improve test coverage: InMemoryExporter SnapshotMetric

test/OpenTelemetry.Tests/Metrics/MetricSnapshotTests.cs

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+// <copyright file="MetricSnapshotTests.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 MetricSnapshotTests
+    {
+        [Fact]
+        public void VerifySnapshot_Counter()
+        {
+            var exportedMetrics = new List<Metric>();
+            var exportedSnapshots = new List<MetricSnapshot>();
+
+            using var meter = new Meter(Utils.GetCurrentMethodName());
+            var counter = meter.CreateCounter<long>("meter");
+            using var meterProvider = Sdk.CreateMeterProviderBuilder()
+                .AddMeter(meter.Name)
+                .AddInMemoryExporter(exportedMetrics)
+                .AddInMemoryExporter(exportedSnapshots)
+                .Build();
+
+            // FIRST EXPORT
+            counter.Add(10);
+            meterProvider.ForceFlush();
+
+            // Verify Metric 1
+            Assert.Single(exportedMetrics);
+            var metric1 = exportedMetrics[0];
+            var metricPoints1Enumerator = metric1.GetMetricPoints().GetEnumerator();
+            Assert.True(metricPoints1Enumerator.MoveNext());
+            ref readonly var metricPoint1 = ref metricPoints1Enumerator.Current;
+            Assert.Equal(10, metricPoint1.GetSumLong());
+
+            // Verify Snapshot 1
+            Assert.Single(exportedSnapshots);
+            var snapshot1 = exportedSnapshots[0];
+            Assert.Single(snapshot1.MetricPoints);
+            Assert.Equal(10, snapshot1.MetricPoints[0].GetSumLong());
+
+            // Verify Metric == Snapshot
+            Assert.Equal(metric1.Name, snapshot1.Name);
+            Assert.Equal(metric1.Description, snapshot1.Description);
+            Assert.Equal(metric1.Unit, snapshot1.Unit);
+            Assert.Equal(metric1.MeterName, snapshot1.MeterName);
+            Assert.Equal(metric1.MetricType, snapshot1.MetricType);
+            Assert.Equal(metric1.MeterVersion, snapshot1.MeterVersion);
+
+            // SECOND EXPORT
+            counter.Add(5);
+            meterProvider.ForceFlush();
+
+            // Verify Metric 1, after second export
+            // This value is expected to be updated.
+            Assert.Equal(15, metricPoint1.GetSumLong());
+
+            // Verify Metric 2
+            Assert.Equal(2, exportedMetrics.Count);
+            var metric2 = exportedMetrics[1];
+            var metricPoints2Enumerator = metric2.GetMetricPoints().GetEnumerator();
+            Assert.True(metricPoints2Enumerator.MoveNext());
+            ref readonly var metricPoint2 = ref metricPoints2Enumerator.Current;
+            Assert.Equal(15, metricPoint2.GetSumLong());
+
+            // Verify Snapshot 1, after second export
+            // This value is expected to be unchanged.
+            Assert.Equal(10, snapshot1.MetricPoints[0].GetSumLong());
+
+            // Verify Snapshot 2
+            Assert.Equal(2, exportedSnapshots.Count);
+            var snapshot2 = exportedSnapshots[1];
+            Assert.Single(snapshot2.MetricPoints);
+            Assert.Equal(15, snapshot2.MetricPoints[0].GetSumLong());
+        }
+
+        [Fact]
+        public void VerifySnapshot_Histogram()
+        {
+            var exportedMetrics = new List<Metric>();
+            var exportedSnapshots = new List<MetricSnapshot>();
+
+            using var meter = new Meter(Utils.GetCurrentMethodName());
+            var histogram = meter.CreateHistogram<int>("histogram");
+            using var meterProvider = Sdk.CreateMeterProviderBuilder()
+                .AddMeter(meter.Name)
+                .AddInMemoryExporter(exportedMetrics)
+                .AddInMemoryExporter(exportedSnapshots)
+                .Build();
+
+            // FIRST EXPORT
+            histogram.Record(10);
+            meterProvider.ForceFlush();
+
+            // Verify Metric 1
+            Assert.Single(exportedMetrics);
+            var metric1 = exportedMetrics[0];
+            var metricPoints1Enumerator = metric1.GetMetricPoints().GetEnumerator();
+            Assert.True(metricPoints1Enumerator.MoveNext());
+            ref readonly var metricPoint1 = ref metricPoints1Enumerator.Current;
+            Assert.Equal(1, metricPoint1.GetHistogramCount());
+            Assert.Equal(10, metricPoint1.GetHistogramSum());
+
+            // Verify Snapshot 1
+            Assert.Single(exportedSnapshots);
+            var snapshot1 = exportedSnapshots[0];
+            Assert.Single(snapshot1.MetricPoints);
+            Assert.Equal(1, snapshot1.MetricPoints[0].GetHistogramCount());
+            Assert.Equal(10, snapshot1.MetricPoints[0].GetHistogramSum());
+
+            // Verify Metric == Snapshot
+            Assert.Equal(metric1.Name, snapshot1.Name);
+            Assert.Equal(metric1.Description, snapshot1.Description);
+            Assert.Equal(metric1.Unit, snapshot1.Unit);
+            Assert.Equal(metric1.MeterName, snapshot1.MeterName);
+            Assert.Equal(metric1.MetricType, snapshot1.MetricType);
+            Assert.Equal(metric1.MeterVersion, snapshot1.MeterVersion);
+
+            // SECOND EXPORT
+            histogram.Record(5);
+            meterProvider.ForceFlush();
+
+            // Verify Metric 1 after second export
+            // This value is expected to be updated.
+            Assert.Equal(2, metricPoint1.GetHistogramCount());
+            Assert.Equal(15, metricPoint1.GetHistogramSum());
+
+            // Verify Metric 2
+            Assert.Equal(2, exportedMetrics.Count);
+            var metric2 = exportedMetrics[1];
+            var metricPoints2Enumerator = metric2.GetMetricPoints().GetEnumerator();
+            Assert.True(metricPoints2Enumerator.MoveNext());
+            ref readonly var metricPoint2 = ref metricPoints2Enumerator.Current;
+            Assert.Equal(2, metricPoint2.GetHistogramCount());
+            Assert.Equal(15, metricPoint2.GetHistogramSum());
+
+            // Verify Snapshot 1 after second export
+            // This value is expected to be unchanged.
+            Assert.Equal(1, snapshot1.MetricPoints[0].GetHistogramCount());
+            Assert.Equal(10, snapshot1.MetricPoints[0].GetHistogramSum());
+
+            // Verify Snapshot 2
+            Assert.Equal(2, exportedSnapshots.Count);
+            var snapshot2 = exportedSnapshots[1];
+            Assert.Single(snapshot2.MetricPoints);
+            Assert.Equal(2, snapshot2.MetricPoints[0].GetHistogramCount());
+            Assert.Equal(15, snapshot2.MetricPoints[0].GetHistogramSum());
+        }
+    }
+}