There are a couple of different places to test workflows. The workflow builder and a workflow run both have options to Run trees without creating a form submission. Using the options detailed below can save you time in testing.
Inputs are the data that's used when workflow is run. They're based on the source, and can be anything from a key value used for lookup, to an extensive json string used for all the parameters.
For testing workflows against a standard set of data, you can re-use input values for multiple workflow runs. And, since inputs are just text, you can alter the inputs as needed to easily create different inputs for workflows.
Inputs are available to copy from the Run console in the Task Engine. If you want to use the inputs from a particular workflow run, you can select Run Again from that workflow run and those inputs will automatically be entered.
When you select the Run or Run Again options (see below), you can type or paste your inputs into the Source Data field.
Task Results are the values returned by nodes (handlers) in a workflow. They are normally used by nodes farther down a workflow. Similarly to inputs, they can be updated to test multiple options for a run. Note that all updates to task results are audited.
Being able to run and re-run a workflow as needed is the most powerful option for testing workflows available. There are two different places where this option is available.
From the workflow builder, Run is one of the options in the Actions drop-down.
Run (Run Again) is also an option on the Actions button from within a Run itself.
Errors are a part of any testing. A more comprehensive article on errors is available here