Package not usable with parallel tests

[jnwhiteh]

There is currently a data race when using go-sqlmock in two tests in parallel due to the way the API is currently designed. There is only ever one "mock" database and all operations are done on this. This means two tests cannot use this package in parallel. This is evidenced from the following data race in a package I am developing. I'm going to take a stab and changing the API to accommodate this.

==================
WARNING: DATA RACE
Read by goroutine 10:
  github.com/DATA-DOG/go-sqlmock.ExpectQuery()
      /Users/jnwhiteh/go/src/github.com/DATA-DOG/go-sqlmock/sqlmock.go:155 +0x138
  github.com/jnwhiteh/migration.setupVersioned()
      /Users/jnwhiteh/go/src/github.com/jnwhiteh/migration/migration_test.go:35 +0x22a
  github.com/jnwhiteh/migration.TestDowngradesUnsupported()
      /Users/jnwhiteh/go/src/github.com/jnwhiteh/migration/migration_test.go:61 +0x73
  testing.tRunner()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:422 +0x10f

Previous write by goroutine 8:
  github.com/DATA-DOG/go-sqlmock.(*conn).Close()
      /Users/jnwhiteh/go/src/github.com/DATA-DOG/go-sqlmock/connection.go:24 +0x266
  database/sql.(*driverConn).finalClose()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/database/sql/sql.go:310 +0x175
  database/sql.finalCloser.(database/sql.finalClose)·fm()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/database/sql/sql.go:398 +0x57
  database/sql.(*DB).Close()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/database/sql/sql.go:487 +0x6fa
  github.com/jnwhiteh/migration.TestFailingToGetCurrentVersion()
      /Users/jnwhiteh/go/src/github.com/jnwhiteh/migration/migration_test.go:54 +0x331
  testing.tRunner()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:422 +0x10f

Goroutine 10 (running) created at:
  testing.RunTests()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:504 +0xb46
  testing.Main()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:435 +0xa2
  main.main()
      github.com/jnwhiteh/migration/_test/_testmain.go:61 +0xdc

Goroutine 8 (finished) created at:
  testing.RunTests()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:504 +0xb46
  testing.Main()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:435 +0xa2
  main.main()
      github.com/jnwhiteh/migration/_test/_testmain.go:61 +0xdc
==================
==================
WARNING: DATA RACE
Write by goroutine 10:
  github.com/DATA-DOG/go-sqlmock.ExpectQuery()
      /Users/jnwhiteh/go/src/github.com/DATA-DOG/go-sqlmock/sqlmock.go:156 +0x309
  github.com/jnwhiteh/migration.setupVersioned()
      /Users/jnwhiteh/go/src/github.com/jnwhiteh/migration/migration_test.go:35 +0x22a
  github.com/jnwhiteh/migration.TestDowngradesUnsupported()
      /Users/jnwhiteh/go/src/github.com/jnwhiteh/migration/migration_test.go:61 +0x73
  testing.tRunner()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:422 +0x10f

Previous write by goroutine 8:
  github.com/DATA-DOG/go-sqlmock.(*conn).Close()
      /Users/jnwhiteh/go/src/github.com/DATA-DOG/go-sqlmock/connection.go:25 +0x2d0
  database/sql.(*driverConn).finalClose()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/database/sql/sql.go:310 +0x175
  database/sql.finalCloser.(database/sql.finalClose)·fm()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/database/sql/sql.go:398 +0x57
  database/sql.(*DB).Close()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/database/sql/sql.go:487 +0x6fa
  github.com/jnwhiteh/migration.TestFailingToGetCurrentVersion()
      /Users/jnwhiteh/go/src/github.com/jnwhiteh/migration/migration_test.go:54 +0x331
  testing.tRunner()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:422 +0x10f

Goroutine 10 (running) created at:
  testing.RunTests()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:504 +0xb46
  testing.Main()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:435 +0xa2
  main.main()
      github.com/jnwhiteh/migration/_test/_testmain.go:61 +0xdc

Goroutine 8 (finished) created at:
  testing.RunTests()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:504 +0xb46
  testing.Main()
      /usr/local/Cellar/go/1.3.3/libexec/src/pkg/testing/testing.go:435 +0xa2
  main.main()
      github.com/jnwhiteh/migration/_test/_testmain.go:61 +0xdc
==================
PASS
Found 2 data race(s)
exit status 66
FAIL    github.com/jnwhiteh/migration   1.105s

[l3pp4rd]

Hi, yes indeed, currently the api is designed to use one mock connection, that could be improved without interfering with the public interface. In meantime, I cannot promise to take a look soon, but if you are working in this area, would be great if you could submit a pull request. cheers

[wongak]

@jnwhiteh Could you do me a favor and see if my PR would solve your problem? If you are also tackling this issue: what approach did you take? Cheers

[jnwhiteh]

@wongak I added some comments to your pull request, lets continue that discussion there. If useful, I can share the branch I'm working on.

[l3pp4rd]

thanks @jnwhiteh and @wongak for the discussion and your branch to support concurrency. The refactor branch is now covering all the issues which the library had in initial version. It will be merged as soon as the README and examples are updated, cheers

[jnwhiteh]

Thanks for the update!