Mocking AWS SDK

main.go

package main

import (
	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/service/organizations"
	"github.com/aws/aws-sdk-go/service/organizations/organizationsiface"
)

type Organizations struct {
	Client organizationsiface.OrganizationsAPI
}

func (s *Organizations) ListAccounts(in *organizations.ListAccountsInput) (*organizations.ListAccountsOutput, error) {
	result, err := s.Client.ListAccounts(in)
	return result, err
}

func WhatAreMyAccounts(client *Organizations) (*organizations.ListAccountsOutput, error) {
	return client.ListAccounts(
		&organizations.ListAccountsInput{
			MaxResults: aws.Int64(5),
			NextToken:  nil,
		},
	)
}

main_test.go

package main

import (
	"testing"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/service/organizations"
	"github.com/aws/aws-sdk-go/service/organizations/organizationsiface"
	"github.com/stretchr/testify/assert"
)

type MockedOrganizations struct {
	organizationsiface.OrganizationsAPI
}

func (m *MockedOrganizations) ListAccounts(in *organizations.ListAccountsInput) (*organizations.ListAccountsOutput, error) {
	return &organizations.ListAccountsOutput{
		Accounts: []*organizations.Account{
			{
				Arn:   aws.String(""),
				Email: aws.String("test1@example.com"),
				Id:    aws.String("234567890"),
				Name:  aws.String("test-1"),
			},
			{
				Arn:   aws.String(""),
				Email: aws.String("test2@example.com"),
				Id:    aws.String("123456789"),
				Name:  aws.String("test-2"),
			},
		},
	}, nil
}

func TestListAccounts(t *testing.T) {
	test := Organizations{
		Client: &MockedOrganizations{},
	}
	resp, err := WhatAreMyAccounts(&test)
	assert.Equal(t, len(resp.Accounts), 2)
	assert.NoError(t, err)
}