Make configuration work independent of whether appsettings json files are provided

azure-pipeline-PR.yml

@@ -1,7 +1,7 @@
 variables:
   Major: 10
   Minor: 0
-  Patch: 1
+  Patch: 2
   BuildConfiguration: Release
 
 name: $(Major).$(Minor).$(Patch).$(rev:r)
@@ -17,7 +17,7 @@ steps:
   displayName: 'Use .NET 10.0 sdk'
   inputs:
     packageType: sdk
-    version: 10.0.100
+    version: 10.0.101
     installationPath: $(Agent.ToolsDirectory)/dotnet
 - script: echo Started restoring the source code
 - task: DotNetCoreCLI@2

azure-pipelines.yml

@@ -1,7 +1,7 @@
 variables:
   Major: 10
   Minor: 0
-  Revision: 1
+  Revision: 2
   BuildConfiguration: Release
 
 name: $(Major).$(Minor).$(Revision)
@@ -25,7 +25,7 @@ steps:
   displayName: 'Use .NET 10.0 sdk'
   inputs:
     packageType: sdk
-    version: 10.0.100
+    version: 10.0.101
     installationPath: $(Agent.ToolsDirectory)/dotnet
 - script: echo Started restoring the source code
 - task: DotNetCoreCLI@2

examples/Xunit.Microsoft.DependencyInjection.ExampleTests/ConfigurationTests.cs

@@ -5,7 +5,8 @@ public class ConfigurationTests : TestBed<TestProjectFixture>
     private const string Key = "CONFIG_KEY";
     private const string Value = "Value";
 
-    public ConfigurationTests(ITestOutputHelper testOutputHelper, TestProjectFixture fixture) : base(testOutputHelper, fixture)
+    public ConfigurationTests(ITestOutputHelper testOutputHelper, TestProjectFixture fixture) 
+        : base(testOutputHelper, fixture)
     {
         Environment.SetEnvironmentVariable(Key, Value);
     }

examples/Xunit.Microsoft.DependencyInjection.ExampleTests/ConfigurationTestsWithoutAppsettings.cs

@@ -0,0 +1,21 @@
+namespace Xunit.Microsoft.DependencyInjection.ExampleTests;
+
+public class ConfigurationTestsWithoutAppsettings : TestBed<TestProjectFixtureWithoutAppsettings>
+{
+    private const string Key = "CONFIG_KEY";
+    private const string Value = "Value";
+
+    public ConfigurationTestsWithoutAppsettings(ITestOutputHelper testOutputHelper, TestProjectFixtureWithoutAppsettings fixture) 
+        : base(testOutputHelper, fixture)
+    {
+        Environment.SetEnvironmentVariable(Key, Value);
+    }
+
+    [Fact]
+    public void EnvironmentVariablesViaConstructorAreAvailable()
+    {
+        _fixture.GetServiceProvider(_testOutputHelper);
+        var value = _fixture.Configuration!.GetValue<string>(Key);
+        Assert.Equal(Value, value);
+    }
+}

examples/Xunit.Microsoft.DependencyInjection.ExampleTests/Fixtures/TestProjectFixture.cs

@@ -2,7 +2,7 @@
 
 public class TestProjectFixture : TestBedFixture
 {
-    protected override void AddServices(IServiceCollection services, IConfiguration? configuration)
+    protected override void AddServices(IServiceCollection services, IConfiguration configuration)
         => services
         // Transient services - new instance for each injection
         .AddTransient<ICalculator, Calculator>()
@@ -23,8 +23,8 @@ protected override void AddServices(IServiceCollection services, IConfiguration?
         .AddTransient<Func<ISingletonService>>(provider => () => provider.GetService<ISingletonService>()!)
 
         // Configure options
-        .Configure<Options>(config => configuration?.GetSection("Options").Bind(config))
-        .Configure<SecretValues>(config => configuration?.GetSection(nameof(SecretValues)).Bind(config));
+        .Configure<Options>(config => configuration.GetSection("Options").Bind(config))
+        .Configure<SecretValues>(config => configuration.GetSection(nameof(SecretValues)).Bind(config));
 
     protected override ValueTask DisposeAsyncCore()
         => new();

examples/Xunit.Microsoft.DependencyInjection.ExampleTests/Fixtures/TestProjectFixtureWithoutAppsettings.cs

@@ -0,0 +1,10 @@
+namespace Xunit.Microsoft.DependencyInjection.ExampleTests.Fixtures;
+
+public class TestProjectFixtureWithoutAppsettings : TestBedFixture
+{
+  protected override void AddServices(IServiceCollection services, IConfiguration configuration)
+  {
+  }
+
+  protected override ValueTask DisposeAsyncCore() => new();
+}

src/Abstracts/TestBedFixture.cs

@@ -123,12 +123,12 @@ public async ValueTask DisposeAsync()
 	/// <summary>
 	/// Adds services to the service collection. Called once before building the provider.
 	/// </summary>
-	protected abstract void AddServices(IServiceCollection services, IConfiguration? configuration);
+	protected abstract void AddServices(IServiceCollection services, IConfiguration configuration);
 
 	/// <summary>
 	/// Returns the test application settings descriptors (JSON files) to include.
 	/// </summary>
-	protected abstract IEnumerable<TestAppSettings> GetTestAppSettings();
+	protected virtual IEnumerable<TestAppSettings> GetTestAppSettings() => [];
 
 	/// <summary>
 	/// Override to asynchronously clean up resources created by the fixture.
@@ -147,18 +147,15 @@ protected virtual ILoggingBuilder AddLoggingProvider(ILoggingBuilder loggingBuil
 	/// </summary>
 	protected virtual void AddUserSecrets(IConfigurationBuilder configurationBuilder) { }
 
-	private IConfigurationRoot? GetConfigurationRoot()
+	private IConfigurationRoot GetConfigurationRoot()
 	{
 		var testAppSettings = GetTestAppSettings();
-		return
-			testAppSettings.All(setting => !string.IsNullOrEmpty(setting.Filename))
-			? GetConfigurationRoot(testAppSettings)
-			: default;
+		return GetConfigurationRoot(testAppSettings);
 	}
 
 	private IConfigurationRoot GetConfigurationRoot(IEnumerable<TestAppSettings> configurationFiles)
 	{
-		foreach (var configurationFile in configurationFiles)
+		foreach (var configurationFile in configurationFiles.Where(appSetting => !string.IsNullOrEmpty(appSetting.Filename)))
 		{
 			ConfigurationBuilder.AddJsonFile(configurationFile.Filename!, optional: configurationFile.IsOptional);
 		}