func TestBadPayload(t *testing.T) {
	assert := assert.New(t)
	payload := Payload{}
	assert.Equal("null", payload.String())
}
TestBadPayload checks that error handling is working.
package tracker
import (
	"testing"
	"github.com/stretchr/testify/assert"
)
func TestAdd(t *testing.T) {
	assert := assert.New(t)
	payload := *InitPayload()
	payload.Add("e", NewString("pv"))
	assert.Equal(1, len(payload.Get()))
	assert.Equal("pv", payload.Get()["e"])
	assert.Equal("{\"e\":\"pv\"}", payload.String())
	payload.Add("e", NewString("ue"))
	assert.Equal(1, len(payload.Get()))
	assert.Equal("ue", payload.Get()["e"])
	assert.Equal("{\"e\":\"ue\"}", payload.String())
	payload.Add("empty", NewString(""))
	assert.Equal(1, len(payload.Get()))
	payload.Add("", NewString("pv"))
	assert.Equal(1, len(payload.Get()))
	payload.Add("", nil)
	assert.Equal(1, len(payload.Get()))
}