Unit Test should be such that they are self dependent and not dependent on the external systems / integrations to verify the accuracy of the unit function and logic. Hence many a times we mock the external applications / service call so that they are not dependent.
Many a times Junit would pass even if we are making actual service calls and just verifying if the calls are being made. In those cases , though your Junit may work fine today but will create problem once those services , applications won't be active. In such situation all Junits would fail and will give a wrong picture about the logic consistency of your code units.
So, How to make sure that all service / external application calls have been mocked ?
Step 1 - Make sure that no application / Services are running on your Machine.
Step 2 - Stop all Servers in your workspace.
Step 3 - Disconnect your network cable so that it shouldn't make any call over network.
Step 4 - Execute your Junits again and see the result.
All Junits still passing will make sure that all Junits are self dependent.