added tests. MaxValueAggregator reset max value on read.

Author: bryce-b

Sources/OpenTelemetrySdk/Metrics/Aggregators/MaxValueAggregator.swift

@@ -33,6 +33,7 @@ public class MaxValueAggregator<T: SignedNumeric & Comparable>: Aggregator<T>  {
         lock.withLockVoid {
             super.checkpoint()
             self.pointCheck = self.value
+            self.value = 0
         }
     }
 

Tests/ExportersTests/OpenTelemetryProtocol/OtlpMetricExporterTests.swift

@@ -37,9 +37,31 @@ class OtlpMetricExproterTests: XCTestCase {
         exporter.shutdown()
     }
 
+    func testGaugeExport() {
+        let metric = generateGaugeMetric()
+        let exporter = OtelpMetricExporter(channel: channel)
+
+        let result = exporter.export(metrics: [metric]) { () -> Bool in
+            false
+        }
+        XCTAssertEqual(result, MetricExporterResultCode.success)
+
+        XCTAssertEqual(fakeCollector.receivedMetrics.count, 1)
+        let otlpMetric = fakeCollector.receivedMetrics[0].instrumentationLibraryMetrics[0].metrics[0]
+        XCTAssertEqual(metric.name, otlpMetric.name)
+        XCTAssertEqual(otlpMetric.intGauge.dataPoints.count, 1)
+        let dataPoint = otlpMetric.intGauge.dataPoints[0]
+        let sum = metric.data[0] as! SumData<Int>
+        XCTAssertEqual(sum.timestamp.timeIntervalSince1970.toNanoseconds, dataPoint.timeUnixNano)
+        XCTAssertEqual(sum.startTimestamp.timeIntervalSince1970.toNanoseconds, dataPoint.startTimeUnixNano)
+        XCTAssertEqual(sum.sum, Int(dataPoint.value))
+
+    }
+
     func testExportMultipleMetrics() {
         var metrics = [Metric]()
         for _ in 0 ..< 10 {
+
             metrics.append(generateSumMetric())
         }
         let exporter = OtelpMetricExporter(channel: channel)
@@ -98,6 +120,14 @@ class OtlpMetricExproterTests: XCTestCase {
         metric.data.append(data)
         return metric
     }
+
+    func generateGaugeMetric() -> Metric {
+        let library = InstrumentationLibraryInfo(name: "lib", version: "semver:0.0.0")
+        var metric = Metric(namespace: "namespace", name: "MyGauge", desc: "description", type: .intGauge, resource: Resource(), instrumentationLibraryInfo: library)
+        let data = SumData(startTimestamp: Date(), timestamp: Date(), labels: ["hello": "world"], sum: 100)
+        metric.data.append(data)
+        return metric
+    }
 }
 
 class FakeMetricCollector: Opentelemetry_Proto_Collector_Metrics_V1_MetricsServiceProvider {

Tests/OpenTelemetrySdkTests/Metrics/Aggregators/MaxValueAggregatorTests.swift

@@ -0,0 +1,61 @@
+// Copyright 2021, 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.
+//
+
+@testable import OpenTelemetrySdk
+import XCTest
+
+final class MaxValueAggregatorTests : XCTestCase {
+    public func testAsyncSafety() {
+        let agg = MaxValueAggregator<Int>()
+        var sum = agg.toMetricData() as! SumData<Int>
+
+        XCTAssertEqual(sum.sum, 0)
+
+        DispatchQueue.concurrentPerform(iterations: 10) { _ in
+            for i in 0 ..< 10000 {
+                agg.update(value: i)
+            }
+        }
+
+        agg.update(value: 10001)
+
+        agg.checkpoint()
+        sum = agg.toMetricData() as! SumData<Int>
+
+        XCTAssertEqual(sum.sum, 10001)
+    }
+
+    public func testMaxAggPeriod() {
+        let agg = MaxValueAggregator<Int>()
+        var sum = agg.toMetricData() as! SumData<Int>
+
+        XCTAssertEqual(sum.sum, 0)
+
+        agg.update(value: 100)
+        agg.checkpoint()
+
+        sum = agg.toMetricData() as! SumData<Int>
+
+        XCTAssertEqual(sum.sum, 100)
+
+        agg.update(value: 88)
+        agg.checkpoint()
+
+        sum = agg.toMetricData() as! SumData<Int>
+
+        XCTAssertEqual(sum.sum, 88)
+
+    }
+}