for this question im working with prisma's dev container: https://github.com/prisma/prisma/tree/main/.devcontainer
once i open that repo inside of a container using the remote container plugin in visual studio and run some Jest Tests that rely on docker services defined in the https://github.com/prisma/prisma/tree/main/docker folder, i get the error of "cant connect to database" for all databases...
it's like if the dev container had no idea those services exist... on my pc, looking at docker desktop i see the services up and running but the devcontainer can't... why?
i find it weird that i had to change any type of setting since this files are from the prisma repo, they are suposed to be ready for action once downloaded... right?
Assumming the docker network driver is bridge (Default).
If the script is runing this line to get env in your devcontainer as below.
const connectionString = (
process.env.TEST_MYSQL_URI_MIGRATE || 'mysql://root:root@localhost:3306/tests-migrate'
).replace('tests-migrate', 'tests-migrate-dev')
`
The localhost in the connection string means the localhost in your devcontainer but not your host machine.
You should access the localhost of your host machine instead.
The fix is set the TEST_MYSQL_URI_MIGRATE environment variable instead like
TEST_MYSQL_URI_MIGRATE=mysql://root:root@host.docker.internal:3306/tests-migrate
For the details how to access the localhost of host machine, please read this question