Mock Engine

Mock Engine — Local Development Mock Environment Management

Provides unified mock infrastructure (MySQL, Redis, Kafka, MQTT, LocalStack, WireMock) via Docker Compose, supporting local development and integration testing.

Description

Applicable scenarios:

• Start/stop mock environment: make mock-up one-command launch of all dependency services
• Load test data: Base fixtures auto-load; scenario fixtures load on demand
• Create test scenarios: Prepare preset data (SQL + Redis + WireMock stubs) for specific business flows
• Troubleshoot startup issues: Container status checks, port conflicts, data loading failures
• Integration testing: Manage mock infrastructure in automated tests via Java SDK or Go SDK

Prerequisites:

• Docker Compose v2.20+ (verify with docker compose version)
• A mock/ directory exists at the project root (containing docker-compose.yml and Makefile)
• If there is no mock/ directory, initialize from the mock-engine template:

  cp -r /path/to/mock-engine/core/templates/mock/ ./mock/
  # Modify project configuration in mock/Makefile (database name, password, etc.)
  

Rules

Operational Flow

First-time initialization:

cd mock/
make mock-init    # Download compose fragments

Start Mock environment:

make mock-up      # Start all services + wait for health checks + load data
make mock-status  # Verify all services are running normally

Start the application (backend-service example):

# The appName environment variable must be set
appName=your-app mvn spring-boot:run \
  -pl your-app \
  -Dspring-boot.run.profiles=dev-local,mock

Load a test scenario:

make mock-scenario SCENARIO=user-registration
# View available scenarios:
ls fixtures/scenarios/

Stop/reset:

make mock-down    # Stop services (preserve data)
make mock-clean   # Stop + delete data volumes
make mock-reset   # Full reset (clean + init + up)

Default Port Mapping

Test Data Management

Base Fixtures (auto-loaded): Place in mock/fixtures/base/, executed in filename order:

fixtures/base/
├── 01-seed-users.sql        # INSERT test users
├── 02-seed-devices.sql      # INSERT test devices
└── 03-seed-data.sql         # INSERT test data

Scenario Fixtures (load on demand): One subdirectory per scenario:

fixtures/scenarios/user-registration/
├── data.sql                 # MySQL data
├── redis-cmds.txt           # Redis CLI commands (one per line)
└── stubs-override/          # WireMock stub overrides

redis-cmds.txt format:

# Comment line
SET user:1001:token abc123
HSET device:DEV001 status online
EXPIRE user:1001:token 3600

WireMock Stubs: Place in mock/stubs/<service-name>/:

{
  "request": {
    "method": "POST",
    "urlPath": "/stripe/v1/customers"
  },
  "response": {
    "status": 200,
    "jsonBody": { "id": "cus_mock_001" }
  }
}

Supports advanced features: conditional routing (queryParameters/bodyPatterns), dynamic templates (response-template), state machines (scenarioName), Webhook callbacks (serveEventListeners).

Common Troubleshooting

MySQL connection failed:

docker ps --filter name=mock-mysql
docker logs mock-mysql
docker exec -e MYSQL_PWD=root123456 mock-mysql mysql -uroot -e "SELECT 1"

Bind mount not taking effect (Docker-in-Docker): SQL files not auto-loaded into MySQL:

docker exec -e MYSQL_PWD=root123456 -i mock-mysql mysql -uroot < mock/sql/init-schema.sql

WireMock stubs not loaded:

curl http://localhost:19999/__admin/mappings | python3 -m json.tool
docker cp mock/stubs/. mock-wiremock:/home/wiremock/mappings/
curl -X POST http://localhost:19999/__admin/mappings/reset

Spring Bean missing (CloudBeanCondition): Ensure the appName=your-app environment variable is set.

SDK Integration (Automated Testing)

Java (Testcontainers):

// pom.xml: <dependency>com.example:mock-engine</dependency>
MockInfraManager manager = MockInfraManager.fromProjectMockDir("./mock");
manager.startAll();
Map<String, String> props = manager.getAllProperties();

Go:

// go.mod: require gitlab.example.com/tools/mock-engine/go
infra := mockinfra.New(mockinfra.WithProjectDir("./mock"))
infra.Start(ctx)
defer infra.Stop(ctx)
infra.LoadScenario(ctx, "user-registration")

Examples

Bad Example

User: Help me start the mock environment
AI: Let me just docker compose up directly

docker compose up -d

# Then directly start the application
mvn spring-boot:run -pl your-app

Problems:

• Did not enter the mock/ directory
• Did not use make mock-init to initialize fragments
• Did not use make mock-up (skips health checks and data loading)
• Did not set appName environment variable or mock profile

Good Example

User: Help me start the mock environment
AI: OK, let me check the mock directory and start the environment.

cd mock/
# Check if already initialized
ls .fragments/Makefile.include 2>/dev/null || make mock-init
# Start and wait for all services to be ready
make mock-up
# Verify service status
make mock-status

# Start the application (with correct environment variable and profile)
cd ..
appName=your-app mvn spring-boot:run \
  -pl your-app \
  -Dspring-boot.run.profiles=dev-local,mock

# Verify health check
curl -s http://localhost:7777/actuator/health

Bad Example

User: I need to test the user registration flow
AI: Let me just call the registration API directly

curl -X POST http://localhost:7777/account/register \
  -H "Content-Type: application/json" \
  -d '{"email":"newuser@test.com"}'

Problems:

• Did not load the test scenario data first
• Did not provide an Authorization token
• Missing required request parameters

Good Example

User: I need to test the user registration flow
AI: OK, let me load the registration test scenario data first, then test step by step.

# 1. Load user registration scenario data
cd mock/
make mock-scenario SCENARIO=user-registration

# 2. Login first to get an admin token
TOKEN=$(curl -s -X POST http://localhost:7777/account/login \
  -H "Content-Type: application/json" \
  -d '{"email":"testuser1@mock.local","password":"password","loginType":99}' \
  | python3 -c "import sys,json; print(json.load(sys.stdin)['data']['token'])")

# 3. Check if the email is available
curl -s -X POST http://localhost:7777/account/check-email \
  -H "Content-Type: application/json" \
  -H "Authorization: $TOKEN" \
  -d '{"email":"newuser@mock.local"}'

# 4. Execute registration
curl -s -X POST http://localhost:7777/account/register \
  -H "Content-Type: application/json" \
  -H "Authorization: $TOKEN" \
  -d '{"email":"newuser@mock.local","password":"Test@1234","nickname":"TestUser"}'

Related Resources

• mock-engine repository: gitlab.example.com/tools/mock-engine
• Design document: mock-engine/docs/specs/2026-03-20-mock-engine-generalization-design.md