A developer can create a basic Solidity contract by writing source code, compiling it with a compatible compiler, and testing its defined behavior in a controlled environment. Treat the example here as a learning exercise: compilation and basic tests do not establish that a contract is secure or ready for production.

What you need before writing a Solidity contract

A smart contract is code and data deployed through cryptographically signed transactions on a blockchain network. On Ethereum, a smart contract is a reusable program deployed into blockchain state and invoked through transaction requests. These descriptions are general and Ethereum-specific, respectively; other networks may use different execution and storage models. (Claims: claim_nist_code_state_definition, claim_eth_smart_contracts.)

For a small exercise, you need a Solidity source file, a compiler that accepts its declared version range, and a development environment where you can examine the contract’s behavior. This guide does not prescribe a particular tool or provide setup commands. Commands and capabilities depend on the environment you select, so consult its current documentation.

The example below stores one unsigned integer, initializes it at creation, and allows a caller to request a different value. Its narrow purpose is to make basic code structure and test cases concrete. It is not a general-purpose template or evidence of production readiness.

Create solidity contract code with a minimal example

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

contract SimpleValue {
    uint256 public value;

    constructor(uint256 initialValue) {
        value = initialValue;
    }

    function setValue(uint256 newValue) public {
        require(newValue != value, "Value is unchanged");
        value = newValue;
    }
}

The SPDX comment declares a license identifier for the source file. The pragma states a compiler-version constraint; it does not install or choose the compiler. Select a compiler that accepts the declared range, and keep track of the version and settings used so you know what was built.

contract SimpleValue names the contract. The uint256 public value declaration defines an unsigned integer in contract state. The public visibility choice makes the value readable through a compiler-generated getter interface. The constructor accepts an initial integer and stores it when the contract is created.

The setValue function accepts a proposed integer. Its require condition rejects a request that leaves the stored value unchanged; otherwise, the function assigns the new value. This condition is deliberately limited. It does not validate a business rule beyond that single comparison, and it does not restrict who can call the function. A caller with access to the function can request any value that passes the check.

Those choices are acceptable only as a small illustration of syntax and behavior. They are not recommendations for contracts that manage balances, permissions, or assets. For another purpose, define the intended state transitions, valid inputs, and authority model before writing the implementation.

Compile the contract and inspect compiler output

Use a compiler version compatible with the source’s pragma and review the output rather than treating a successful build as a quality verdict. The Solidity compiler can produce outputs such as EVM bytecode, ABI data, metadata, warnings, and other selected information; the exact outputs depend on compiler version and configuration. (Claim: claim_eth_smart_contracts.)

Read compiler errors and warnings. An error prevents the requested compilation, while a warning calls for investigation in context. Do not suppress a message merely to make the build appear clean; determine what it means for this source and its settings. Keep the source, compiler version, and relevant build configuration together when reviewing what was compiled.

An ABI, or application binary interface, is used by applications to encode contract calls and interpret contract results. This guide does not include an application integration, so it does not specify a call implementation. If you later connect an application, the interface information it uses must correspond to the contract and deployment it is meant to interact with.

Compilation establishes only that the compiler produced output from the source under the selected conditions. It does not establish that the code implements the right requirements, that its behavior is safe, or that it is suitable for deployment. Software, compiler, and platform bugs remain possible, and Solidity documentation recommends development practices such as review and testing. (Claim: claim_owasp_verification.)

Test expected behavior and failure cases

Create repeatable tests in the development environment you choose. For this example, make expectations explicit before running each test:

  • Initial state: create the contract with a chosen initial integer and check that reading value returns that integer.
  • Changed state: request a different integer through setValue, then check that the stored value reflects the requested change.
  • Rejected unchanged value: request the current value and check that the operation fails because the require condition is false.
  • Input boundaries: try boundary values that matter to the design you intend to build. State what each case should do; the example itself defines no business-specific minimum or maximum.

If a test fails, inspect the assertion and the operation that produced the result. The failure may indicate a defect in the contract, a mistaken test expectation, or a mismatch between the test setup and the intended behavior. Correct the underlying issue rather than changing a test simply to make it pass.

Tests provide evidence only about the cases and conditions they exercise. Passing these example checks does not prove that the contract is free of vulnerabilities, that all possible inputs behave as intended, or that interactions with other contracts and applications are safe. Expand tests when the requirements become more complex, and seek appropriate independent review before production use.

Review risks before any deployment

Before considering deployment, compare the source and tests with the contract’s actual purpose. Ask who should be authorized to change state, which inputs are valid, and what should happen when a request fails. If the design depends on external information, identify how that information enters the system: Ethereum contracts cannot directly retrieve offchain facts without an oracle mechanism. Deployment and execution also consume gas, but this guide does not estimate fees or assert availability for any network. (Claim: claim_eth_gas_and_oracles.)

Review dependencies and assumptions as well as the functions in the source. A contract may behave differently from expectations if requirements, inputs, or an external component are misunderstood. The review should be specific to the system being built; a simple value-storage example cannot stand in for analysis of a different contract’s risks.

The OWASP Smart Contract Security Verification Standard offers a structured verification framework for designing, building, and testing EVM-based smart contracts and decentralized applications. It is an early-version framework, and project-specific threat modeling and review are still needed. A framework or checklist can organize review, but it is not proof that a contract is safe. (Claim: claim_owasp_verification.)

Treat the code in this guide as an educational example, not as a production template or deployment approval. Whether any particular contract is appropriate to deploy depends on its purpose and implementation, and requires review beyond the small behavior checks shown here. This guide makes no claim about fees, network availability, legal or tax treatment, security guarantees, or recovery if a key or contract fails.

Sources and references