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Merge pull request #310 from Umplify/copilot/fix-79448302-d339-4707-af35-00806c9f5383
Implement constructor dependency injection while maintaining existing fixture patterns
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‎CONSTRUCTOR_INJECTION.md‎

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# Constructor Dependency Injection
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This document describes the new constructor dependency injection capabilities added to the xUnit Dependency Injection framework while maintaining full backward compatibility with the existing fixture-based approach.
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## Overview
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The framework now supports two approaches for dependency injection:
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1. **Traditional Fixture-Based Approach** (existing) - Access services via `_fixture.GetService<T>(_testOutputHelper)`
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2. **Constructor Dependency Injection** (new) - Inject services directly into test class properties during construction
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## Property Injection with TestBedWithDI
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### Basic Usage
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Inherit from `TestBedWithDI<TFixture>` instead of `TestBed<TFixture>` and use the `[Inject]` attribute on properties:
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```csharp
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public class PropertyInjectionTests : TestBedWithDI<TestProjectFixture>
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{
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[Inject]
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public ICalculator? Calculator { get; set; }
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[Inject]
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public IOptions<Options>? Options { get; set; }
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public PropertyInjectionTests(ITestOutputHelper testOutputHelper, TestProjectFixture fixture)
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: base(testOutputHelper, fixture)
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{
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// Dependencies are automatically injected after base constructor completes
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}
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[Fact]
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public async Task TestCalculatorThroughPropertyInjection()
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{
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// Dependencies are already available - no need to call _fixture methods
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Assert.NotNull(Calculator);
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Assert.NotNull(Options);
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var result = await Calculator.AddAsync(5, 3);
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var expected = Options.Value.Rate * (5 + 3);
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Assert.Equal(expected, result);
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}
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}
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```
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### Keyed Services
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Use the `[Inject("key")]` attribute for keyed services:
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```csharp
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public class PropertyInjectionTests : TestBedWithDI<TestProjectFixture>
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{
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[Inject("Porsche")]
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internal ICarMaker? PorscheCarMaker { get; set; }
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[Inject("Toyota")]
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internal ICarMaker? ToyotaCarMaker { get; set; }
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[Fact]
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public void TestKeyedServicesThroughPropertyInjection()
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{
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Assert.NotNull(PorscheCarMaker);
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Assert.NotNull(ToyotaCarMaker);
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Assert.Equal("Porsche", PorscheCarMaker.Manufacturer);
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Assert.Equal("Toyota", ToyotaCarMaker.Manufacturer);
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}
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}
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```
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### Convenience Methods
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The `TestBedWithDI` class provides convenience methods that don't require the `_testOutputHelper` parameter:
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```csharp
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protected T? GetService<T>()
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protected T? GetScopedService<T>()
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protected T? GetKeyedService<T>(string key)
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```
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```csharp
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[Theory]
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[InlineData(10, 20)]
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public async Task TestConvenienceMethodsStillWork(int x, int y)
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{
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// These methods are available without needing _fixture
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var calculator = GetService<ICalculator>();
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var options = GetService<IOptions<Options>>();
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var porsche = GetKeyedService<ICarMaker>("Porsche");
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Assert.NotNull(calculator);
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Assert.NotNull(options);
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Assert.NotNull(porsche);
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}
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```
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## Factory-Based Constructor Injection (Experimental)
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For true constructor injection, use `TestBedFactoryFixture` with the factory pattern:
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### Setup
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```csharp
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public class FactoryTestProjectFixture : TestBedFactoryFixture
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{
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protected override void AddServices(IServiceCollection services, IConfiguration? configuration)
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=> services
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.AddTransient<ICalculator, Calculator>()
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.AddKeyedTransient<ICarMaker, Porsche>("Porsche")
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.AddKeyedTransient<ICarMaker, Toyota>("Toyota")
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.AddTransient<SimpleService>(); // Register classes that need constructor injection
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}
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```
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### Usage
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```csharp
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public class FactoryConstructorInjectionTests : TestBed<FactoryTestProjectFixture>
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{
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[Fact]
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public async Task TestConstructorInjectionViaFactory()
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{
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// Create instances with constructor injection
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var simpleService = _fixture.CreateTestInstance<SimpleService>(_testOutputHelper);
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var result = await simpleService.CalculateAsync(10, 5);
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Assert.True(result > 0);
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}
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}
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```
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### Service Class with Constructor Injection
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```csharp
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public class SimpleService
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{
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private readonly ICalculator _calculator;
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private readonly Options _options;
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public SimpleService(ICalculator calculator, IOptions<Options> options)
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{
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_calculator = calculator ?? throw new ArgumentNullException(nameof(calculator));
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_options = options?.Value ?? throw new ArgumentNullException(nameof(options));
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}
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public async Task<int> CalculateAsync(int x, int y)
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{
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return await _calculator.AddAsync(x, y);
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}
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}
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```
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### Keyed Services in Factory Pattern
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Use the `[FromKeyedService("key")]` attribute for keyed service constructor parameters:
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```csharp
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public class CalculatorService
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{
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public CalculatorService(
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ICalculator calculator,
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IOptions<Options> options,
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[FromKeyedService("Porsche")] ICarMaker porsche,
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[FromKeyedService("Toyota")] ICarMaker toyota)
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{
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// Constructor injection with keyed services
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}
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}
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```
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## Backward Compatibility
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All existing code continues to work unchanged. The new approaches are additive:
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- `TestBed<TFixture>` continues to work as before
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- `_fixture.GetService<T>(_testOutputHelper)` methods work as before
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- Existing test classes require no changes
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## Migration Path
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You can migrate existing tests gradually:
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1. **Option 1**: Keep using `TestBed<TFixture>` with existing fixture methods
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2. **Option 2**: Change to `TestBedWithDI<TFixture>` and use `[Inject]` properties for new dependencies while keeping existing fixture method calls
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3. **Option 3**: Fully migrate to property injection for cleaner test code
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## Benefits
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### Property Injection Approach
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- ✅ Clean, declarative syntax
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- ✅ No need to pass `_testOutputHelper` around
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- ✅ Dependencies available immediately in test methods
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- ✅ Full support for regular and keyed services
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- ✅ Maintains all existing fixture capabilities
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- ✅ Works perfectly with xUnit lifecycle
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### Factory Approach
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- ✅ True constructor injection for service classes
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- ✅ Works for regular services and additional parameters
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- ⚠️ Keyed services support is experimental
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- ⚠️ More complex setup required
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## Recommendation
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Use the **Property Injection with TestBedWithDI** approach for most scenarios as it provides the cleanest developer experience while maintaining full compatibility with the existing framework.

