![](https://hackernoon.com/hn-images/1*x26QEuZjUtIYzwk4z3x5bQ.png)

If this is not the first time you hear about [Serverless](https://en.wikipedia.org/wiki/Serverless_computing) and [AWS Lambda](https://aws.amazon.com/lambda/), you might have already seen the Orange Test button in [AWS Lambda](https://aws.amazon.com/lambda/) console which becomes useless when you want to use 3rd party dependencies in your serverless project or if you upload a package of the size larger than a certain size limit.

![](https://hackernoon.com/hn-images/1*u9h62AaNaTAwLdbRs3TduA.png)

AWS Lambda Test Button

![](https://hackernoon.com/hn-images/1*7HY7j9NP_0ogeNaRqSNAIw.png)

Okay. 🙄 Thanks for the information!

Since this **completely breaks the rhythm of the developer**, for [Sigma](https://sigma.slappforge.com) we built a test button, which looks & behaves a little bit different.

![](https://hackernoon.com/hn-images/1*hXJOTedUtNgqJvlQMU9gCg.png)

Sigma’s Test button

This button,

*   Works **Faster**!
*   Doesn’t become useless when you want to add dependencies.
*   Doesn’t become useless when your lambda code is larger.
*   **Tries to avoid cold starts as much as possible for code changes & run-time exceptions.**
*   Allows you to manage Test Events more efficiently.

![](https://hackernoon.com/hn-images/1*KrrdykMPjyR2P9PGNMUPuQ.gif)

Testing Your Code in Sigma

We made all of above possible by utilizing the base concept of the simple trick that I have mentioned in,

[**Writing a self-sufficient AWS Lambda Function**  
_If you have already gone through the SLAppForge’s news articles and blogs, you might already know that bunch of…_hackernoon.com](https://hackernoon.com/writing-a-self-sufficient-aws-lambda-function-da6c0586f48c "https://hackernoon.com/writing-a-self-sufficient-aws-lambda-function-da6c0586f48c")[](https://hackernoon.com/writing-a-self-sufficient-aws-lambda-function-da6c0586f48c)

#### **Deploying the Testing Environment on** [**AWS**](https://aws.amazon.com/)

To achieve all the above-mentioned features, [Sigma](https://sigma.slappforge.com) creates a Test environment on [AWS](https://aws.amazon.com/) when user signup for the first time. This test environment mainly has three major components.

1.  _Dependency Downloader_ Lambda function

![](https://hackernoon.com/hn-images/1*JoEjTvUhZm-IcpHOt4Nsmg.png)

Dependency Downloader

This lambda is responsible for handling all node dependency updates. I’ll explain about the functionality of this function in detail, later in this story.

2\. _Test Runner_ Lambda

![](https://hackernoon.com/hn-images/1*gsJBPldK-PkBQXgt1Xg4qQ.png)

Test Runner Lambda

This lambda will be directly invoked by [Sigma](https://sigma.slappforge.com) IDE to execute the test events on project lambda files.

3\. Code Bucket

![](https://hackernoon.com/hn-images/1*-EifQ44Q1dZW0M_zhwjWgg.png)

Code Bucket

This bucket will be directly utilized by _Dependency Downloader_ Lambda to persist the downloaded dependencies and by [Sigma](https://sigma.slappforge.com) IDE’s _Testing Service_ to persist source files of the project.

#### Handling Dependency Updates

![](https://hackernoon.com/hn-images/1*XCrMCWMUDPpyk9NdhuSlfg.png)

Dependency Update Flow

Unlike in other [serverless](https://en.wikipedia.org/wiki/Serverless_computing) frameworks, adding a dependency is not a painful process in [Sigma](https://sigma.slappforge.com).

![](https://hackernoon.com/hn-images/1*t4Q62dzHT37hBjG8k4WYBA.gif)

Adding a dependency in Sigma

Once you add a dependency to the project, [Sigma](https://sigma.slappforge.com) sends this update in the background to the _Dependency Downloader_ function **which is already deployed in your own AWS account**.

The payload of the _Dependency Downloader_ request takes the following format.

{  
        "project": "${projectName}",  
        "bucketName":"${bucketName}",  
        "dependencies": {  
             "dependency1": "version1",  
             "dependency2": "version2",  
             "dependency3": "version3",  
         }  
}

_Dependency Downloader_ creates a package.json file inside the /tmp/{project\_id} directory of its container using the _dependencies_ property of above event payload.

> With every lambda container(every instance of your function), you get a writable non-persistent disk capacity of 512MB at /tmp directory.

Then following npm command with [prefix flag](https://docs.npmjs.com/misc/config#prefix) is executed to download dependencies to **/tmp/{projectName}/node\_modules** directory

npm --prefix /tmp/projectName install /tmp/projectName

> Since this lambda has nothing else to do concurrently, we use [syncExec](https://nodejs.org/api/child_process.html#child_process_child_process_execsync_command_options) function to spawn all child processes.

