bUnit is the standard testing library for Blazor components. It lets you render components in isolation, interact with them, and assert on their output.

Setup

// Install:
// dotnet add package bunit
// dotnet add package xunit

// Test class:
public class CounterTests : TestContext
{
    [Fact]
    public void Counter_IncrementsOnButtonClick()
    {
        // Arrange
        var cut = RenderComponent<Counter>();

        // Act
        cut.Find("button").Click();

        // Assert
        cut.Find("p").TextContent
           .MarkupMatches("Current count: 1");
    }
}

Providing Parameters

var cut = RenderComponent<ProductCard>(parameters => parameters
    .Add(p => p.Product, new Product { Name = "Laptop", Price = 999 }));

Mocking Services

Services.AddSingleton<IProductService>(mockService);
var cut = RenderComponent<ProductList>();

What to Test

• Component renders correct initial state
• UI updates after user interaction
• Conditional rendering (shown/hidden elements)
• EventCallback invocations

Reference:

Wikipedia: Unit Testing

https://en.wikipedia.org/wiki/Unit_testing