Automate API Testing using Postman & Newman

AbId KhAn — Mon, 14 Mar 2022 16:12:17 +0000

Introduction:

Postman is one of the most used tools for a developer. Most of the time, we develop APIs and test those individually. But in some scenarios, we have to test APIs in batch if they are dependent on each other. By utilizing the knowledge, we can do our tasks easier as well as minimize the repeating tasks. Through this, our dev testing time can be reduced.

Prerequisites:

Postman
Newman and some of it’s required library

Playground:

In this task, we are using Json placeholder APIs. Postman has the feature to create assertion in the Tests tab. Also, it has the Pre-request script tab to run the script before API request. To minimize the complexity, we are checking only the returned status code of the Tests tab and set variables accordingly.
A snippet to set variables in the POST request body is given below.

{
   "userId": {{userId}},
   "title": "{{title}}",
   "body": "{{body}}"
}

Some most used snippets are already attached beside the Tests tab in Postman to make it easy. A snippet of assertion to check status code is shared below.

pm.test("Successful POST request", function () {
   pm.expect(pm.response.code).to.be.oneOf([201, 202]);
});

Afterward, we are adding the below code to set variables in Postman to use it later. This is like just another Javascript code.

const response = pm.response.json();
if (response && response.id) {
   let pid = response.id;
   pm.environment.set("postId", pid);
}

Now we can use this postId variable in another API request inside the header, body, URL or query parameter.
Now the most interesting part comes, that is, how can we set the variables automatically? We can use Postman runner to do the job. But for this task, we will use the Newman tool. To do so, we will create a CSV file with the header of the variable names (e.g userId, title, body). Now, we can run the below command to request with the CSV file data.

newman run ./jsonplaceholder.postman_collection.json \
   -d ./sample_posts.csv \
   --timeout 300000 \
   --global-var json_placeholder=https://jsonplaceholder.typicode.com \
   --reporters=cli,htmlextra,csv

Also, we can request a specific folder of the collection with the --folder flag. Try to search for the --reporters flag and its usage.
A Github repo automate-api-testing-using-postman is made to review with the document.

Conclusion:

Last but not the least, with Newman, we can get a html-like report view where we can easily get the request/ response information or CSV report if the request volume is high. Finally, we can focus on test cases that are more necessary for developer speed.

Load Balancing Playground with Nginx and Docker

AbId KhAn — Sun, 13 Mar 2022 07:02:10 +0000

Introduction:

Assuming you have already heard the term Load Balancing. If not, then refer you to learn a very basic about the technique from this load balancing wiki. The concept of the task is to make multiple App servers and a Load balancer to balance the traffic. In this writeup, I am sharing my experience to start learning load balancing.

Background:

Different VMs can be created for the app servers and the load balancer in the virtual machine. Also, we have to install multiple services (like nginx) in those VMs that are relatively time consuming. Though the repetitive tasks can be done with some tool like Ansible or the different VMs can be created with Terraform. But to avoid that type of repetitive task or the technique mentioned above, we are using Docker to do the task.

Prerequisites:

Virtual Machine
Docker
Docker Compose

Playground:

Initially, we have started with running multiple docker containers to create a couple of app servers and a load balancer. The commands are given below.

# To create the app servers
docker run --name nginx_1 -d -p 9998:80 nginx
docker run --name nginx_2 -d -p 9997:80 nginx
docker run --name nginx_3 -d -p 9996:80 nginx
# To create a load balancer
docker run --name nginx_balancing -d -p 9999:80 nginx

Afterwards, we have logged in to the different app servers and executed the below command to update the default html file.

# login to app server container
docker exec -it nginx_1 bash
echo '<h1>app 1</h1>' > /usr/share/nginx/html/index.html

# run similar command with different h1 tags 
# to the rest of the servers app 2 and app 3
# try it yourself

Then we have logged in to the load balancer container and updated the default conf with the below configuration according to the guided nginx load balancer configuration. Here the IP (172.17.0.1) is the docker interface IP of the host machine.

# add this to outside the server block
upstream backend {
    server 172.17.0.1:9996;
    server 172.17.0.1:9997;
    server 172.17.0.1:9998;
}

# add this inside the server block
# also inside the "location /" block if exist
location / {
    # load balancer
    proxy_pass http://backend/;
}

Now we are ready to explore the output of the load balancing. Open the browser and browse to the below URL and check the output by reloading the page.

# load balancer URL
http://localhost:9999
# app server 1 URL
http://localhost:9998

The same thing I have done with the docker compose shared in the nginx-load-balancing-docker github repo. In this docker compose file, I’ve just reset the networking technique in the docker compose file and updated the nginx default conf file accordingly. Refer to the trailing snippet to learn about it.

# Nginx default conf for the docker compose file
upstream backend {
   server 10.10.0.2:80;
   server 10.10.0.3:80;
   server 10.10.0.4:80;
}
# the below changes are inside the server block of default conf
location / {
    # load balancer
    proxy_pass http://backend/; 
}

Conclusion:

For me, Docker is a nice tool to play new techniques without installing in the host machine. Therefore I always try to find a docker image to R&D any service that is available in docker hub. And with following this, one can focus on learning the technique instead of setting the environment to decrease time consumption.

Forem: AbId KhAn

Automate API Testing using Postman & Newman

Introduction:

Prerequisites:

Playground:

Conclusion:

Load Balancing Playground with Nginx and Docker

Introduction:

Background:

Prerequisites:

Playground:

Conclusion: