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How to Generate Tests

·457 words·3 mins
Table of Contents

The demo ships with Claude Code slash commands that generate Garland tests. The orders domain — a fully implemented API with no tests — is the blank canvas to practice with.

What you need
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  • Claude Code CLI or IDE extension (VS Code / JetBrains)
  • The demo project open as your working directory

The generation commands are pre-installed in the repo at .claude/commands/. Claude Code picks them up automatically.

The orders domain
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user-service has a complete orders API:

Endpoint Description
POST /api/orders Place an order
GET /api/orders/{id} Get order by ID
PUT /api/orders/{id}/cancel Cancel an order

projection-service consumes order.placed and order.cancelled Kafka events and builds order projection documents in MongoDB. The full stack is running — it just has no tests.

The users test suite is the reference for what good tests look like. The generation commands know the project layout, factories, mappers, clients, and rules — they produce output that matches the existing style.

Generation commands
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/gen-endpoint-test
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Generates a TestNG endpoint test class. One class per endpoint, covering the happy path and all validation and error cases.

/gen-endpoint-test PlaceOrderApiTest — full suite
/gen-endpoint-test CancelOrderApiTest — happy path and 404
/gen-endpoint-test GetOrderApiTest — happy path and not found

/gen-flow-test
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Generates a flow test class covering state transitions across a sequence of endpoint calls within one service.

/gen-flow-test OrderFlowTest — place then cancel lifecycle
/gen-flow-test OrderFlowTest — full CRUD sequence

/gen-component-test
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Generates component tests that verify a single service boundary end-to-end.

/gen-component-test OrderApiToKafkaTest — place order publishes event and persists to Postgres
/gen-component-test KafkaToOrderProjectionTest — order event projected to MongoDB

/gen-e2e-test
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Generates an end-to-end test class that walks the full chain: HTTP → Postgres → Kafka → MongoDB.

/gen-e2e-test OrderEndToEndTest — place and cancel flows

How to run
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Open the demo project in Claude Code and type a command with a description:

/gen-endpoint-test PlaceOrderApiTest — full suite

Claude Code reads the existing users test suite as a reference, applies the project-specific rules baked into the command, and generates a complete test class in the correct package with the correct imports, factories, and cleanup.

Run the generated tests immediately:

mvn test -pl tests -Dtest=PlaceOrderApiTest

What the commands know
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Each command comes pre-loaded with the project’s conventions:

  • Package structure and class naming
  • Which clients are available (httpClient, postgresClient, kafkaClient, orderKafkaClient, mongoClient)
  • All factory methods (TestOrderRequests, TestOrders, TestOrderItems, TestOrderEvents)
  • Mapper bridge methods for the orders domain
  • Cleanup rules (trackOrder() after every makeCall(201, OrderDto.class))
  • Error DTO shapes (ValidationErrorDto for 400, ErrorDto for everything else)
  • When to use Verify.allOf vs sequential .then() calls
  • Cross-domain FK handling (orders reference a user — create the user first in happy-path tests)

The generated output requires no manual editing for structure or imports — it compiles and runs as-is.