Testing by Example

Testing Smart Contracts in Q-Remix

Q-Remix supports writing and running Solidity unit tests directly within your workspace using a Remix-compatible test runner. This guide walks you through the basics of writing smart contract tests, setting up your test environment, and using advanced features like multiple accounts and error handling.

File Structure

All test files should end with _test.sol and reside in the same directory or a dedicated tests/ folder. For example:

contracts/ │ ├── MyContract.sol ├── MyContract_test.sol

Writing Your First Test

Contract: SimpleStorage.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract SimpleStorage {
    uint public storedData = 42;

    function set(uint x) public {
        storedData = x;
    }

    function get() public view returns (uint) {
        return storedData;
    }
}

Test: SimpleStorage_test.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "remix_tests.sol"; // Remix test framework
import "./SimpleStorage.sol";

contract SimpleStorageTest {
    SimpleStorage store;

    function beforeEach() public {
        store = new SimpleStorage();
    }

    function checkInitialValue() public {
        Assert.equal(store.get(), 42, "Initial value should be 42");
    }

    function checkUpdatedValue() public {
        store.set(100);
        Assert.equal(store.get(), 100, "Value should update to 100");
    }
}

Handling Reverts and Errors

Use try-catch blocks to assert that a transaction should revert with a specific reason.

function testShouldRevert() public {
    try someContract.doRestrictedAction() {
        Assert.ok(false, "Expected revert but call succeeded");
    } catch Error(string memory reason) {
        Assert.equal(reason, "Action not allowed", "Unexpected revert reason");
    }
}

Common Assertions

Function	Description
Assert.equal(a, b, msg)	Check if a == b
Assert.notEqual(a, b, msg)	Check if a != b
Assert.ok(condition, msg)	Check if condition == true
Assert.isFalse(condition, msg)	Check if condition == false

Tips

• Always use beforeEach() or beforeAll() to set up fresh instances.

• Use #sender: annotations for testing with different accounts.

• Prefer testing both success and failure paths for better coverage.

• Keep test names descriptive: shouldFailIf, shouldRevertWhen, returnsExpectedResult, etc.

Advanced Topics

• Testing imported contracts from GitHub (e.g., OpenZeppelin)

• Mocking and faking behavior

• Custom event assertions (via logs)

📎 For event testing and full debugging, check the Q-Remix logs and console panel.