Add explicit test class for testing configuration without test appsettings

Author: ChrisDoernen

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

@@ -1,11 +1,11 @@
 namespace Xunit.Microsoft.DependencyInjection.ExampleTests;
 
-public class ConfigurationTests : TestBed<TestProjectFixtureWithoutAppsettings>
+public class ConfigurationTests : TestBed<TestProjectFixture>
 {
     private const string Key = "CONFIG_KEY";
     private const string Value = "Value";
 
-    public ConfigurationTests(ITestOutputHelper testOutputHelper, TestProjectFixtureWithoutAppsettings fixture) 
+    public ConfigurationTests(ITestOutputHelper testOutputHelper, TestProjectFixture fixture) 
         : base(testOutputHelper, fixture)
     {
         Environment.SetEnvironmentVariable(Key, Value);

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

@@ -0,0 +1,23 @@
+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);
+    }
+}