---
title: "Smart Contracts without surprises: common mistakes in Solidity and how to avoid them"
url: "https://www.unknowngravity.com/en/articulos/smart-contracts-soliditys-errores-comunes-y-como-evitarlos"
site: Unknown Gravity
published: "2025-06-06T15:07:09+00:00"
modified: "2026-07-15T10:51:32+00:00"
language: en-US
description: Smart contracts have revolutionized the way digital agreements are created. However, with its power comes great responsibility.
section: "Home > Blockchain > Smart Contracts without surprises: common mistakes in Solidity and how to avoid them"
---

# Smart Contracts without surprises: common mistakes in Solidity and how to avoid them

> The usual pitfalls when writing Solidity contracts are well documented: reentrancy from transferring funds before updating state, poorly defined access control on critical functions, reliance on manipulable external data, and assuming arithmetic will not overflow. Almost all of them are avoided with audited libraries and external review.

Smart contracts have revolutionized the way digital agreements are created. However, with its power comes great responsibility.

In blockchain, errors are not corrected with a simple patch: they are public, permanent and can have a real financial impact.

In this article, we analyze the most common errors when programming smart contracts in Solidity, bad practices to avoid, and how to establish a solid test environment that minimizes risks.

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## Common errors in smart contracts developed in Solidity

### 1. Reentrancy: one of the most exploited flaws

A reentry attack allows an external function to call the contract again before its execution ends, altering the logical flow.

**How to avoid it**:

- Follow the pattern `checks-effects-interactions`.
- Use the modifier `NonReentrant` from the OpenZeppelin library.
- Minimize external calls when possible.

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### 2. Integer overflows and underflows

Before Solidity 0.8, integers could overflow silently. Although current versions prevent this by default, it's still important to be aware of the risk.

**How to avoid it**:

- Use compilers equal to or greater than `^0.8.0`.
- Don't rely on arithmetic logic without explicit validations.

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### 3. Incorrect use of `tx.origin`

To use `tx.origin` to authenticate the end user is a common security mistake. This value changes if the contract is called by another contract.

**How to avoid it**:

- Utilize `msg.sender` to verify the identity of the issuer.
- Apply clear roles and authorization mechanisms.

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### 4. Public functions without access control

Exposing critical functions without restrictions has led to exploits in multiple contracts. From self-destruct functions to unauthorized transfers.

**How to avoid it**:

- Add modifiers such as `OnlyOwner` Do you use it `Access Control`.
- Audit all public and external functions.

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### 5. Loops and costly operations without gas control

A contract can become unusable if it consumes more gas than allowed in a single transaction.

**How to avoid it**:

- Avoid loops that grow dynamically with arrays.
- Divide complex operations into paginated functions or multiple transactions.

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## Best Practices for the Secure Development of Smart Contracts

### Modular design and safe reuse

Avoid monolithic contracts. It divides the code into auditable modules and reuses libraries such as those in OpenZeppelin.

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### Error Management and Recovery

It implements emergency mechanisms such as `Pausable` and consider upgrade (proxy) systems if your architecture allows it.

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### Third-party validation

Never integrate contracts or external libraries without reviewing their code, audit history and reputation.

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## Professional testing strategies in Web3

### Unit Tests

Use environments such as Hardhat, Foundry or Truffle to write detailed tests for each function. Make sure to cover:

- Happy Paths
- Boundary conditions (edge cases)
- Expected errors (reverts)

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### Fuzz testing

Fuzzing allows you to detect errors with random or unexpected data. It is useful for finding inconsistencies in mathematical functions and complex logic.

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### Static analysis

Tools such as **Slither**, **MythX** or **Securify** allow us to identify common vulnerabilities before deployment.

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### Network simulations

Perform tests on realistic testnets or mainnet forks to validate interaction with existing protocols, measure gas consumption and observe behavior under real conditions.

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## Conclusion

In blockchain, there is no room for improvisation. Smart contracts require a meticulous approach, from writing the code to its testing and deployment.

Avoiding common mistakes and following good development practices can make the difference between a functional product and a public disaster.

At Unknown Gravity, we help Web3 companies and projects to design, audit and deploy smart contracts with guarantees.

If you need specialized support in blockchain development, we can accompany you in every phase.