C#窗体按钮功能单元测试示例请求：基于NUnit/XUnit实现Save与Delete按钮测试

Hey there, I get where you're coming from—testing WinForms button click events can feel tricky because most tutorials focus on pure business logic, not UI-coupled code. The key here is to decouple your business logic from the UI first, so you can test the core functionality with NUnit/xUnit without needing to run the entire form. Let me walk you through how to do this with examples:

1. Refactor Your Code to Separate Logic from UI #

Right now, your database operations and validation logic are tightly tied to UI controls (like PrNameTb or CatCb), which makes them hard to test. Let's move that logic into a separate service class:

Step 1.1: Create a Product Service Class #

This class will handle all database interactions and validation, using plain parameters instead of UI controls:

using System.Data.SqlClient;

public class ProductService
{
    private readonly string _connectionString;

    // Inject the connection string for flexibility (test vs production)
    public ProductService(string connectionString)
    {
        _connectionString = connectionString;
    }

    public string AddProduct(string productName, string category, string quantity, string price)
    {
        // Input validation (same as your original code)
        if (string.IsNullOrEmpty(productName) || string.IsNullOrEmpty(category) 
            || string.IsNullOrEmpty(quantity) || string.IsNullOrEmpty(price))
        {
            return "Missing Information";
        }

        try
        {
            // Use 'using' to automatically close connections
            using (var con = new SqlConnection(_connectionString))
            {
                con.Open();
                var cmd = new SqlCommand(
                    "INSERT INTO ProductTbl (PrName, PrCat, PrQty, PrPrice) VALUES (@PN, @PC, @PQ, @PP)", 
                    con);
                cmd.Parameters.AddWithValue("@PN", productName);
                cmd.Parameters.AddWithValue("@PC", category);
                cmd.Parameters.AddWithValue("@PQ", quantity);
                cmd.Parameters.AddWithValue("@PP", price);
                cmd.ExecuteNonQuery();
                return "Product Added";
            }
        }
        catch (Exception ex)
        {
            return ex.Message;
        }
    }

    public string DeleteProduct(int productId)
    {
        if (productId == 0)
        {
            return "Select an Product";
        }

        try
        {
            using (var con = new SqlConnection(_connectionString))
            {
                con.Open();
                var cmd = new SqlCommand(
                    "DELETE FROM ProductTbl WHERE PrId = @PKey", 
                    con);
                cmd.Parameters.AddWithValue("@PKey", productId);
                cmd.ExecuteNonQuery();
                return "Product Deleted";
            }
        }
        catch (Exception ex)
        {
            return ex.Message;
        }
    }
}

Step 1.2: Simplify Your Button Click Events #

Now update your form's code to use the service instead of embedding logic directly:

public partial class YourProductForm : Form
{
    private readonly ProductService _productService;
    public int Key { get; set; } // Keep your existing Key property

    // Initialize the service in the form constructor
    public YourProductForm(string connectionString)
    {
        InitializeComponent();
        _productService = new ProductService(connectionString);
    }

    private void Savebtn_Click(object sender, EventArgs e)
    {
        string category = CatCb.SelectedItem?.ToString();
        string result = _productService.AddProduct(PrNameTb.Text, category, QtyTb.Text, PriceTb.Text);
        
        MessageBox.Show(result);
        if (result == "Product Added")
        {
            DisplayProducts();
            Clear();
        }
    }

    private void DeleteBtn_Click(object sender, EventArgs e)
    {
        string result = _productService.DeleteProduct(Key);
        
        MessageBox.Show(result);
        if (result == "Product Deleted")
        {
            DisplayProducts();
            Clear();
        }
    }

    // Keep your existing DisplayProducts() and Clear() methods
    private void DisplayProducts() { /* ... */ }
    private void Clear() { /* ... */ }
}

2. Write Unit Tests for the Business Logic #

Now you can easily test the ProductService with xUnit or NUnit. For database tests, use a dedicated test database (not your production one) to avoid side effects.

