When I try to run 'anchor test' (on Ubuntu 20.04.1) following this tutorial https://dev.to/edge-and-node/the-complete-guide-to-full-stack-solana-development-with-react-anchor-rust-and-phantom-3291
I get this error on a new project:
Error: Your configured rpc port: 8899 is already in use
I can't find a solution online - I found this but it doesn't explain what went wrong and their solution also doesn't help: https://forums.solana.com/t/unable-test-the-solana-program-your-configured-rpc-port-8899-is-already-in-use/7745
I've tried rebooting Ubuntu and it doesn't help.
Why is this happening and how can I fix it?
This only seems to happen if
solana-test-validator is running. Why would that be?