If the test you have added to the class has not been started by any students(including demo students), you can remove it from the class.
Removing a Test from a Class:
1. Login to the site and select your Instructor role.
2. From your Instructor home page, you will click on the class name. Then click the Edit Class button.
3. Select the Tests tab.
4. Locate the exam you would like to remove. If no students have started the test there will be a remove button to the right of the test name. Click that, and the test will have been removed from your class.
If students have started the test you cannot remove the test, the remove button will be gone. You can edit the test settings and change the end date/time to the past to prevent more students from taking the test. Click the Edit button and update your settings.
You can also hide the grade from the grade book so the test will not affect the student's overall grade. More information on hiding grades can be found here.