Adds unit tests

1 files changed, 9 insertions, 2 deletions

diff --git a/lib/trace/metric/trace.ts b/lib/trace/metric/trace.ts
index b28d828..396bd9c 100644
--- a/lib/trace/metric/trace.ts
+++ b/lib/trace/metric/trace.ts
@@ -16,9 +16,16 @@ export class MetricsTrace implements ITrace<MetricsTraceSupplier> {
     public traceScope(trace: MetricsTraceSupplier): MetricsTrace {
         const now = Date.now();
         const metricsToTrace = (Array.isArray(trace) ? trace : [trace]).filter(isIMetric);
-        const initialTraces = new Map(metricsToTrace.map((metric) => [metric.name, now]));
 
-        return new MetricsTrace(this.metricConsumer, initialTraces, this.completedTraces);
+        // Inherit existing active traces across scopes.
+        const nextActiveTraces = new Map(this.activeTraces);
+        for (const metric of metricsToTrace) {
+            if (!nextActiveTraces.has(metric.name)) {
+                nextActiveTraces.set(metric.name, now);
+            }
+        }
+
+        return new MetricsTrace(this.metricConsumer, nextActiveTraces, this.completedTraces);
     }
 
     public trace(metrics: MetricsTraceSupplier): MetricsTrace {