zero-cost cloud emulation for Go

Test against real cloud SDKs without a real cloud.

Point the real AWS, Azure, and GCP Go SDKs at an in-memory server that speaks their wire protocols. Production code, unchanged. No mocks, no Docker, no bill.

Quick Start SDK-compat coverage

0 PROVIDERS0 DOMAINS0+ SERVICES2,400msreal cloud0 DEPS

01 · sdk-compat server

Don't rewrite your tests. Repoint them.

cloudemu speaks the real wire protocols — AWS Query/JSON/Smithy, Azure ARM, GCP REST — over a local httptest.NewServer. Switch the provider tab: the shape stays, one line changes.

no mocks to maintain
no Docker to babysit
no cloud accounts, no bill

Full coverage tables

aws_test.go

cloud := cloudemu.NewAWS()
ts := httptest.NewServer(awsserver.New(awsserver.Drivers{
    S3: cloud.S3, DynamoDB: cloud.DynamoDB, EC2: cloud.EC2,
}))
defer ts.Close()
 
// The REAL aws-sdk-go-v2 client — only the endpoint changes.
client := s3.NewFromConfig(cfg, func(o *s3.Options) {
    o.BaseEndpoint = aws.String(ts.URL)
    o.UsePathStyle = true
})
 
client.PutObject(ctx, &s3.PutObjectInput{ /* production code */ })

$

02 · why cloudemu

Three ways to test cloud code. One is free and instant.

Feature	Real cloud	LocalStack / emulators	cloudemu
Cost	$$$	$	Free
Speed	seconds	100ms+	~10ms
Works offline	✗	✓	✓
No Docker	✓	✗	✓
Setup	account + creds	Docker + config	go get
Realistic behavior	✓	◐	✓
Multi-cloud	✗	✗	✓
Real SDKs unchanged	✓	✓	✓

03 · beyond basic mocks

Behavior, not stubs.

Mocks return what you tell them to. cloudemu misbehaves like the real thing — lifecycle rules, throttling, injected outages, clock skew.

real_sdks
aws-sdk-go-v2, azure-sdk-for-go, and cloud.google.com/go drive an in-memory backend over their actual wire protocols. Nothing to mock, no call sites to rewrite.
chaos_engineering
Outages, latency spikes, probabilistic failures, throttling — in time-bounded windows. Your retry paths get exercised every run.
state_machines
VMs enforce real lifecycle transitions; illegal jumps return errors.
auto_metrics
Launching a VM pushes CPU, network, and disk metrics so alarms evaluate.
error_injection
Fail always, every Nth call, probabilistically, or the first N calls.
call_recording
Every call captured with inputs, outputs, errors, timing. Fluent asserts.
fake_clock
Deterministic TTL expiry, dedup windows, and alarm evaluation.
zero_deps
Pure Go standard library. Works anywhere Go runs.

04 · coverage

21 domains. 3 providers. All live.

sdk-compat + portable api

every domain is drivable two ways: the portable go api (in-process, no HTTP) or the sdk-compat server (real SDK clients over the wire).

05 · two surfaces

Same backend. Two ways in.

SDK-COMPAT SERVER

21 domains · real wire protocols

ts := httptest.NewServer(awsserver.New(drivers))
client := s3.NewFromConfig(cfg, func(o *s3.Options) {
    o.BaseEndpoint = aws.String(ts.URL)
})

Point the real SDK at a local endpoint. Your production code runs in tests exactly as it ships.

sdk-compat docs

PORTABLE GO API

21 domains · in-process, no HTTP

cloud := cloudemu.NewAWS()
cloud.S3.CreateBucket(ctx, "app-data")
cloud.S3.PutObject(ctx, "app-data", "cfg.yaml",
    []byte("port: 8080"), "text/yaml", nil)

Typed Go interfaces on the same backend — for setup code, assertions, and tests that skip HTTP altogether.

portable api docs

get started

One `go get` from now, your tests stop needing the internet.

go get github.com/stackshy/cloudemu/v2

Read the docs Quick Start

MIT license · Go 1.25+ · zero dependencies