Example xUnit Tests #

using Xunit;
using System.Data.SqlClient;

public class ProductServiceTests
{
    // Use a test database connection string (update this to match your setup)
    private readonly string _testConnectionString = "Server=localhost;Database=ProductTestDB;Trusted_Connection=True;";

    [Fact]
    public void AddProduct_WithMissingRequiredFields_ReturnsMissingInfoMessage()
    {
        // Arrange
        var service = new ProductService(_testConnectionString);

        // Act: Pass an empty product name
        var result = service.AddProduct("", "Electronics", "10", "50");

        // Assert
        Assert.Equal("Missing Information", result);
    }

    [Fact]
    public void AddProduct_WithValidData_ReturnsSuccessMessage()
    {
        // Arrange
        var service = new ProductService(_testConnectionString);
        string testProductName = "Test Wireless Mouse";

        // Act
        var result = service.AddProduct(testProductName, "Electronics", "20", "25");

        // Assert
        Assert.Equal("Product Added", result);

        // Optional: Verify the product was actually added to the database
        using (var con = new SqlConnection(_testConnectionString))
        {
            con.Open();
            var cmd = new SqlCommand("SELECT COUNT(*) FROM ProductTbl WHERE PrName = @PN", con);
            cmd.Parameters.AddWithValue("@PN", testProductName);
            int count = (int)cmd.ExecuteScalar();
            Assert.Equal(1, count);
        }
    }

    [Fact]
    public void DeleteProduct_WithZeroId_ReturnsSelectProductMessage()
    {
        // Arrange
        var service = new ProductService(_testConnectionString);

        // Act
        var result = service.DeleteProduct(0);

        // Assert
        Assert.Equal("Select an Product", result);
    }

    [Fact]
    public void DeleteProduct_WithValidId_ReturnsSuccessMessage()
    {
        // Arrange
        var service = new ProductService(_testConnectionString);
        // First add a test product to delete
        service.AddProduct("Test Keyboard", "Electronics", "15", "40");
        // Get the ID of the new product
        int productId = 0;
        using (var con = new SqlConnection(_testConnectionString))
        {
            con.Open();
            var cmd = new SqlCommand("SELECT PrId FROM ProductTbl WHERE PrName = @PN", con);
            cmd.Parameters.AddWithValue("@PN", "Test Keyboard");
            productId = (int)cmd.ExecuteScalar();
        }

        // Act
        var result = service.DeleteProduct(productId);

        // Assert
        Assert.Equal("Product Deleted", result);
        // Verify the product was removed
        using (var con = new SqlConnection(_testConnectionString))
        {
            con.Open();
            var cmd = new SqlCommand("SELECT COUNT(*) FROM ProductTbl WHERE PrId = @PKey", con);
            cmd.Parameters.AddWithValue("@PKey", productId);
            int count = (int)cmd.ExecuteScalar();
            Assert.Equal(0, count);
        }
    }
}

3. (Optional) UI Automation Testing for Button Clicks #

If you want to test the actual button click behavior (like verifying MessageBox pops up or UI updates), use a tool like WinAppDriver for UI automation. Here's a quick example:

using OpenQA.Selenium.Appium;
using OpenQA.Selenium.Appium.Windows;
using Xunit;

public class ProductFormUITests
{
    private WindowsDriver<WindowsElement> _driver;

    [Fact]
    public void SaveButton_Click_WithEmptyFields_ShowsMissingInfoMessageBox()
    {
        // Initialize WinAppDriver (make sure it's running in the background)
        var appOptions = new AppiumOptions();
        appOptions.AddAdditionalCapability("app", @"C:\Path\To\Your\WinFormsApp.exe");
        _driver = new WindowsDriver<WindowsElement>(new Uri("http://127.0.0.1:4723"), appOptions);

        // Find and click the save button
        var saveButton = _driver.FindElementByAccessibilityId("Savebtn");
        saveButton.Click();

        // Verify the message box appears with the correct text
        var messageBox = _driver.FindElementByClassName("#32770");
        var messageText = messageBox.FindElementByClassName("Static").Text;
        Assert.Equal("Missing Information", messageText);

        // Close the message box
        var okButton = messageBox.FindElementByName("OK");
        okButton.Click();

        // Clean up
        _driver.Quit();
    }
}

内容的提问来源于stack exchange，提问作者Dora99