The Email Customizer for WooCommerce  suggest several ways for testing your template :

1. Send Test Email 

Our plugin uses wp_mail function for sending emails. If you want to test your email template, you need correct configure your wp_mail. With the help of some plugins you can do it very easily. For example, WP Mail SMTP plugin

2. Email Preview

This feature helps you test your email without sending any email. 

More information: How to use Email Preview?

3. Export Template and test it manually

You can download your template as a HTML and test it any browser or send it manually to some email address for testing. You can find export functionality on the top right menu second option. 

You do not need to waste your time sending emails and control them. If you want to see the final version of your template please click the Preview button from the top right menu.

Note: Preview shows the final version of your template. If you turn off the replace email functionality, in this case, you will see the default email template. Before checking the Email Preview, make sure that you enable replace email functionality. 

More information about enabling/disabling email customizing in Email Customizer: How to enable email customizing?

By default, after activating the Email Customizer, it will customize all email types automatically.

If you want to disable it for a while, you can turn off it. For example, you have a live website and you want to create your templates, then test them. No problem, it is so easy. In this case, you need just switch off replace email feature. When creating templates just enable it and enjoy your emails.

This feature located in the settings tab -> general settings section . 

The plugin gives you 2 opportunity:

1. Enable/disable specific email type. For doing it you need select email type from dropdown then navigate to settings. 

2. Enable/disable all email types at once. For doing it you need just navigate to settings.