Banking Kata - Java

Overview

This project illustrates TDD & Clean Architecture implementation in Java, showing the Use Case Driven Development Approach.

This demo was created for the purposes of meetup series on TDD & Clean Architecture. See the YouTube Meetups. Please note that this project is purely for demo purposes only.

Business Requirements

We implement a Banking system with the following use cases:

Open account
Withdraw funds
Deposit funds
View account

We also have authentication with Keycloak - a realm with client_id and with client_credentials flow enabled.

Architecture

The overall architecture is split into:

Application Core (core) layer contains the business logic.
Adapter (adapter) layer contains the infrastructural concerns.

The Application Core(core) is composed of:

Ports (ports), representing an interface to the Application Core, isolating it from infrastructural concerns. There are both Driver (driver) ports, representing use cases; and Driven (driven) ports, representing gateways.
Internals (internal), representing the internal implementation of the Application Core, more specifically, the implementation of the Driver (driver) ports. This implementation can be anything. Here we illustrate the implementation with Clean Architecture (cleanarch) approach and the CRUD (crud) approach, but other approaches are possible too. The use case tests are independent of the implementation approach; the internal implementation is thus swappable.

The Adapter (adapter) layer is composed of driver adapters and driven adapters.

Driver adapters: REST API Adapter (adapter-restapi-*)
Driven adapters: Persistence Adapters (adapter-persistence-*), Random Number Generation Adapters (adapter-generation-*), Time Adapters (adapter-time-*), Third Party Integration Adapters (adapter-thirdparty-*), and Messaging Adapters (adapter-messaging-*).

The application can be executed via startup.

Tests

Core Layer: Unit Tests targeting the Driver Ports.
Adapter Layer: Integration Tests targeting the Driven Ports. In cases of integrating with third-party systems or microservices, we use Contract Testing.

As can be seen below, you can separately run these fast-running and slow-running tests.

Prerequisites

OpenJDK 17
Docker

Running Unit Tests

Run unit tests for core:

./gradlew coreTest

Running Integration Tests

Apply the environment variables (Windows):

. .\env\env.ps1

Apply the environment variables (for Linux/Mac):

source ./env/env.sh

For Mac only, you need to build a custom Keycloak image to enable Keycloak to work on Mac M1. This is due to a reported Mac-specific issue docker/for-mac#5310. For any other OS, please skip this step, because this issue is Mac-specific:

./src/main/resources/keycloak/build-keycloak-image-m1.zsh 16.0.0

Run docker:

docker-compose up -d

To run all the adapter integration tests:

./gradlew adapterTest

Running System Tests

To run the whole system:

./gradlew systemTest

Running all Tests

In the above instructions, we ran the tests separately. You can run them all:

./gradlew test

Running Code Coverage

Run code coverage (executes Jacoco):

./gradlew codeCoverage

Running Mutation Testing

Run mutation testing (executes pitest):

./gradlew mutationTest

Viewing Reports

See the build\reports directory for the generated reports for test results, code coverage and mutation testing.

Reports:

build\reports\tests
build\reports\jacoco
build\reports\pitest

Running Spring Boot

To manually run the app.

./gradlew runApp

Then CTRL+C to terminate the app.

Optional Notes

The following are for additional reading, you do not need to execute these, but you can if you wish.

Environment variables are located inside the env folder. You can optionally choose to edit them.

You can choose to run the tests via IntelliJ UI.

In the case of integration tests (for adapters) you'd have to specify environment variables before you run the tests. To do that, you can copy the text from the file env/env.intellij.ui into the Environment variables section into Tests in 'banking-kata.adapters' configuration.

To run Docker with the environment file:

docker-compose --env-file=env/.env.local up -d

You can run the integration tests individually, e.g. if you modified a module (in this way you avoid waiting for all of them to finish):

./gradlew adapter-persistence-jpa:test

For code coverage, the underlying call is:

./gradlew jacocoTestReport

For mutation testing, the underlying call is:

./gradlew pitest

Issues

If you experience Integration Tests failing, please see the following known issue valentinajemuovic#64.

If you experience any other issues, please create a ticket https://github.com/valentinacupac/banking-kata-java/issues/new

Contributors

Our contributors are:

Contributing

If you'd like to contribute, see instructions here https://github.com/valentinacupac/banking-kata-java/blob/main/CONTRIBUTING.md

murodin/banking-kata-java