diff --git a/opentelemetry-sdk/src/metrics/mod.rs b/opentelemetry-sdk/src/metrics/mod.rs
index c74e71bcd5..13e9d35cbc 100644
--- a/opentelemetry-sdk/src/metrics/mod.rs
+++ b/opentelemetry-sdk/src/metrics/mod.rs
@@ -57,3 +57,103 @@ pub use meter_provider::*;
 pub use periodic_reader::*;
 pub use pipeline::Pipeline;
 pub use view::*;
+
+#[cfg(all(test, feature = "testing"))]
+mod tests {
+    use super::*;
+    use crate::{runtime, testing::metrics::InMemoryMetricsExporter};
+    use opentelemetry::{
+        metrics::{MeterProvider as _, Unit},
+        KeyValue,
+    };
+
+    // "multi_thread" tokio flavor must be used else flush won't
+    // be able to make progress!
+    #[tokio::test(flavor = "multi_thread", worker_threads = 1)]
+    async fn counter_aggregation() {
+        // Run this test with stdout enabled to see output.
+        // cargo test counter --features=metrics,testing -- --nocapture
+
+        // Arrange
+        let exporter = InMemoryMetricsExporter::default();
+        let reader = PeriodicReader::builder(exporter.clone(), runtime::Tokio).build();
+        let meter_provider = SdkMeterProvider::builder().with_reader(reader).build();
+
+        // Act
+        let meter = meter_provider.meter("test");
+        let counter = meter
+            .u64_counter("my_counter")
+            .with_unit(Unit::new("my_unit"))
+            .init();
+        counter.add(1, &[KeyValue::new("key1", "value1")]);
+        counter.add(1, &[KeyValue::new("key1", "value1")]);
+        counter.add(1, &[KeyValue::new("key1", "value1")]);
+        counter.add(1, &[KeyValue::new("key1", "value1")]);
+        counter.add(1, &[KeyValue::new("key1", "value1")]);
+
+        counter.add(1, &[KeyValue::new("key1", "value2")]);
+        counter.add(1, &[KeyValue::new("key1", "value2")]);
+        counter.add(1, &[KeyValue::new("key1", "value2")]);
+
+        meter_provider.force_flush().unwrap();
+
+        // Assert
+        let resource_metrics = exporter
+            .get_finished_metrics()
+            .expect("metrics are expected to be exported.");
+        assert!(!resource_metrics.is_empty());
+        let metric = &resource_metrics[0].scope_metrics[0].metrics[0];
+        assert_eq!(metric.name, "my_counter");
+        assert_eq!(metric.unit.as_str(), "my_unit");
+        let sum = metric
+            .data
+            .as_any()
+            .downcast_ref::<data::Sum<u64>>()
+            .expect("Sum aggregation expected for Counter instruments by default");
+
+        // Expecting 2 time-series.
+        assert_eq!(sum.data_points.len(), 2);
+        assert!(sum.is_monotonic, "Counter should produce monotonic.");
+        assert_eq!(
+            sum.temporality,
+            data::Temporality::Cumulative,
+            "Should produce cumulative by default."
+        );
+
+        // find and validate key1=value1 datapoint
+        let mut data_point1 = None;
+        for datapoint in &sum.data_points {
+            if datapoint
+                .attributes
+                .iter()
+                .any(|(k, v)| k.as_str() == "key1" && v.as_str() == "value1")
+            {
+                data_point1 = Some(datapoint);
+            }
+        }
+        assert_eq!(
+            data_point1
+                .expect("datapoint with key1=value1 expected")
+                .value,
+            5
+        );
+
+        // find and validate key1=value2 datapoint
+        let mut data_point1 = None;
+        for datapoint in &sum.data_points {
+            if datapoint
+                .attributes
+                .iter()
+                .any(|(k, v)| k.as_str() == "key1" && v.as_str() == "value2")
+            {
+                data_point1 = Some(datapoint);
+            }
+        }
+        assert_eq!(
+            data_point1
+                .expect("datapoint with key1=value2 expected")
+                .value,
+            3
+        );
+    }
+}