You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: collections_test.go
    path of file: ./repos/permify/pkg/database
    
    the code of the file until where you have to start completion: package database

import (
	"testing"

	"github.com/stretchr/testify/assert"

	base "github.com/Permify/permify/pkg/pb/base/v1"
)

func TestTupleCo
    
func TestSubjectCollection(t *testing.T) {
	// Create a new SubjectCollection with two subjects
	subject1 := &base.Subject{Type: "user", Id: "u1"}
	subject2 := &base.Subject{Type: "user", Id: "u2"}
	subjectColl := NewSubjectCollection(subject1, subject2)

	// Test the CreateSubjectIterator method
	iter := subjectColl.CreateSubjectIterator()
	assert.NotNil(t, iter)

	// Test the GetSubjects method
	subjects := subjectColl.GetSubjects()
	assert.Equal(t, 2, len(subjects))
	assert.Equal(t, subject1, subjects[0])
	assert.Equal(t, subject2, subjects[1])

	// Test the Add method
	subject3 := &base.Subject{Type: "user", Id: "u3"}
	subjectColl.Add(subject3)
	subjects = subjectColl.GetSubjects()
	assert.Equal(t, 3, len(subjects))
	assert.Equal(t, subject3, subjects[2])
}