use absolute paths

standalone-cli/tests/test.js

@@ -1,3 +1,4 @@
+const path = require('path')
 const { execSync } = require('child_process')
 const os = require('os')
 const fs = require('fs-extra')
@@ -34,11 +35,16 @@ it('supports first-party plugins', () => {
 
 it('supports postcss config files', async () => {
   // We have to run this test outside of any place with node_modules for it to properly test this situation
-  let result = await inIsolatedContext(() => {
+  let result = await inIsolatedContext((base) => {
     // Emulate the user adding their own postcss plugins
     execSync(`npm install postcss-will-change`)
 
-    return exec('--content tests/fixtures/basic.html --postcss tests/fixtures/postcss.config.js')
+    return exec(
+      `--content ${path.resolve(base, 'tests/fixtures/basic.html')} --postcss ${path.resolve(
+        base,
+        'tests/fixtures/postcss.config.js'
+      )}`
+    )
   })
 
   expect(result).toContain('.uppercase')
@@ -51,7 +57,7 @@ it('supports postcss config files', async () => {
 /**
  * @template T
  * @param {() => T} fn
- * @returns {T}
+ * @returns {Promise<T>}
  */
 async function inIsolatedContext(fn) {
   // Create a new directory entirely outside of the package for the test
@@ -73,7 +79,7 @@ async function inIsolatedContext(fn) {
   process.chdir(dest)
 
   try {
-    return await fn()
+    return await fn(dest)
   } finally {
     // Change back to the original working directory
     process.chdir(__dirname)