feat: execute post-baseline jetstream parity plan

tests/NATS.Server.Tests/JetStreamConsumerFlowControlParityTests.cs

@@ -0,0 +1,41 @@
+using NATS.Server.JetStream;
+using NATS.Server.JetStream.Models;
+
+namespace NATS.Server.Tests;
+
+public class JetStreamConsumerFlowControlParityTests
+{
+    [Fact]
+    public async Task Push_consumer_emits_flow_control_frames_when_enabled()
+    {
+        var streams = new StreamManager();
+        streams.CreateOrUpdate(new StreamConfig
+        {
+            Name = "ORDERS",
+            Subjects = ["orders.*"],
+        });
+
+        var consumers = new ConsumerManager();
+        consumers.CreateOrUpdate("ORDERS", new ConsumerConfig
+        {
+            DurableName = "PUSH",
+            Push = true,
+            AckPolicy = AckPolicy.Explicit,
+            FlowControl = true,
+            RateLimitBps = 1024,
+        });
+
+        var ack = streams.Capture("orders.created", "x"u8.ToArray());
+        streams.TryGet("ORDERS", out var stream).ShouldBeTrue();
+        var message = await stream.Store.LoadAsync(ack!.Seq, default);
+        message.ShouldNotBeNull();
+        consumers.OnPublished("ORDERS", message!);
+
+        var first = consumers.ReadPushFrame("ORDERS", "PUSH");
+        var second = consumers.ReadPushFrame("ORDERS", "PUSH");
+        first.ShouldNotBeNull();
+        second.ShouldNotBeNull();
+        first!.IsData.ShouldBeTrue();
+        second!.IsFlowControl.ShouldBeTrue();
+    }
+}