Assertions (XCTAssertEqual, XCTAssertTrue) in Swift

Introduction

Assertions help check if your code works as expected by testing values during development. They stop the program if something is wrong, so you can fix it early.

When you want to check if two values are exactly the same in a test.

When you want to verify a condition is true before continuing.

When writing tests to catch mistakes in your code automatically.

Syntax

Swift

XCTAssertEqual(expression1, expression2, "Optional failure message")
XCTAssertTrue(expression, "Optional failure message")

XCTAssertEqual checks if two values are equal.

XCTAssertTrue checks if a condition is true.

Examples

Checks if numbers or strings are equal.

Swift

XCTAssertEqual(5, 5)
XCTAssertEqual("hello", "hello")

Checks if a condition or boolean variable is true.

Swift

XCTAssertTrue(3 < 5)
XCTAssertTrue(isReady)

Sample Program

This program defines two tests: one checks if 2 + 3 equals 5, and the other checks if 4 is even. If the checks fail, the test will show an error message.

Swift

import XCTest

final class SimpleTests: XCTestCase {
    func testSum() {
        let result = 2 + 3
        XCTAssertEqual(result, 5, "Sum should be 5")
    }

    func testIsEven() {
        let number = 4
        XCTAssertTrue(number % 2 == 0, "Number should be even")
    }
}

SimpleTests.defaultTestSuite.run()

Important Notes

Assertions are mainly used in test code, not in regular app code.

Use clear messages to understand why a test failed.

Summary

Assertions check if your code behaves as expected.

XCTAssertEqual compares two values for equality.

XCTAssertTrue checks if a condition is true.