You can test your activity within Lumière directly from an Activity's Design page by clicking the "Preview" button at the bottom of the page.  You'll be taken to the participant screen for your activity.  For testing your activity while integrating with third-party software via passthrough, see integrating Lumière with other surveys and workflows.

Alternatively, you can preview an activity by clicking on the preview icon (eye) that appears when hovering over activity tiles on the My Activities page.

Note: While previewing your activity in test mode, any data you enter will not be included in outputs the Insights page and your session will not be included the activity statistics.