Add tests for OTTraceCorrelation

dd-trace-ot/src/main/java/datadog/opentracing/OTTraceCorrelation.java

@@ -1,17 +1,29 @@
 package datadog.opentracing;
 
+import com.google.common.annotations.VisibleForTesting;
 import datadog.trace.api.CorrelationIdentifier;
 import io.opentracing.Span;
+import io.opentracing.Tracer;
 import io.opentracing.util.GlobalTracer;
 
 public class OTTraceCorrelation implements CorrelationIdentifier.Provider {
   public static final OTTraceCorrelation INSTANCE = new OTTraceCorrelation();
 
-  private OTTraceCorrelation() {}
+  private final Tracer tracer;
+
+  private OTTraceCorrelation() {
+    // GlobalTracer.get() is guaranteed to return a constant so we can keep reference to it
+    this(GlobalTracer.get());
+  }
+
+  @VisibleForTesting
+  OTTraceCorrelation(Tracer tracer) {
+    this.tracer = tracer;
+  }
 
   @Override
   public long getTraceId() {
-    final Span activeSpan = GlobalTracer.get().activeSpan();
+    final Span activeSpan = tracer.activeSpan();
     if (activeSpan instanceof DDSpan) {
       return ((DDSpan) activeSpan).getTraceId();
     }
@@ -20,7 +32,7 @@ public class OTTraceCorrelation implements CorrelationIdentifier.Provider {
 
   @Override
   public long getSpanId() {
-    final Span activeSpan = GlobalTracer.get().activeSpan();
+    final Span activeSpan = tracer.activeSpan();
     if (activeSpan instanceof DDSpan) {
       return ((DDSpan) activeSpan).getSpanId();
     }

dd-trace-ot/src/test/groovy/datadog/opentracing/OTTraceCorrelationTest.groovy

@@ -0,0 +1,47 @@
+package datadog.opentracing
+
+import datadog.trace.common.writer.ListWriter
+import spock.lang.Shared
+import spock.lang.Specification
+
+class OTTraceCorrelationTest extends Specification {
+
+  static final WRITER = new ListWriter()
+
+  @Shared
+  DDTracer tracer = new DDTracer(WRITER)
+  @Shared
+  OTTraceCorrelation traceCorrelation = new OTTraceCorrelation(tracer)
+
+  def scope = tracer.buildSpan("test").startActive(true)
+
+  def cleanup() {
+    scope.close()
+  }
+
+  def "get trace id without trace"() {
+    setup:
+    scope.close()
+
+    expect:
+    0 == traceCorrelation.getTraceId()
+  }
+
+  def "get trace id with trace"() {
+    expect:
+    ((DDSpan) scope.span()).traceId == traceCorrelation.getTraceId()
+  }
+
+  def "get span id without span"() {
+    setup:
+    scope.close()
+
+    expect:
+    0 == traceCorrelation.getSpanId()
+  }
+
+  def "get span id with trace"() {
+    expect:
+    ((DDSpan) scope.span()).spanId == traceCorrelation.getSpanId()
+  }
+}