‎README.md‎

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Xunit does not support any built-in dependency injection features, therefore developers have to come up with a solution to recruit their favourite dependency injection framework in their tests.
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This library brings in Microsoft's dependency injection container to Xunit by leveraging Xunit's fixture.
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This library brings Microsoft's dependency injection container to Xunit by leveraging Xunit's fixture pattern and now supports **two approaches** for dependency injection:
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1. **Traditional Fixture-Based Approach** - Access services via `_fixture.GetService<T>(_testOutputHelper)` (fully supported, backward compatible)
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2. **Constructor Dependency Injection** - Inject services directly into test class properties using the `[Inject]` attribute (new feature)
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## Important: xUnit versions
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T? GetKeyedService<T>([DisallowNull] string key, ITestOutputHelper testOutputHelper);
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```
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## Constructor Dependency Injection
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**New in this version (ver 9.2.0 and beyond)**: The library now supports constructor-style dependency injection while maintaining full backward compatibility with the existing fixture-based approach.
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### Property Injection with TestBedWithDI (Recommended)
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For cleaner test code, inherit from `TestBedWithDI<TFixture>` instead of `TestBed<TFixture>` and use the `[Inject]` attribute:
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```csharp
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public class PropertyInjectionTests : TestBedWithDI<TestProjectFixture>
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{
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[Inject]
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public ICalculator? Calculator { get; set; }
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[Inject]
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public IOptions<Options>? Options { get; set; }
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public PropertyInjectionTests(ITestOutputHelper testOutputHelper, TestProjectFixture fixture)
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: base(testOutputHelper, fixture)
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{
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// Dependencies are automatically injected after construction
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}
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[Fact]
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public async Task TestWithCleanSyntax()
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{
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// Dependencies are immediately available - no fixture calls needed
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Assert.NotNull(Calculator);
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var result = await Calculator.AddAsync(5, 3);
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Assert.True(result > 0);
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}
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}
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```
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### Keyed Services with Property Injection
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Use the `[Inject("key")]` attribute for keyed services:
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```csharp
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public class PropertyInjectionTests : TestBedWithDI<TestProjectFixture>
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{
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[Inject("Porsche")]
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internal ICarMaker? PorscheCarMaker { get; set; }
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[Inject("Toyota")]
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internal ICarMaker? ToyotaCarMaker { get; set; }
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[Fact]
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public void TestKeyedServices()
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{
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Assert.NotNull(PorscheCarMaker);
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Assert.NotNull(ToyotaCarMaker);
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Assert.Equal("Porsche", PorscheCarMaker.Manufacturer);
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Assert.Equal("Toyota", ToyotaCarMaker.Manufacturer);
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}
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}
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```
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### Convenience Methods
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The `TestBedWithDI` class provides convenience methods that don't require the `_testOutputHelper` parameter:
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```csharp
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protected T? GetService<T>()
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protected T? GetScopedService<T>()
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protected T? GetKeyedService<T>(string key)
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```
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### Benefits of Constructor Dependency Injection
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- ✅ **Clean, declarative syntax** - Use `[Inject]` attribute on properties
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- ✅ **No manual fixture calls** - Dependencies available immediately in test methods
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- ✅ **Full keyed services support** - Both regular and keyed services work seamlessly
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- ✅ **Backward compatible** - All existing `TestBed<TFixture>` code continues to work unchanged
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- ✅ **Gradual migration** - Adopt new approach incrementally without breaking existing tests
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### Migration Guide
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You can migrate existing tests gradually:
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1. **Keep existing approach** - Continue using `TestBed<TFixture>` with fixture methods
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2. **Hybrid approach** - Change to `TestBedWithDI<TFixture>` and use both `[Inject]` properties and fixture methods
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3. **Full migration** - Use property injection for all dependencies for cleanest code
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### Factory Pattern (Experimental)
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For true constructor injection into service classes, see [CONSTRUCTOR_INJECTION.md](CONSTRUCTOR_INJECTION.md) for the factory-based approach.
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### Adding custom logging provider
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Test developers can add their own desired logger provider by overriding ```AddLoggingProvider(...)``` virtual method defined in ```TestBedFixture``` class.
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## Examples
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* Please [follow this link](https://github.com/Umplify/xunit-dependency-injection/tree/main/examples/Xunit.Microsoft.DependencyInjection.ExampleTests) to view a couple of examples on utilizing this library.
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* Please [follow this link](https://github.com/Umplify/xunit-dependency-injection/tree/main/examples/Xunit.Microsoft.DependencyInjection.ExampleTests) to view examples utilizing both the traditional fixture-based approach and the new constructor dependency injection features.
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* **Traditional approach**: See examples using `TestBed<TFixture>` and `_fixture.GetService<T>(_testOutputHelper)`
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* **Constructor injection**: See `PropertyInjectionTests.cs` for examples using `TestBedWithDI<TFixture>` with `[Inject]` attributes
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* **Factory pattern**: See `FactoryConstructorInjectionTests.cs` for experimental constructor injection scenarios
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* [Digital Silo](https://digitalsilo.io/)'s unit tests and integration tests are using this library.
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### One more thing

