Assertion Tests

Fine-Grained Assertion Tests #

Create a test for the DynamoDB table #

This section assumes that you have created the hit counter construct

Our HitCounter construct creates a simple DynamoDB table. Lets create a test that validates that the table is getting created.

Prerequisites #

Visual Studio Required for this testing workshop, download here

Getting started testing your CDK code #

Open src/CdkWorkshop/CdkWorkshop.slnin Visual Studio
In Solution Explorer, add Project Tests > MSTest Project named CdkWorkshopTests
From terminal, from directory CdkWorkshop.sln resides in, run dotnet test to see single placeholder test pass
Rename boilerplate UnitTest1.cs file to HitCounterTest.cs
In Solution Explorer, add reference to CdkWorkshop project from CdkWorkshopTests
In Solution Explorer, add Amazon.CDK, Amazon.CDK.lib, and Amazon.CDK.Assertions NuGet packages to the CdkWorkshopTests project

Create test suite and add test for creation of DynamoDB Table #

Update the contents of the HitCounterTest.cs to add test ensure DynamoDB Table was created:

namespace CdkWorkshopTests;

using Amazon.CDK;
using Amazon.CDK.Assertions;
using CdkWorkshop;

using ObjectDict = Dictionary<string, object>;

[TestClass]
public class HitCounterTest
{
    private Template template;

    [TestInitialize()]
    public void Startup()
    {
        //Create directory that is used when creating lambda in stack 
        Directory.CreateDirectory("lambda");

        var app = new App();
        var stack = new CdkWorkshopStack(app, "test-stack");
        template = Template.FromStack(stack);
    }

    [TestCleanup()]
    public void Cleanup()
    {
        Directory.Delete("lambda");
    }


    [TestMethod]
    public void DynamoDBTableCreated()
    {
        template.ResourceCountIs("AWS::DynamoDB::Table", 1);
    }
}

Run the test and ensure test passes:

$ dotnet test

You should see output like this:

$ dotnet test

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.

Passed!  - Failed:     0, Passed:     1, Skipped:     0, Total:     1, Duration: 15 ms - CdkWorkshopTests.dll (net7.0)

Add test to ensure HitCounter Lambda is created #

[TestMethod]
public void StackCreatesHitCounterHandler()
{
    template.HasResourceProperties("AWS::Lambda::Function", new ObjectDict {
        { "Handler", "hitcounter.handler" },
        { "Environment", Match.AnyValue() }
    });
}

Notice the usage of Match.AnyValue:

template.HasResourceProperties("AWS::Lambda::Function", new ObjectDict {
    { "Handler", "hitcounter.handler" },
    { "Environment", Match.AnyValue() }
});

This allows us to ignore properties that do not apply or we do not understand how to define.

Add a test to ensure the lambda is created with correct environment variables #

[TestMethod]
public void HitCounterLambdaEnvironmentVariablesCorrect()
{
    var functionCapture = new Capture();
    var tableCapture = new Capture();

    template.HasResourceProperties("AWS::Lambda::Function", new ObjectDict {
        { "Handler", "hitcounter.handler" },
        {
            "Environment", new ObjectDict {
                {
                    "Variables", new ObjectDict {
                        { "DOWNSTREAM_FUNCTION_NAME", functionCapture },
                        { "HITS_TABLE_NAME", tableCapture },
                    }
                }
            }
        }
    });

    Assert.IsTrue(functionCapture.AsObject()["Ref"].ToString().StartsWith("HelloHandler"));
    Assert.IsTrue(tableCapture.AsObject()["Ref"].ToString().StartsWith("HelloHitCounterHits"));
}

Notice the usage of argument captors:

template.HasResourceProperties("AWS::Lambda::Function", new ObjectDict {
    { "Handler", "hitcounter.handler" },
    {
        "Environment", new ObjectDict {
            {
                "Variables", new ObjectDict {
                    { "DOWNSTREAM_FUNCTION_NAME", functionCapture },
                    { "HITS_TABLE_NAME", tableCapture },
                }
            }
        }
    }
});

Assert.IsTrue(functionCapture.AsObject()["Ref"].ToString().StartsWith("HelloHandler"));
Assert.IsTrue(tableCapture.AsObject()["Ref"].ToString().StartsWith("HelloHitCounterHits"));

This allows us to capture parameters passed to the CDK method that we used to define our table

Using these captors, we can make an assertion on the Ref property in the generated CloudFormation template for the DOWNSTREAM_FUNCTION_NAME and HITS_TABLE_NAME environment variables

The StartsWith method is used to reduce risk of the tests not functioning as expected due to randomly generated characters that are appended to the resource names during generation of CloudFormation.

Add test to ensure DynamoDB table created with correct key #

[TestMethod]
public void DynamoDBTableCreatedWithCorrectKey()
{
    var keySchemaCapture = new Capture();
    
    template.HasResourceProperties("AWS::DynamoDB::Table", new ObjectDict {
        { "KeySchema", keySchemaCapture },
        { "AttributeDefinitions", Match.AnyValue() },
        { "ProvisionedThroughput", Match.AnyValue() },
    });

    var expectedKeyAttributes = new[] { "path" };
    var actualKeyAttributes = keySchemaCapture.AsArray().Select(x =>
        (x as ObjectDict)["AttributeName"].ToString()).ToArray();

    CollectionAssert.AreEqual(expectedKeyAttributes, actualKeyAttributes);
}

Wrapping up #

At this point you should have 4 passing tests:

$ dotnet test                                                                                    

Test run for /Users/kev/src/aws-cdk-intro-workshop/code/csharp/test-workshop/src/CdkWorkshopTests/bin/Debug/net7.0/CdkWorkshopTests.dll (.NETCoreApp,Version=v7.0)
Microsoft (R) Test Execution Command Line Tool Version 17.5.0 (x64)
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.

Passed!  - Failed:     0, Passed:     4, Skipped:     0, Total:     4, Duration: 7 s - CdkWorkshopTests.dll (net7.0)

Congrats, nice work!

This portion of the workshop has provided only a small overview of testing csharp CDK solutions. For more information, view the C# samples in the user guide.

Page Todo #

Figure out commands to do things instead of Visual Studio solution explorer things, got idea from here
Manage nuget packages via CLI, e.g.: dotnet add package Amazon.CDK.Assertions
Remove need for Visual Studio