test: add unit tests for TracedUnaryCallable extraction

Author: blakeli0

gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedUnaryCallable.java

@@ -37,6 +37,7 @@
 import com.google.api.gax.rpc.ResourceNameExtractor;
 import com.google.api.gax.rpc.UnaryCallable;
 import com.google.api.gax.tracing.ApiTracerFactory.OperationType;
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Strings;
 import com.google.common.util.concurrent.MoreExecutors;
 import javax.annotation.Nullable;
@@ -96,13 +97,7 @@ public TracedUnaryCallable(
   public ApiFuture<ResponseT> futureCall(RequestT request, ApiCallContext context) {
     ApiTracer tracer;
     if (apiTracerContext != null) {
-      ApiTracerContext finalContext = apiTracerContext;
-      // Extract the resource name early
-      String resourceName =
-          resourceNameExtractor != null ? resourceNameExtractor.extract(request) : null;
-      if (!Strings.isNullOrEmpty(resourceName)) {
-        finalContext = finalContext.toBuilder().setDestinationResourceId(resourceName).build();
-      }
+      ApiTracerContext finalContext = extractResourceNameToApiTracerContext(request);
       tracer = tracerFactory.newTracer(context.getTracer(), finalContext);
     } else {
       tracer = tracerFactory.newTracer(context.getTracer(), spanName, OperationType.Unary);
@@ -120,4 +115,16 @@ public ApiFuture<ResponseT> futureCall(RequestT request, ApiCallContext context)
       throw e;
     }
   }
+
+  @VisibleForTesting
+  ApiTracerContext extractResourceNameToApiTracerContext(RequestT request) {
+    ApiTracerContext finalContext = apiTracerContext;
+    // Extract the resource name early
+    String resourceName =
+        resourceNameExtractor != null ? resourceNameExtractor.extract(request) : null;
+    if (!Strings.isNullOrEmpty(resourceName)) {
+      finalContext = finalContext.toBuilder().setDestinationResourceId(resourceName).build();
+    }
+    return finalContext;
+  }
 }

gax-java/gax/src/test/java/com/google/api/gax/tracing/TracedUnaryCallableTest.java

@@ -206,4 +206,29 @@ void testResourceNameExtractorUsed() {
     assertThat(contextCaptor.getValue().destinationResourceId())
         .isEqualTo("extracted-resource-name");
   }
+
+  @Test
+  void testExtractResourceNameToApiTracerContext_nullExtractor() {
+    tracedUnaryCallable = new TracedUnaryCallable<>(innerCallable, tracerFactory, TRACER_CONTEXT);
+    ApiTracerContext context = tracedUnaryCallable.extractResourceNameToApiTracerContext("request");
+    assertThat(context).isEqualTo(TRACER_CONTEXT);
+  }
+
+  @Test
+  void testExtractResourceNameToApiTracerContext_extractorReturnsNull() {
+    tracedUnaryCallable =
+        new TracedUnaryCallable<>(innerCallable, tracerFactory, TRACER_CONTEXT, request -> null);
+    ApiTracerContext context = tracedUnaryCallable.extractResourceNameToApiTracerContext("request");
+    assertThat(context).isEqualTo(TRACER_CONTEXT);
+  }
+
+  @Test
+  void testExtractResourceNameToApiTracerContext_extractorReturnsResourceId() {
+    tracedUnaryCallable =
+        new TracedUnaryCallable<>(
+            innerCallable, tracerFactory, TRACER_CONTEXT, request -> "extracted-id");
+    ApiTracerContext context = tracedUnaryCallable.extractResourceNameToApiTracerContext("request");
+    assertThat(context).isNotSameInstanceAs(TRACER_CONTEXT);
+    assertThat(context.destinationResourceId()).isEqualTo("extracted-id");
+  }
 }