Golang: Integration tests hitting the same db instance even upon db.Close() - sqlite

Question

I have a test suite that uses an in-memory sqlite instance to run db queries. After adding some tests, I suddenly started to get tons of "UNIQUE constraint failed..." errors in every line that tries to perform an insertion. That makes it seem like all my tests are connecting to, writing to, and reading from the same db instance. Here's how the test db instance is produced
const DBProvider = "sqlite3"
// DBConnection is the connection string to use for testing
const DBConnection = "file::memory:?cache=shared"
// NewMigratedDB returns a new connection to a migrated database
func NewMigratedDB(provider string, connection string, models ...interface{}) (*gorm.DB, error) {
db, err := gorm.Open(provider, connection)
if err != nil {
return nil, err
}
db = db.AutoMigrate(models...)
if db.Error != nil {
return nil, err
}
return db, nil
}
And here's how it's used in tests -
db, err := test.NewMigratedDB(test.DBProvider, test.DBConnection, models...)
defer db.Close()
// read/write anything
How can I make each call to NewMigratedDB to produce a different instance of SQLite that only listens to queries from the unit test that instantiated it

Answer 1

First of all, it would be helpful to see a full example of how you're using NewMigratedDB in a test. Here's my suggestions based on what I can see (and what I can't).
Setup a Named In-memory Database
Each of your unit tests appear to be using the same in-memory copy of the SQLite database. Use the following syntax to create separate named instances of the in-memory database. If your tests are running in parallel, they'd most likely share the same database. Replace test1 with a unique name for each test that is running in parallel (see the sqlite documentation for more info).
If two or more distinct but shareable in-memory databases are needed in a single process, then the mode=memory query parameter can be used with a URI filename to create a named in-memory database
const DBConnection = "file:test1?mode=memory&cache=shared"
Open and Close Between Tests
You also need to make sure you're initializing a fresh database per-test, not once at the top of your testing function. For example:
func TestSomething(t *testing.T) {
// Don't initialize it here
t.Run("test1", func(t *testing.T) {
db, err := test.NewMigratedDB(test.DBProvider, test.DBConnection, models...)
defer db.Close()
// Do something
})
t.Run("test2", func(t *testing.T) {
db, err := test.NewMigratedDB(test.DBProvider, test.DBConnection, models...)
defer db.Close()
// Do something
})
}
If you are opening and closing before and after each test and you do not have any tests running concurrently that also connect to sqlite, then closing the connection should clear the sqlite database and you don't need to use named, in-memory databases as a fresh database will be re-created on the next call to gorm.Open. There's a lot of "ifs" there so pick your poison.