test(jest): prepare unit tests

Author: floydspace

package.json

@@ -38,6 +38,7 @@
     "typescript"
   ],
   "devDependencies": {
+    "@aws-cdk/assert": "^1.70.0",
     "@aws-cdk/aws-lambda": "^1.70.0",
     "@aws-cdk/core": "^1.70.0",
     "@commitlint/cli": "^11.0.0",

src/index.ts

@@ -1,5 +1,42 @@
 import * as lambda from '@aws-cdk/aws-lambda';
+import * as cdk from '@aws-cdk/core';
+
+import { nodeMajorVersion } from './utils';
+
+export interface NodejsFunctionProps extends lambda.FunctionOptions {
+  /**
+   * The name of the exported handler in the entry file.
+   *
+   * @default "handler"
+   */
+  readonly handler?: string;
+  /**
+   * The runtime environment. Only runtimes of the Node.js family are
+   * supported.
+   *
+   * @default - `NODEJS_12_X` if `process.versions.node` >= '12.0.0',
+   * `NODEJS_10_X` otherwise.
+   */
+  readonly runtime?: lambda.Runtime;
+}
 
 export class NodejsFunction extends lambda.Function {
+  constructor(scope: cdk.Construct, id: string, props: NodejsFunctionProps = {}) {
+    if (props.runtime && props.runtime.family !== lambda.RuntimeFamily.NODEJS) {
+      throw new Error('Only `NODEJS` runtimes are supported.');
+    }
+
+    const handler = props.handler ?? 'handler';
+    const defaultRunTime = nodeMajorVersion() >= 12
+      ? lambda.Runtime.NODEJS_12_X
+      : lambda.Runtime.NODEJS_10_X;
+    const runtime = props.runtime ?? defaultRunTime;
 
+    super(scope, id, {
+      ...props,
+      runtime,
+      code: lambda.Code.fromInline('TODO'),
+      handler: `index.${handler}`,
+    });
+  }
 }

src/utils.ts

@@ -0,0 +1,6 @@
+/**
+ * Returns the major version of node installation
+ */
+export function nodeMajorVersion(): number {
+  return parseInt(process.versions.node.split('.')[0], 10);
+}

tests/index.test.ts

@@ -0,0 +1,14 @@
+import '@aws-cdk/assert/jest';
+import { Stack } from '@aws-cdk/core';
+import { NodejsFunction } from '../src';
+
+describe('NodejsFunction tests', () => {
+  it('Should not class constructor be thrown', async () => {
+    const stack = new Stack();
+    const factory = () => new NodejsFunction(stack, 'lambda-function', {});
+    expect(factory).not.toThrow();
+    expect(stack).toHaveResource('AWS::Lambda::Function', {
+      Handler: 'index.handler',
+    });
+  });
+});