test/UnitTestProject1/UnitTest1.cs

using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;
using WpfApp1;

namespace UnitTestProject1
{
    [TestClass]
    public class UnitTest1
    {
        private MainWindow mainWindow;

        [TestInitialize]
        public void Setup()
        {
            mainWindow = new MainWindow();
        }


        [TestMethod]
        public void TestInputIsValid_WithValidNumber_ReturnsTrue()
        {
            string validInput = "1234";

            bool result = mainWindow.IsInputValid(validInput);

            Assert.IsTrue(result);
        }

        //проверка на пустое значение
        [TestMethod]
        public void TestInputIsValid_WithEmptyInput_ReturnsFalse()
        {
            string emptyInput = "";

            bool result = mainWindow.IsInputValid(emptyInput);

            Assert.IsFalse(result);
        }

        //проверка на ввод букв
        [TestMethod]
        public void TestInputIsValid_WithNonNumericInput_ReturnsFalse()
        {
            string nonNumericInput = "abc";

            bool result = mainWindow.IsInputValid(nonNumericInput);

            Assert.IsFalse(result);
        }
    }
}