With an open exercise type, you can use Test Scenarios. A scenario is a list of answers that will be available in the author preview. You can run the scenario by clicking the red button in the top left. It will send all the answers to the server one by one and show the response.
Answers must be in Math presentation format (TeX or asciimathml), like described here. When no delimiters are used, hash tags are used by default. Variables also work in the Test scenario.