Gersis Software

How to ensure the quality of smart contracts in dApp? Testing blockchain.

How to ensure the quality of smart contracts in dApp? Testing blockchain.

The world of blockchain and cryptocurrency is primarily associated with decentralization.

This is the reason for the growing popularity of dApp’s (decentralized applications): the lack of centralization eliminates a single point of control, which means it brings convenience, privacy of information, security, reliability, and economy of resources.

Unlike centralized applications, dApps directly connect users and developers without involving an intermediary.

Now the most popular way to release dApp is to install it on the blockchain platform (for example, Ethereum). Live examples of such products are games, DEX (decentralized exchanges), NFT marketplays, gambling, united social networks, DeFi (decentralized finance).

In this article, we will focus on testing smart contracts, as well as discuss how to ensure high quality of decentralized applications.

Advantages of smart contracts

The economy operates through complex contractual agreements that are created and implemented by centralized organizations.

Smart contracts help to gain autonomy and independence from third parties and structures, as well as provide participants in contractual chains with other advantages:

  • reliability;
  • security;
  • accuracy;
  • profitability.

Why we test smart contract?

If errors are found, you cannot change the code of the contract deployed on the network published in the blockchain — in this case, a new contract is created.

Even a small error in the application logic can lead to serious consequences.

A couple of years ago, Parity’s Ethereum multi-subscription wallets were blocked due to vulnerabilities in smart contracts, and the DAO (decentralized autonomous organization) was hacked by an intruder.

Of course, defects could be found at the testing stage before being released to the market.

What is checked in a smart contract?

  • work method of electronic signature;
  • availability of a contract code and fixing of its changes;
  • subject of the contract;
  • tools that are needed for the execution of the contract;
  • conditions of execution, recorded in the code of the contract;
  • events;
  • errors and sending messages;
  • changes in the status of contracts, as well as their balance.

How to test smart contract?

It is necessary to model, take into account and predict all possible conditions that are laid down in the logic of each particular contract:

  • what events should be triggered;
  • what methods should be implemented;
  • how the state and balance of a contract change;
  • to whom and how to transfer funds;
  • what error to cause;
  • check the sender of the message and the correct use of the current time.

For example, when working with Ethereum, it is important to take into account the limitation and spending of the Gas value (the cost of a smart contract that Ethereum has set for its launch) when executing a smart contract.

This is closely related to the security of the agreements, because from a practical point of view, the situation when funds are stuck in the contract forever differs little from the situation when they were stolen.

For the rest, the general principle is similar to testing any other code – creates a set of reference method calls in a predetermined environment, the results of which are prescribed for the expected results.

How to make testing even more effective?

In the case of smart contracts, the most accurate solution would be to automate testing, especially given the large number of validations during contract processing, rapid growth and network transformation, the presence of multiple nodes and their various combinations.

Often, BDD (Behavior-Driven Development) practices are used for defect-free work, which, along with tests, allow you to create documentation and use cases.

What does App have?

Let’s move on to the question of testing decentralized applications.

As you know, any application consists of a back-end and a front-end. The back-end of a decentralized application has its own internal code that runs on the blockchain.

DApp also consists of an intermediate in the form of a browser (for example, Toshi) or extensions for it (like MetaMask). Front-end can be written in any language.

How to test DApp?

Despite the fact that blokcheyn applications remain innovative industry, many of the methods that are used for testing other products also suitable for dApp.

Visually, there is no difference between a dApp and any other application.

Moreover, many users are not even aware that the application in front of them, whose back-end – it blockchain.

We use functional, load testing and security testing that help improve the quality of software products including smart contracts.

In addition to these checks are carried out:

  1. Testing smart contracts.
  2. Transaction Testing. The peculiarity is that test cases include checks of the amount of transactions, conversions, service fields, hash validity, time of the transaction, as well as data about the sender and recipient.
  3. E2E testing. It is used to test the entire functionality of the application from start to finish. It is important that all parts of the integrated dApp worked as it was intended. Typically, the test verifies the real user will interact with the system, and strive to anticipate his / her behavior.
  4. Integration testing. The interaction of modules and systems as a whole, as well as the integration of data that falls from the front-end into the back-end, is checked.

Testing tools:

  • test network – you can deploy your own or use the finished
  • indexer for test network
  • bug and test tracking systems
  • tools for deploying nodes
  • testing tools for API
  • tools for viewing information in the database
  • encoders and encryptors


Getting rid of centralization has become a powerful trend and has greatly simplified work in many industries.

New generation P2P networks, DAO and other dApps, smart contracts, as well as EOS (decentralized OS) are just beginning to gain momentum and determine what the Internet will be like in the future.

Timely testing will help users easily work with blockchain technology, and for companies to take their place in a constantly changing, competitive market and leave room for fresh ideas and innovations.

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