How to test a Blockchain Application?

2017 was the year of blockchain and cryptocurrencies with media covering these new technology trends daily. Learning blockchain technology might seem fundamentally easy; however, it is different when you understand it deeply. A blockchain can be understood by thinking of it as a block which is a real-time ledger with encrypted and timestamped records linked to the previous blocks.

Almost every industry in the world is adopting blockchain applications because of their potential to build trust and drive transparency to the business ecosystem. Any activities on the blockchain are not under the control of any single or centralised party. Instead, the ledger is controlled by the entire community of members. Everyone within the chain can access the details associated with a block in real-time. Only the owner of the block is allowed to update the information stored in the block using their unique private key.

It is essential to understand that information once written to the blockchain, cannot be updated or removed. Therefore, testing blockchain apps thoroughly is important.

The process of the blockchain app should be tested carefully as flaws found in one block can affect the entire blockchain. Once a block is added to the blockchain, it remains there always. Changes made to any block in the chain can make the linked blocks invalid. As a result, it requires simultaneous fix or update. It is impossible to make such changes later, making it complicated in terms of testing.

Because not all blockchain technologies are open-source, it can be complex to test a blockchain app. However, using some of the right testing techniques can help you test the app efficiently.

Here are some of the factors you should consider before testing the blockchain-based applications:

Testing Environment

Transactions executed in the blockchain update the current state. Miner’s resources are needed to add or update any entry to the blockchain. Miners charge certain fees to verify a transaction and add it to the block. It is the reason why it is expensive to do testing on the live environment.

Using a testnet to run tests will help you cut down on QA costs and get rid of losing money. Testnet coins are different from the actual ones using which testers can test and experiment with the application without worrying about breaking the blockchain.

The team can establish the local testnet or use any publicly available network. For example, the Ropsten network can be used to test Ethereum-based dApps. You would get free coins from a pool of Ethereum faucet to test the applications. Even if you have to use testnet, you will have to interact with miners who validate transactions. Miners are less in numbers on a testnet as compared to the real network. As a result, more time is consumed to validate transactions.

You can set up multiple virtual networks to increase the testing speed and start mining on your own. Unlike the verification of cryptocurrency transactions, it comparatively takes less power.

Transactions are paid

This point is related to the first point. The role of a tester is to ensure the error-free process of transactions processing and adding in the network. Since any transaction in the blockchain needs fees, it makes the testing process specific.

For example, Ethereum transactions carry a specific gas, which is a currency used in the network. Operations requiring more computational resources would need more gas.

It is important to understand the difference between gas price and gas cost.

The gas cost is the amount of work involved in something whereas the gas price is just like the hourly wage paid for the work to be done. The sum of the gas cost and gas price determines the transaction fee.

Now, let’s discuss some of the significant techniques for testing blockchain apps.

With frequent changes to the technology suite, the concept of specialized testing is gaining a lot of traction nowadays. Specialised testing requires specific technology and domain understanding.


Techniques for testing blockchain applications:

Integration Testing

Integration testing is essential from the aspect of requiring different systems to be cohesive. This testing helps test engineers and developers assure the interaction of the code between multiple components and usually between external and internal systems.

Non-functional Testing (Performance)

Performance testing is crucial in blockchain development due to the number of transactions and its size to be tested to check the performance of a block. The team of testers also has to focus on other parameters, including performance bottlenecks, production environment, network latency, transactions sequence at each node, transaction processing speed and responses needed from smart contracts. As the compound testing can have multiple endpoints, consider an end-to-end scenario for performance, which can lead to an automated performance testing to enhance the scalability of the blockchain ecosystem.

API (Application Programming Interface) Testing

API testing tests the interactions of applications that happen back and forth within the network. Testers verify external responses that the application receives and ensures the validity of API request formats. Similar technology exists within the blockchain that enables the same approach to test APIs called smart contracts. Popular API testing tools are SoapUI and Postman.

Non-functional Testing (Security)

The main focus of this testing is to make sure that blockchain apps are tested carefully and to know if they are vulnerable to attacks. If authentication is valid and authorization systems are robust, there is a need to consider other aspects, including integrity, confidentiality, availability and non-denial of services. Testing for security becomes essential in case of identity layer hacking.

A transaction in progress cannot be stopped; therefore, security testing should reveal identity layer hacks. Other challenges related to security testing include private keys, consensus algorithm, wallet signature methods and secure hash.
Once you understand what kind of testing needs to be performed, you need to look at the tools required for testing blockchain-based applications.

Following are some of the testing tools you would require to test the blockchain app:

  • Testnet indexing tool
  • API testing tools (soapUI and Postman)
  • Bug and test tracking tools
  • Encoding and encryption software
  • Database testing tools


Blockchain technology is growing rapidly with each passing day and is opening up opportunities for many industries. Testing should be considered as an integral part of the blockchain development lifecycle to ensure scalability of the blockchain ecosystem. You need to look out for a blockchain development company that provides end-to-end development services, including thorough testing.

If you liked this you might also be interested in other Blockchain resources. See this eBook ‘The Risk and Test in Bitcoin‘ by Declan O’Riordan

About the Author


Akash Takyar is the author of Blockchain Technology and Business book. He is the co-founder of LeewayHertz and is a consultant to fortune 500 companies including Siemens, 3M, Hershey’s and others. He has a Masters Degree in Computer Science. Akash’s experience of building over 100+ apps allows him to rapidly architect and design solutions. His ability to explain complex technologies in simple and practical ways has resulted in him becoming a popular speaker at colleges, universities, and conferences.
Find out more about @akashtakyar