‎azure-pipelines.yml‎

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variables:
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Major: 9
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Minor: 1
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Revision: 2
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Minor: 2
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Revision: 0
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BuildConfiguration: Release
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name: $(Major).$(Minor).$(Revision)
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command: 'build'
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projects: '**/Xunit.Microsoft.DependencyInjection.csproj'
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arguments: '--configuration $(BuildConfiguration)'
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# Pack (with symbols & SourceLink) happens before publish to ensure packages are available as build artifacts
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- script: echo Packing library with symbols and SourceLink metadata
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displayName: 'Pre-Pack Info'
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- task: DotNetCoreCLI@2
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displayName: 'Packing (nupkg + snupkg)'
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inputs:
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command: 'pack'
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packagesToPack: '**/Xunit.Microsoft.DependencyInjection.csproj'
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arguments: '--configuration $(BuildConfiguration) /p:ContinuousIntegrationBuild=true /p:IncludeSymbols=true /p:SymbolPackageFormat=snupkg --output $(Build.ArtifactStagingDirectory)/packages'
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nobuild: true
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- task: DotNetCoreCLI@2
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displayName: 'Running tests in example folder'
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continueOnError: true
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- script: echo Started packing and pushing
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- task: NuGetCommand@2
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displayName: 'Packing'
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- task: PublishBuildArtifacts@1
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displayName: 'Publish Packages'
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inputs:
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command: 'pack'
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packagesToPack: '**/Xunit.Microsoft.DependencyInjection.csproj'
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versioningScheme: 'byEnvVar'
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versionEnvVar: 'Build.BuildNumber'
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PathtoPublish: '$(Build.ArtifactStagingDirectory)/packages'
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ArtifactName: 'packages'
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publishLocation: 'Container'
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# Push both nupkg & snupkg (exclude legacy symbols.nupkg)
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- task: NuGetCommand@2
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displayName: 'Pushing to nuget.org'
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inputs:
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command: 'push'
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packagesToPush: '$(Build.ArtifactStagingDirectory)/**/*.nupkg;!$(Build.ArtifactStagingDirectory)/**/*.symbols.nupkg'
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packagesToPush: '$(Build.ArtifactStagingDirectory)/packages/**/*.nupkg;$(Build.ArtifactStagingDirectory)/packages/**/*.snupkg'
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nuGetFeedType: 'external'
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publishFeedCredentials: 'NuGet'
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allowPackageConflicts: true

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