fix: try to make tests less flaky on macos

Author: natemcmaster

test/LettuceEncrypt.UnitTests/FileSystemCertificateRepoTests.cs

@@ -4,7 +4,6 @@
 #nullable enable
 using System.Security.Cryptography.X509Certificates;
 using LettuceEncrypt.Internal;
-using McMaster.Extensions.Xunit;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Hosting.Internal;
@@ -16,8 +15,7 @@ namespace LettuceEncrypt.UnitTests;
 
 public class FileSystemCertificateRepoTests
 {
-    [SkippableTheory]
-    [SkipOnOS(OS.MacOS)] // started failing with macOS 12. I don't really know why. If this matters to you, please send a PR to fix.
+    [Theory]
     [InlineData(null)]
     [InlineData("")]
     public async Task ItCanSaveCertsWithoutPassword(string? password)

test/LettuceEncrypt.UnitTests/TestUtils.cs

@@ -35,7 +35,31 @@ public static X509Certificate2 CreateTestCert(string[] domainNames, DateTimeOffs
         }
 
         var cert = csr.CreateSelfSigned(DateTimeOffset.Now.AddMinutes(-1), expires.Value);
-        // https://github.com/dotnet/runtime/issues/29144
-        return new X509Certificate2(cert.Export(X509ContentType.Pfx), "", X509KeyStorageFlags.PersistKeySet | X509KeyStorageFlags.Exportable);
+        int retries = 5;
+        while (retries > 0)
+        {
+            try
+            {
+                // https://github.com/dotnet/runtime/issues/29144
+                var certWithKey = cert.Export(X509ContentType.Pfx);
+                return new X509Certificate2(certWithKey, "", X509KeyStorageFlags.PersistKeySet | X509KeyStorageFlags.Exportable);
+            }
+            catch
+            {
+                retries--;
+                if (retries > 0)
+                {
+                    // For unclear reasons, on macOS it takes times for certs to be available for re-export.
+                    // Retries appear to work.
+                    Thread.Sleep(50);
+                    continue;
+                }
+                else
+                {
+                    throw;
+                }
+            }
+        }
+        throw new Exception($"Could not create self signed cert for {domainNames}");
     }
 }