chore(): Enable CA-only mTLS configuration and expand tests

Author: sandy2008

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/OtlpMtlsOptions.cs

@@ -30,9 +30,11 @@ internal sealed class OtlpMtlsOptions
 
     /// <summary>
     /// Gets a value indicating whether mTLS is enabled.
-    /// mTLS is considered enabled if at least the client certificate path is provided.
+    /// mTLS is considered enabled if at least the client certificate path or CA certificate path is provided.
     /// </summary>
-    public bool IsEnabled => !string.IsNullOrWhiteSpace(this.ClientCertificatePath);
+    public bool IsEnabled =>
+        !string.IsNullOrWhiteSpace(this.ClientCertificatePath)
+        || !string.IsNullOrWhiteSpace(this.CaCertificatePath);
 }
 
 #endif

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpExporterOptionsTests.cs

@@ -276,6 +276,7 @@ public void OtlpExporterOptions_MtlsEnvironmentVariables()
 
             Assert.NotNull(options.MtlsOptions);
             Assert.Equal("/path/to/ca.crt", options.MtlsOptions.CaCertificatePath);
+            Assert.True(options.MtlsOptions.IsEnabled);
         }
         finally
         {

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpMtlsCertificateManagerTests.cs

@@ -3,8 +3,6 @@
 
 #if NET
 
-using Xunit;
-
 namespace OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests;
 
 public class OtlpMtlsCertificateManagerTests

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpMtlsHttpClientFactoryTests.cs

@@ -3,8 +3,6 @@
 
 #if NET
 
-using Xunit;
-
 namespace OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests;
 
 public class OtlpMtlsHttpClientFactoryTests
@@ -78,10 +76,7 @@ public void CreateHttpClient_ConfiguresServerCertificateValidation_WhenTrustedRo
         {
             // Create a self-signed certificate for testing as trusted root
             using var trustedCert = CreateSelfSignedCertificate();
-            var trustedCertPem = Convert.ToBase64String(trustedCert.Export(System.Security.Cryptography.X509Certificates.X509ContentType.Cert));
-            var pemContent =
-                $"-----BEGIN CERTIFICATE-----\n{trustedCertPem}\n-----END CERTIFICATE-----";
-            File.WriteAllText(tempTrustStoreFile, pemContent);
+            File.WriteAllText(tempTrustStoreFile, trustedCert.ExportCertificatePem());
 
             var options = new OtlpMtlsOptions
             {

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpMtlsOptionsTests.cs

@@ -3,8 +3,6 @@
 
 #if NET
 
-using Xunit;
-
 namespace OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests;
 
 public class OtlpMtlsOptionsTests
@@ -46,6 +44,22 @@ public void IsEnabled_ReturnsFalse_WhenNoClientCertificateProvided()
         Assert.False(options.IsEnabled);
     }
 
+    [Fact]
+    public void IsEnabled_ReturnsTrue_WhenCaCertificateFilePathProvided()
+    {
+        var options = new OtlpMtlsOptions { CaCertificatePath = "/path/to/ca.crt" };
+        Assert.True(options.IsEnabled);
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData("   ")]
+    public void IsEnabled_ReturnsFalse_WhenCaCertificateFilePathIsEmpty(string filePath)
+    {
+        var options = new OtlpMtlsOptions { CaCertificatePath = filePath };
+        Assert.False(options.IsEnabled);
+    }
+
     [Fact]
     public void IsEnabled_ReturnsTrue_WhenClientCertificateFilePathProvided()
     {

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpSpecConfigDefinitionsTests.cs

@@ -3,8 +3,6 @@
 
 #if NET
 
-using Xunit;
-
 namespace OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests;
 
 public class OtlpSpecConfigDefinitionsTests