for stdin input

* test(cli): extract mock stdin to helper function

* test(cli): add comprehensive tests for stdin edge cases and output file handling

* refactor(test): streamline mockStdin function and relocate to utils

* test(cli): remove redundant test for JSON encoding from stdin

* test(cli): restore mocks consistently

* test(cli):  restructured output file tests and modified some assertions

* chore: fix linting issues & remove redundant cleanups

---------

Co-authored-by: mad-cat-lon <113548315+mad-cat-lon@users.noreply.github.com>
Co-authored-by: Johann Schopplich <mail@johannschopplich.com>

packages/cli/test/utils.ts

@@ -2,6 +2,7 @@ import * as fsp from 'node:fs/promises'
 import * as os from 'node:os'
 import * as path from 'node:path'
 import process from 'node:process'
+import { Readable } from 'node:stream'
 import { runMain } from 'citty'
 import { mainCommand } from '../src/index'
 
@@ -76,3 +77,20 @@ async function writeFiles(baseDir: string, files: FileRecord): Promise<void> {
     }),
   )
 }
+
+export function mockStdin(input: string): () => void {
+  const mockStream = Readable.from([input])
+
+  const originalStdin = process.stdin
+  Object.defineProperty(process, 'stdin', {
+    value: mockStream,
+    writable: true,
+  })
+
+  return () => {
+    Object.defineProperty(process, 'stdin', {
+      value: originalStdin,
+      writable: true,
+    })
+  }
+}