Add a test for PurgeOrchestrationHistory

- Fix bug with PurgeOrchestrationHistory relating to null start date

src/WebJobs.Extensions.DurableTask/ProtobufUtils.cs

@@ -438,8 +438,10 @@ internal static PurgeInstanceFilter ToPurgeInstanceFilter(P.PurgeInstancesReques
                 statusFilter = request.PurgeInstanceFilter.RuntimeStatus?.Select(status => (OrchestrationStatus)status).ToList();
             }
 
+            // This ternary condition is necessary because the protobuf spec __insists__ that CreatedTimeFrom may never be null,
+            // but nonetheless if you pass null in function code, the value will be null here
             return new PurgeInstanceFilter(
-                request.PurgeInstanceFilter.CreatedTimeFrom.ToDateTime(),
+                request.PurgeInstanceFilter.CreatedTimeFrom == null ? DateTime.MinValue : request.PurgeInstanceFilter.CreatedTimeTo.ToDateTime(),
                 request.PurgeInstanceFilter.CreatedTimeTo?.ToDateTime(),
                 statusFilter);
         }

test/e2e/Apps/BasicDotNetIsolated/PurgeOrchestrationHistory.cs

@@ -0,0 +1,38 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+
+using System.Net;
+using Microsoft.Azure.Functions.Worker;
+using Microsoft.Azure.Functions.Worker.Http;
+using Microsoft.DurableTask.Client;
+using Microsoft.Extensions.Logging;
+
+namespace Microsoft.Azure.Durable.Tests.E2E
+{
+    public static class PurgeOrchestrationHistory
+    {
+        [Function(nameof(PurgeOrchestrationHistory))]
+        public static async Task<HttpResponseData> PurgeHistory(
+            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post")] HttpRequestData req,
+            [DurableClient] DurableTaskClient client,
+            FunctionContext executionContext)
+        {
+            ILogger logger = executionContext.GetLogger("HelloCities_HttpStart");
+
+            logger.LogInformation("Starting purge all instance history");
+
+            var requestPurgeResult = await client.PurgeAllInstancesAsync(new PurgeInstancesFilter(null, DateTime.UtcNow, new List<OrchestrationRuntimeStatus>{
+                OrchestrationRuntimeStatus.Completed,
+                OrchestrationRuntimeStatus.Failed,
+                OrchestrationRuntimeStatus.Terminated
+            }));
+
+            logger.LogInformation("Finished purge all instance history");
+
+            var response =  req.CreateResponse(HttpStatusCode.OK);
+            response.Headers.Add("Content-Type", "text/plain");
+            await response.WriteStringAsync($"Purged {requestPurgeResult.PurgedInstanceCount} records");
+            return response;
+        }
+    }
+}

test/e2e/Tests/Tests/PurgeInstancesTests.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net;
+using System.Text;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.Azure.Durable.Tests.DotnetIsolatedE2E;
+
+[Collection(Constants.FunctionAppCollectionName)]
+public class PurgeInstancesTests
+{
+    private readonly FunctionAppFixture _fixture;
+    private readonly ITestOutputHelper _output;
+
+    public PurgeInstancesTests(FunctionAppFixture fixture, ITestOutputHelper testOutputHelper)
+    {
+        _fixture = fixture;
+        _fixture.TestLogs.UseTestLogger(testOutputHelper);
+        _output = testOutputHelper;
+    }
+
+    // Due to some kind of asynchronous race condition in XUnit, when running these tests in pipelines,
+    // the output may be disposed before the message is written. Just ignore these types of errors for now. 
+    private void WriteOutput(string message)
+    {
+        try
+        {
+            _output.WriteLine(message);
+        }
+        catch
+        {
+            // Ignore
+        }
+    }
+
+    [Theory]
+    [InlineData("PurgeOrchestrationHistory", HttpStatusCode.OK, @"^Purged [0-9]* records$")]
+    public async Task HttpTriggerTests(string functionName, HttpStatusCode expectedStatusCode, string responseRegex)
+    {
+        using HttpResponseMessage response = await HttpHelpers.InvokeHttpTrigger(functionName, "");
+        string actualMessage = await response.Content.ReadAsStringAsync();
+        Assert.Matches(responseRegex, actualMessage);
+        Assert.Equal(expectedStatusCode, response.StatusCode);
+    }
+}