How to handle JustOn test class errors during custom development?
Depending on your business requirements, your system setup may involve some custom development and corresponding tests in a sandbox.
Info
JustOn recommends to create the sandbox copy of your production org after JustOn is set up, as explained in Why install and configure JustOn in a production org.
JustOn recommends to run only your test classes during your custom development. To this end, you select the test level RunLocalTests. This will execute all tests in your org, except for tests from managed packages – which is the default for production deployments that involve Apex classes.
You may also execute the test classes that are delivered with the JustOn package. These test classes, however, are designed to cover the standard JustOn development and may fail in your customized system.
These errors are not indicative of your actual environment, so you can just ignore them.
Related information:
Why install and configure JustOn in a production org?
Get Started with Apex Unit Tests on Salesforce Trailhead
Add a Test Class in the Salesforce Developer Documentation
testLevel Deployment Option in the Salesforce Developer Documentation