Add integration tests for spanner

[dhui]

Is your feature request related to a problem? Please describe.
The spanner db driver should have integration tests to prevent regressions

Describe the solution you'd like
Use the spanner emulator which is available with pre-built docker images

Describe alternatives you've considered

• Use in-memory emulator written in Go directly
  • Would probably startup faster than a docker image but not sure about the differences between the emulators

Additional context
N/A

[wyardley]

I've done some things similar to this in Circle, and I can see where the integration test code is happening.

Looks like I'd use your docker testing framework for this part vs. the way the existing integration test is handled, right?

[dhui]

The current spanner tests aren't run in CI since they're tagged as short. This change would involve using either using docker images or the in-memory emulator in the tests. The main advantage of using the docker image is that we can test against different versions of the spanner emulator which in theory, reflect the different versions of spanner.

[dhui]

Fixed in master. We're using the in-memory emulator directly.