A demo/training E2E test project for a Master Data Management (MDM) service. It validates the async flow Kafka → processing → MongoDB using a child entity (detail) linked to a parent entity. Suitable as a reference architecture for E2E tests in enterprise systems with message queues and a document database.

• Consuming messages from Kafka (IN topic)
• Data updates and consistency in MongoDB (Instance / Master)
• Business rules: updating an existing master vs creating a new one when the business key changes
• Instance ↔ Master linkage and belonging to the parent entity

Tests focus on business behavior (that changes occur and rules are correct), not on exact payload matching.

• JDK 17+
• Access to Kafka (bootstrap servers) and MongoDB
• MDM service that consumes from the IN topic and writes to the DB (and optionally to the OUT topic)

1. Copy the example config:

   cp src/test/resources/application.properties.example src/test/resources/application.properties

2. Edit application.properties: set your kafka.bootstrap.servers, mongo.uri, mongo.database, topic names and, if needed, test.detail.parent_master_guid / test.detail.parent_source_id (E2E requires existing test data).
3. Do not commit application.properties with real hosts and passwords — only application.properties.example should be in the repo. If the file was already tracked:
   git rm --cached src/test/resources/application.properties

mvn test

Single test:

mvn test -Dtest=DetailUpdateE2ETest

Structure is organized by entities, not by technical layers — easy to scale to other domains.

example.mdm
├── common
│   └── assertions          # Shared assertions (instance, master, versioning)
├── config
│   └── TestConfig          # Loads application.properties
├── entities
│   └── detail              # Child entity (detail)
│       ├── context         # ScenarioContext (input data + before/after snapshots)
│       ├── payload         # Kafka payload building
│       ├── dao             # MongoDB collection access
│       ├── steps           # Flow: snapshot → Kafka IN → wait → snapshot
│       ├── assertions      # Domain assertions + Kafka OUT
│       └── tests           # E2E tests
└── infrastructure
    ├── kafka               # Producer, Consumer, event awaiting
    └── mongo               # Client and versioning strategy

• Parent entity — identifier parentMasterGuid to which child records (detail) are linked.
• Detail Master — one document of the child entity; business key is the number field.
• Detail Instance — versions of one master; relation instance.masterGuid = master._id.

Business rule: master is updated only when the business key is unchanged; a new key creates a new master.

1. Snapshot instance + master before (if any).
2. Send message to Kafka (IN topic).
3. Wait for instance to appear/update in MongoDB (Awaitility).
4. Snapshot instance + master after.
5. Assert: structure, parent linkage, field deltas, versioning rule (same master vs new master).

Use the code as a reference or base for your own projects. Configuration and environment are your own.