dashboard/app: make it possible to test code that uses spanner

[dvyukov]

• tools/docker/env: add spanner emulator
• dashboard/app: make it possible to test code that uses spanner

[a-nogikh]

FWIW there's already syz-cluster code that interacts with the spanner emulator:
https://github.com/google/syzkaller/blob/master/syz-cluster/pkg/db/spanner.go#L138

I wonder if we can somehow reuse that instead of duplicating the functionality.

[tarasmadan]

And let me remind about the mocking code in case you'll find it useful: https://github.com/google/syzkaller/tree/master/pkg/coveragedb/mocks

[dvyukov]

And let me remind about the mocking code in case you'll find it useful: https://github.com/google/syzkaller/tree/master/pkg/coveragedb/mocks

No, I don't want to use mocks. With mocks:

1. I won't test actual SQL queries (high chances of errors b/c it's just text)
2. I won't test DDL statements used to setup database
3. code may work with mocks, but not in production, if mocks return the data tests want, so it's not really testing what I want
4. more code to write and tests are more fragile

Using the emulator solves all of the above.

[dvyukov]

FWIW there's already syz-cluster code that interacts with the spanner emulator: https://github.com/google/syzkaller/blob/master/syz-cluster/pkg/db/spanner.go#L138

I wonder if we can somehow reuse that instead of duplicating the functionality.

Ok, let's start with #6533 then ;)

[dvyukov]

FWIW there's already syz-cluster code that interacts with the spanner emulator: https://github.com/google/syzkaller/blob/master/syz-cluster/pkg/db/spanner.go#L138
I wonder if we can somehow reuse that instead of duplicating the functionality.

Done. Reused emulator start code and create instance/database from the existing code.
PTAL.