sandpipers-cdk-assertions

sandpipers-cdk-assertions

AssertJ-like fluent assertions for AWS CDK testing

Description

When working with the AWS CDK, it is important to test your stacks to ensure that they are well-formed and that they match your expectations. AWS offers a framework to verify that your stack is well-formed and that it matches your expectations. This framework can be found here.

Here is an example test that a stack contains a specific role:

  template.hasResourceProperties("AWS::IAM::Role", Match.objectEquals(
    Collections.singletonMap("AssumeRolePolicyDocument", Map.of(
        "Version", "2012-10-17",
        "Statement", Collections.singletonList(Map.of(
            "Action", "sts:AssumeRole",
            "Effect", "Allow",
            "Principal", Collections.singletonMap(
                "Service", Collections.singletonMap(
                    "Fn::Join", Arrays.asList(
                            "",
                            Arrays.asList("states.", Match.anyValue(), ".amazonaws.com")
                    )
                )
            )
        ))
    ))
));

Sandpipers' CDK fluent testing library

As you might have noticed, the tests written this way are verbose and present challenges in terms of readability and maintainability. However, don't despair! sandpipers-cdk-assertions allows you to write tests in a more readable and maintainable way. The library is inspired by the AssertJ library and provides a fluent API to test your CDK stacks.

To illustrate, an equivalent representation to the aforementioned example can be found below:

CDKStackAssert.assertThat(template)
  .containsRoleWithManagedPolicyArn(managedPolicyArn)
  .hasAssumeRolePolicyDocument("states.amazonaws.com", null, "Allow", "2012-10-17", "sts:AssumeRole");

Usage

• Import the sandpipers-cdk-bom in your project (if you haven't already done so)

• Add the following dependency to your pom.xml file:

  <dependency>
    <groupId>io.sandpipers</groupId>
    <artifactId>sandpipers-cdk-assertions</artifactId>
    <scope>test</scope>
  </dependency>

• Create a class TemplateSupport in your testing packages. This class will be used to load the template and create the CDKStackAssert object.

  public abstract class TemplateSupport {
  
    public static final String ENV = "test";
    public static final String TEST_CDK_BUCKET = "test-cdk-bucket";
    public static final String QUALIFIER = "test";
    static Template template;
    private static final String STACK_NAME = "example-lambda-function-test-stack";
    
    @TempDir
    private static Path TEMP_DIR;
  
    @BeforeAll
    static void initAll() throws IOException {
      final Path lambdaCodePath = TestLambdaUtils.getTestLambdaCodePath(TEMP_DIR);
  
      final Map<String, String> tags = createTags(ENV, TAG_VALUE_COST_CENTRE);
      final App app = new App();
      final ExampleLambdaStack stack = StackUtils.createStack(app, STACK_NAME, lambdaCodePath.toString(), QUALIFIER, TEST_CDK_BUCKET, ENV);
  
      tags.entrySet().stream()
          .filter(tag -> Objects.nonNull(tag.getValue()))
          .forEach(tag -> Tags.of(app).add(tag.getKey(), tag.getValue()));
  
      template = Template.fromStack(stack);
    }
  
    @AfterAll
    static void cleanup() {
      template = null;
    }
  }

• Extend the TemplateSupport class in your test classes and use the CDKStackAssert object to verify your stack.

  class LambdaTest extends TemplateSupport {
  
    public static final String TEST = "test";
  
    @Test
    void should_have_lambda_function() {
  
      CDKStackAssert.assertThat(template)
          .containsFunction("example-lambda-function")
          .hasHandler("org.springframework.cloud.function.adapter.aws.FunctionInvoker::handleRequest")
          .hasCode("test-cdk-bucket", "(.*).zip")
          .hasRole("examplelambdafunctionrole(.*)")
          .hasDependency("examplelambdafunctionrole(.*)")
          .hasDependency("examplelambdafunctionroleDefaultPolicy(.*)")
          .hasTag("COST_CENTRE", TAG_VALUE_COST_CENTRE)
          .hasTag("ENV", TEST)
          .hasEnvironmentVariable("ENV", TEST)
          .hasEnvironmentVariable("SPRING_PROFILES_ACTIVE", TEST)
          .hasDescription("Lambda example")
          .hasMemorySize(512)
          .hasRuntime("provided.al2")
          .hasTimeout(3);
    }
  }