Operations on go-sqlmock.Driver fail with: expected a connection to be available, but it is not

[fho]

Hello,

I'm working on a package that wraps an sql.Driver and adds functionality. To test it, I'm trying to use go-sqlmock. I'm running into the issue that if I wrap the go-sqlmock Driver, all operations fail with the error: expected a connection to be available, but it is not

I'm accessing the driver via:

db, _, _ := sqlmock.New()
db.Driver()

This can be reproduced e.g. via sqlmw:

package dddbmock_test

import (
    "database/sql"
    "testing"

    "github.com/DATA-DOG/go-sqlmock"
    "github.com/ngrok/sqlmw"
)

func TestMWWrap(t *testing.T) {
    db, _, err := sqlmock.New()
    if err != nil {
        t.Fatal("sqlmock new failed:", err)
    }

    sql.Register(
        "mwdriver",
        sqlmw.Driver(db.Driver(), &sqlmw.NullInterceptor{}),
    )

    db, err = sql.Open("mydriver", "")
    if err != nil {
        t.Fatal("opening driver failed:", err)
    }

    if err := db.Ping(); err != nil {
        t.Error("ping failed", err)
    }
}

Without using other external packages and mimicking the wrapping behavior instead it can be reproduced like:

package dddbmock_test

import (
    "database/sql"
    "testing"

    "github.com/DATA-DOG/go-sqlmock"
)

func TestRegister(t *testing.T) {
    db, _, err := sqlmock.New(sqlmock.MonitorPingsOption(true))
    if err != nil {
        t.Fatal("sqlmock new failed:", err)
    }

    sql.Register("mydriver", db.Driver())

    db, err = sql.Open("mydriver", "")
    if err != nil {
        t.Fatal("opening driver failed:", err)
    }

    if err := db.Ping(); err != nil {
        t.Error("ping failed", err)
    }

    if _, err := db.Exec(""); err != nil {
        t.Error("exec failed", err)
    }
}

The comment https://github.com/DATA-DOG/go-sqlmock/issues/83#issuecomment-582962456 seems to be about the same issue. I guess it's not intended to be used like that, but it would be awesome to support operations on the go-sqlmock Driver.

[l3pp4rd]

Hi, maybe you are willing to contribute this patch? Haven’t used golang for more than a year, would be difficult to find a willing to

[fho]

@l3pp4rd depends on the effort :-). I ended up writing my own simple mock instead, that works okayish for my current usecase. Do you maybe have an idea what the cause it how it could be fixed?

[dolmen]

The first code has a typo in the driver name: mwdriver vs mydriver.

[dolmen]

Here is a hack (unsupported): use the internal DSN:

db, err = sql.Open("mydriver", "sqlmock_db_0")

Example on the Go Playground