Exporting Golang packages for testing?

Question

In trying to come with test against code that uses the following struct:

type DatabaseSt struct {
    DBName            string
    DBConnectionStr   string
    dbConnection      *sql.DB
    InterpolateParams bool

    //Archived Databases
    MinFinancialYear int
    MaxFinancialYear int
}

//DatabaseContext The context to use if the use of a database is needed.
type DatabaseContext struct {
    *Context
    Database DatabaseSt
}

I stumbled upon this Medium article claiming that you can export Golang packages, with their internals, in test code. Unfortunately, I'm not sure what they mean in their last words:

export_test.go only be include when we run go test, so it not pollute your API, and user never access them(not like java's @VisibleForTesting), and it build a bridge let unexported one accessible in math_test

and even worse, replication of it leads to nowhere fast:

/* Here, context is the package containing the struct I want full access to */

I basically need to be able to set the dbConnection of that DatabaseSt for testing, without modifying the source code.

Answer 1

Add the following file named export_test.go:

package context

func SetDbConnection(DatabaseSt *ds, db *sql.DB) {
    ds.dbConnection = db
}

Use it from other test files in the same directory like this:

package context_test

import "context"

func FooTest(t *testing.T) {
     ...
     context.SetDbConnection(ds, db)
     ...
}

Alternatively, write the test in the context package so you have full access to the members:

package context

func FooTest(t *testing.T) {
     ...
     ds.dbConnection = db
     ...
}