Once [syncExec](https://nodejs.org/api/child_process.html#child_process_child_process_execsync_command_options) returns back to the parent process, [archiver](https://www.npmjs.com/package/archiver) is used to generate a zip of freshly created _node\_modules_ directory.

Generated archive (_node\_modules.zip_), is then uploaded to the S3 bucket(_Code Bucket)_ in your [AWS](https://aws.amazon.com/) account with the key {projectName}/node\_modules.zip

> What is a key in S3?

> When you create an object, you specify the key name, which uniquely identifies the object in the bucket. [Read more](https://docs.aws.amazon.com/AmazonS3/latest/dev/UsingMetadata.html).

#### Testing project function Code

![](https://hackernoon.com/hn-images/1*7XrZ8wwsKnHwjhG9t8p_rw.png)

When user click on the ▶️ button, following things happen in order.

1.  **Calling _Invoke Function_ command**

Testing Service of [Sigma](https://sigma.slappforge.com) receives the payload of the _test event_, and the name of the lambda function to invoke.

**2/3. Check source code diff & Update the diff in** [**S3**](https://aws.amazon.com/s3/)

Test Service periodically checks for the source javascript files in the [Sigma](https://sigma.slappforge.com) editor for updates. If an updated file is found, it flags that file as _updated_ and wait for any other subsequent updates. If it doesn’t see any succeeding updates for a while, the content of that particular file is pushed to the [S3](https://aws.amazon.com/s3/)(Code Bucket).

Apart from that, when a test event is invoked, it immediately checks all JS files in the project for updates and pushes them immediately to the [S3](https://aws.amazon.com/s3/) if there are any updates. Due to the periodical update checking that I have mentioned above, number of updated files that will be detected at Test invocation time will be 1 in most of the cases.

Source files will be uploaded to the [S3](https://aws.amazon.com/s3/) with key {projectName}/{fileName}. So this will essentially create a mirror of the project file structure in [S3](https://aws.amazon.com/s3/).

**4\. Invoke Test Runner**

At this step, _Testing Service_ sends Test Event & the name of the Lambda file to be invoked to the _Test Runner_ Lambda. The payload of this invocation takes the following format.

{  
        "project": "${projectName}",  
        "type": "RUN",  
        "lambda": "${path of file relative to the project root}",  
        "bucketName":"${bucketName}",  
        "testEvent": ${event}  
}

**5\. Checking for code updates**

_Test Runner_ function checks for the code updates by checking the ETag of [S3](https://aws.amazon.com/s3/) objects with the prefix {projectName}.

> What is ETag?

> In AWS S3, The entity tag is a hash of the object. The ETag reflects changes only to the contents of an object, not its metadata. The ETag may or may not be an MD5 digest of the object data.

Source files with updated content are then downloaded to the /tmp/{projectName} directory of the lambda container.

> With each lambda instance, you get a **non-persistent space of 512MB at /tmp** location of the lambda container.

At the same time; _Test Runner_ generates(or updates) a collection of {FileName:ETag} tuples and assign it to a global variable declared in the _Test Runner_ function. Since values of global variables are preserved as long as lambda container is running, these values will be available in the next test invocation as well. As a result, number of files that should be downloaded in the upcoming invocations will be minimized.

At the end of this step, _Test Runner_ will have an exact similar copy of project files structure in the /tmp/{projectName} directory of the container.

**6\. Checking for dependency updates**

We already have the dependency bundle for our project at {s3Bucket}/{projectName}/node\_mdoules.zip.

Test Runner applies the same procedure explained above to check whether node\_modules.zip has any updates since the last invocation.

If it finds any mismatch in Etag of node\_modules.zip, _Test Runner_ downloads node\_modules.zip and extracts it to the /tmp/{projectName} of lambda container.

> Unlike in Dependency Downloader function, Step 5 & 6 above happen concurrently, and all S3 GET actions are also executed concurrently.

**7\. Invoking the lambda function**

At the end of above 6 steps, inside the /tmp/{projectName} directory of lambda container, we have a fully functioning node.js project with all required dependencies.

_Test Runner_ Lambda now invokes the intended lambda handler as follows.

It is essential to wrap above handler call with a try/catch block to preserve _Test Runner_ lambda container instance in case of a run-time exception.

Apart from the above-mentioned event, which is of type _RUN_, _Test Runner_ lambda supports another event type, _WARM\_UP_.

{  
       "project": "${projectName}",  
       "type": "WARM\_UP",  
       "bucketName":"${bucketName}",  
       "testEvent": {}  
}

[Sigma](https://sigma.slappforge.com) periodically sends WARM\_UP events to the _Test Runner_ lambda_,_ in order to keep it’s container warmer. Apart from keeping the container warmer, on this event; _Test Runner_ performs 5th and 6th steps above in order to keep /tmp directory up to date with the project.

Even after performing a dependency update, [Sigma](https://sigma.slappforge.com) sends a WARM\_UP request to _Test Runner,_ which makes _RUN_ events faster by keeping the container ready with dependencies.

