env GO111MODULE=on

go list -f '{{.TestImports}}'
stdout net/http # from .TestImports

go list -test -f '{{.Deps}}'
stdout golang_org/x/crypto # dep of .TestImports

-- go.mod --
module m

-- x.go --
package x

-- x_test.go --
package x
import "testing"
import _ "net/http"
func Test(t *testing.T) {}