Deflake settings persistence desktop test by verifying we have written to the disk before continuing (#4349)

e2e/playwright/testing-settings.spec.ts

@@ -266,10 +266,15 @@ test.describe('Testing settings', () => {
         process.platform === 'win32',
         'TODO: remove this skip https://github.com/KittyCAD/modeling-app/issues/3557'
       )
-      const { electronApp, page } = await setupElectron({
+      const projectName = 'bracket'
+      const {
+        electronApp,
+        page,
+        dir: projectDirName,
+      } = await setupElectron({
         testInfo,
         folderSetupFn: async (dir) => {
-          const bracketDir = join(dir, 'bracket')
+          const bracketDir = join(dir, projectName)
           await fsp.mkdir(bracketDir, { recursive: true })
           await fsp.copyFile(
             executorInputPath('focusrite_scarlett_mounting_braket.kcl'),
@@ -281,6 +286,11 @@ test.describe('Testing settings', () => {
       await page.setViewportSize({ width: 1200, height: 500 })
 
       // Selectors and constants
+      const tempSettingsFilePath = join(
+        projectDirName,
+        projectName,
+        PROJECT_SETTINGS_FILE_NAME
+      )
       const userThemeColor = '120'
       const projectThemeColor = '50'
       const settingsOpenButton = page.getByRole('link', {
@@ -312,6 +322,13 @@ test.describe('Testing settings', () => {
         await themeColorSetting.fill(projectThemeColor)
         await expect(logoLink).toHaveCSS('--primary-hue', projectThemeColor)
         await settingsCloseButton.click()
+        // Make sure that the project settings file has been written to before continuing
+        await expect
+          .poll(async () => fsp.readFile(tempSettingsFilePath, 'utf-8'), {
+            message: 'Setting should now be written to the file',
+            timeout: 5_000,
+          })
+          .toContain(`themeColor = "${projectThemeColor}"`)
       })
 
       await test.step('Refresh the application and see project setting applied', async () => {