In most of the test invocations, _Test Runner_ lambda can skip 6th step above due to the hard work done by WARM\_UP requests.

> [Sigma](https://sigma.slappforge.com), at the application level, avoids parallel _Test Runner_ invocations in order to prevent AWS from spawning multiple instances of _Test Runner_. This makes each subsequent test invocations extremely fast. However this is not a guaranteed behavior. If AWS spawn an additional container by accidental concurrent invocation, Sigma will experience a cold start delay just for a single test invocation. But this happens very rarely.

So that’s how we **streamlined** [**Serverless**](https://en.wikipedia.org/wiki/Serverless_computing) **testing** & if you came this far with me, you might be wondering what [Sigma](https://sigma.slappforge.com/) is. So it is the best time to learn about [Sigma](https://sigma.slappforge.com)!!

### What is [Sigma](https://sigma.slappforge.com)?

[Sigma](https://sigma.slappforge.com) was born on 6th of February 2018 in [Sri Lanka](http://www.srilanka.travel/) at [SLAppforge](https://www.slappforge.com/), and it was designed & developed with the vision of making the lives of [Serverless](https://en.wikipedia.org/wiki/Serverless_computing) developers easier.

If you are very new to [Sigma](https://sigma.slappforge.com), let me give you a brief introduction.

[Sigma](https://sigma.slappforge.com) is a tool which makes [Serverless](https://en.wikipedia.org/wiki/Serverless_computing) development smoother.

*   [Sigma](https://sigma.slappforge.com) is not an old-fashioned command line tool.
*   You don’t have to install [Sigma](https://sigma.slappforge.com) on your computer.
*   [Sigma](https://sigma.slappforge.com) runs entirely on your browser(Since chrome is not the only browser in the world, we support all modern web browsers).
*   [Sigma](https://sigma.slappforge.com) gives you the rich experience of a modern integrated development environment (IDE).
*   [Sigma](https://sigma.slappforge.com) updates automatically.

![](https://hackernoon.com/hn-images/1*4sjAHj96yUOB3MYdlwGTYw.png)

You won’t see this in Sigma.

*   [Sigma](https://sigma.slappforge.com) generates code(API calls for other [serverless](https://en.wikipedia.org/wiki/Serverless_computing) services) for you. So developers don’t have to bother about reading API docs.
*   [Sigma](https://sigma.slappforge.com) manages resources (Resources = DynamoDB tables, S3 buckets, etc in AWS) for you.

When it comes to [serverless](https://en.wikipedia.org/wiki/Serverless_computing) development, [Sigma](https://sigma.slappforge.com) gives everything you need to deploy a serverless application from the scratch. Our primary goal is to let you develop your app from a-z within the same browser tab.

So that’s about Sigma and since we have been talking about Sigma’s test framework, let me introduce you the other components of the Test Framework which makes your life easier.

### Components of [Sigma](https://sigma.slappforge.com) Test framework

#### Test Event Manager

![](https://hackernoon.com/hn-images/1*cZqYvfgXVUptDwK7O1uC5Q.png)

Sigma Test Event Manager

Sigma’s Test Event Manager gives you the ability to,

*   Define event payloads for individual functions in your project
*   Duplicate an existing event to create a new test event for the same function or for a different function
*   Invoke functions directly with a desired test event

#### SigmaTrail

![](https://hackernoon.com/hn-images/1*5bfamoqI-MIChX2VZrogEA.png)

Sigma Trail

SigmaTrail displays all your Test invocation results in real time. Apart from the \[TEST\] logs, SigmaTrail also displays \[Prod\] logs for each function which will be generated in production environment when your functions are actually deployed on AWS. Thanks to the SigmaTrail, no more checking [CloudWatch](https://aws.amazon.com/cloudwatch/) for your [serverless](https://en.wikipedia.org/wiki/Serverless_computing) logs.

Hope you enjoyed! Happy coding [Serverless](https://en.wikipedia.org/wiki/Serverless_computing) with [Sigma](https://sigma.slappforge.com).

### Call To Action

*   **Clap.** Appreciate and let others find this article.
*   **Comment.** Share your views on this article.
*   **Follow me.** [Chathura Widanage](https://medium.com/@cwidanage) to receive updates on articles like this.
*   **Keep in touch.** [LinkedIn](https://www.linkedin.com/in/cwidanage/), [Twitter](https://twitter.com/cwidanage)

[**SLAppForge**  
_SLAppForge brings serverless computing and applications into mainstream use for the business success of end users_slappforge.com](https://slappforge.com/ "https://slappforge.com/")[](https://slappforge.com/)

[**Serverless - Hacker Noon**  
_Read writing about Serverless in Hacker Noon. how hackers start their afternoons._hackernoon.com](https://hackernoon.com/tagged/serverless "https://hackernoon.com/tagged/serverless")[](https://hackernoon.com/tagged/serverless)

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