Examples of a simplified and more easily achievable form of automated…

… contract testing.

.github/workflows/contract-tests.yml

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+name: Automated contract tests
+
+on:
+    push:
+        branches: ["main"]
+    pull_request:
+        branches: ["main"]
+
+jobs:
+    contract-tests:
+        runs-on: ubuntu-latest
+
+        strategy:
+            matrix:
+                subproject:
+                    - rest-api
+                    - mocked-mongodb
+                    - mocked-rabbit
+
+        steps:
+            - uses: actions/checkout@v4
+            - uses: actions/setup-node@v3
+              with:
+                  node-version: v20
+
+            - run: npm ci
+              working-directory: ${{ matrix.subproject }}
+            - run: npm test
+              working-directory: ${{ matrix.subproject }}

.gitignore

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+node_modules

README.md

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+# simplified-contract-testing
+
+Examples of a simplified and more easily achievable form of automated contract testing:
+
+- rest-api/         An example of contract testing against an existing REST API.
+- mocked-mongodb/   An example of contract testing a REST API with a mock database.
+- mocked-rabbit/    An example of contract testing a REST API and asynchronous messaging with a mock RabbitMQ.
+
+See README files in subdirectories to learn how to run each example.
+
+You need Node.js installed to run these examples.

mocked-mongodb/README.md

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+#  mocked-mongodb
+
+An example of simplified contract testing against a REST API that is backed by a MongoDB database.
+
+The REST API is based on JSON Placeholder: https://jsonplaceholder.typicode.com/
+
+Built on:
+- Express.js to implement the REST API.
+- MongoDB for the database.
+- Jest for running the tests and matching expectations.
+- Jest is used to mock MongoDB for the automated contract tests.
+- Axios for making the HTTP requests.
+- Jest-json-schema and Ajv for testing the REST API response against the JSON schema in the test spec.
+- Yaml for parsing the test spec.
+
+## Test spec
+
+See the test spec here: [./test/test-spec.yaml](./test/test-spec.yaml).
+
+See the contract testing code here: [./test/contract.test.js](./test/contract.test.js).
+
+## Setup
+
+```bash
+git clone [email protected]:ashleydavis/simplified-contract-testing.git
+cd simplified-contract-testing/mocked-mongodb
+npm install
+```
+
+## Run tests
+
+```bash
+npm test
+```
+
+Note: Testing uses a mocked version of MongoDB.
+
+## Run the REST API
+
+```bash
+npm start
+```
+
+Note: This includes an instant development database.
+

mocked-mongodb/__mocks__/mongodb.js

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+//
+// A mock version of the MongoDB library.
+//
+
+let data = {};
+
+class ObjectId {
+    constructor(value) {
+        this.__value = value;
+    }
+
+    toString() {
+        return this.__value;
+    }
+
+    toJSON() {
+        return this.__value;
+    }
+}
+
+class MongoCollection {
+    constructor(collectionName) {
+        this.collectionName = collectionName;
+    }
+
+    async findOne({ _id }) {
+        const collectionData = data[this.collectionName] || [];
+        return collectionData.find(el => el._id.__value === _id.__value);
+    }
+
+    find() {
+        return {
+            async toArray() {
+                return data[this.collectionName] || [];
+            }
+        }
+    }
+
+    async insertOne() {
+        return {
+            insertedId: new ObjectId("newly-inserted"),
+        };
+    }
+}
+
+class MongoDatabase {
+    collection(collectionName) {
+        return new MongoCollection(collectionName);
+    }
+}
+
+class MongoClient {
+    async connect() {
+    }
+
+    db() {
+        return new MongoDatabase();
+    }
+}
+
+function __setData__(_data) {
+    data = _data;
+}
+
+module.exports = {
+    MongoClient,
+    ObjectId,
+    __setData__,
+};