Add a simple memory efficient test for metrics SDK (#2530)

test/OpenTelemetry.Tests/Metrics/MemoryEfficiencyTests.cs

@@ -0,0 +1,49 @@
+// <copyright file="MemoryEfficiencyTests.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+using System.Collections.Generic;
+using System.Diagnostics.Metrics;
+using OpenTelemetry.Tests;
+using Xunit;
+
+namespace OpenTelemetry.Metrics.Tests
+{
+    public class MemoryEfficiencyTests
+    {
+        [Fact(Skip = "To be run after https://github.com/open-telemetry/opentelemetry-dotnet/issues/2361 is fixed")]
+        public void CumulativeOnlyExportWhenPointChanged()
+        {
+            using var meter = new Meter(Utils.GetCurrentMethodName(), "1.0");
+
+            var exportedItems = new List<Metric>();
+
+            using var meterProvider = Sdk.CreateMeterProviderBuilder()
+                .AddMeter(meter.Name)
+                .AddInMemoryExporter(exportedItems)
+                .Build();
+
+            var counter = meter.CreateCounter<long>("meter");
+
+            counter.Add(10, new KeyValuePair<string, object>("tag1", "value1"));
+            meterProvider.ForceFlush();
+            Assert.Single(exportedItems);
+
+            exportedItems.Clear();
+            meterProvider.ForceFlush();
+            Assert.Empty(exportedItems);
+        }
+    }
+}

test/OpenTelemetry.Tests/Shared/Utils.cs

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+// <copyright file="Utils.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+
+namespace OpenTelemetry.Tests
+{
+    internal class Utils
+    {
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        public static string GetCurrentMethodName()
+        {
+            var method = new StackFrame(1).GetMethod();
+            return $"{method.DeclaringType.FullName}.{method.Name}";
+        }
+    }
+}