Typescript Cdk Testing

tests/iac/
├── bin/
│   └── main.test.ts                  CDK app entry point test
├── lib/
│   ├── stacks/
│   │   ├── cloudfrontUrlRewrite.test.ts
│   │   ├── staticWebsiteStack.test.ts
│   │   └── __snapshots__/
│   └── utils/
│       └── cloudFormationUtils.test.ts
├── package.json
├── tsconfig.json
└── vitest.d.ts

import { App } from "aws-cdk-lib";
import { Template } from "aws-cdk-lib/assertions";

describe("StaticWebsiteStack", () => {
    it("Should_MatchSnapshot_When_StackIsSynthesized", () => {
        // Arrange
        const app = new App();
        const stack = new StaticWebsiteStack(app, "TestStack", config);

        // Act
        const template = Template.fromStack(stack);

        // Assert
        expect(template).toMatchSnapshot("staticWebsiteStackTest");
    });
});

function normalizeTemplate(template: Template): object {
    const json = template.toJSON();
    for (const resource of Object.values(json.Resources ?? {})) {
        if (resource.Properties?.Code?.S3Key) {
            resource.Properties.Code.S3Key = "NORMALIZED";
        }
        if (resource.Properties?.SourceObjectKeys) {
            resource.Properties.SourceObjectKeys = ["NORMALIZED"];
        }
    }
    return json;
}

pnpm test -- -u

import { Template, Match } from "aws-cdk-lib/assertions";

describe("LambdaStack", () => {
    it("Should_HaveCorrectTimeout_When_ApiLambdaIsCreated", () => {
        // Arrange
        const app = new App();
        const stack = new LambdaStack(app, "TestStack", config);
        const template = Template.fromStack(stack);

        // Act & Assert
        template.hasResourceProperties("AWS::Lambda::Function", {
            Timeout: 30,
            MemorySize: 1024,
            Runtime: "provided.al2023",
        });
    });

    it("Should_HaveDeadLetterQueue_When_SqsIsCreated", () => {
        // Arrange
        const app = new App();
        const stack = new SqsStack(app, "TestStack", config);
        const template = Template.fromStack(stack);

        // Act & Assert
        template.hasResourceProperties("AWS::SQS::Queue", {
            RedrivePolicy: Match.objectLike({
                maxReceiveCount: 3,
            }),
        });
    });
});

it("Should_MatchSnapshot_When_StackIsSynthesized", ...)
it("Should_HaveCorrectTimeout_When_ApiLambdaIsCreated", ...)
it("Should_CreateDeadLetterQueue_When_SqsHasMaxReceiveCount", ...)
it("Should_RestrictPublicAccess_When_S3BucketIsCreated", ...)

const testConfig: BackendStackConfig = {
    lambdas: [{ name: "TestLambda", timeoutSeconds: 30, memorySizeMbs: 1024 }],
    sqs: [{ name: "test-queue", maxReceiveCount: 3, deadLetter: true }],
    s3: [{ bucketNameSuffix: "test-bucket" }],
    fargates: [{ name: "TestService", cpu: 256, memoryLimitMiB: 512 }],
};

# Run all CDK tests
cd tests/iac && pnpm test

# Update snapshots (after intentional changes only)
cd tests/iac && pnpm test -- -u

# Run specific test file
cd tests/iac && pnpm test -- lib/stacks/staticWebsiteStack.test.ts

# Filter by test name
cd tests/iac && pnpm test -- -t "Should_MatchSnapshot"