Add a test that demonstrates how to track the states of circuit break…

…er (#1829)

test/Polly.Core.Tests/Issues/IssuesTests.CircuitBreakerStateRegistry_1828.cs

@@ -0,0 +1,47 @@
+using Polly.CircuitBreaker;
+using Polly.Registry;
+
+namespace Polly.Core.Tests.Issues;
+
+public partial class IssuesTests
+{
+    [Fact]
+    public void CircuitBreakerStateRegistry_1828()
+    {
+        // Arrange
+        var states = new ConcurrentBag<CircuitBreakerStateProvider>();
+        using var registry = new ResiliencePipelineRegistry<string>();
+
+        // Act
+        _ = registry.GetOrAddPipeline("A", builder =>
+        {
+            var stateProvider = new CircuitBreakerStateProvider();
+            builder.AddCircuitBreaker(new() { StateProvider = stateProvider });
+            states.Add(stateProvider);
+        });
+
+        _ = registry.GetOrAddPipeline("B", builder =>
+        {
+            var stateProvider = new CircuitBreakerStateProvider();
+            builder.AddCircuitBreaker(new() { StateProvider = stateProvider });
+            states.Add(stateProvider);
+        });
+
+        _ = registry.TryAddBuilder("C", (builder, _) =>
+        {
+            var stateProvider = new CircuitBreakerStateProvider();
+            builder.AddCircuitBreaker(new() { StateProvider = stateProvider });
+            states.Add(stateProvider);
+        });
+
+        // Assert
+        states.Should().HaveCount(2);
+        registry.GetPipeline("C");
+        states.Should().HaveCount(3);
+
+        foreach (var state in states)
+        {
+            state.CircuitState.Should().Be(CircuitState.Closed);
+        }
+    }
+}