Improve grpc metadata overwrite test

instrumentation/grpc-1.6/library/src/test/java/io/opentelemetry/instrumentation/grpc/v1_6/MetadataSetterTest.java

@@ -5,28 +5,63 @@
 
 package io.opentelemetry.instrumentation.grpc.v1_6;
 
-import static org.junit.Assert.assertTrue;
+import static org.assertj.core.api.Assertions.assertThat;
 
 import io.grpc.Metadata;
+import io.opentelemetry.api.trace.Span;
+import io.opentelemetry.api.trace.SpanContext;
+import io.opentelemetry.api.trace.SpanId;
+import io.opentelemetry.api.trace.TraceFlags;
+import io.opentelemetry.api.trace.TraceId;
+import io.opentelemetry.api.trace.TraceState;
+import io.opentelemetry.api.trace.propagation.W3CTraceContextPropagator;
 import io.opentelemetry.context.Context;
-import io.opentelemetry.instrumentation.grpc.v1_6.propagator.GrpcPropagator;
+import io.opentelemetry.context.propagation.TextMapGetter;
+import io.opentelemetry.context.propagation.TextMapPropagator;
+import javax.annotation.Nullable;
 import org.junit.jupiter.api.Test;
 
 class MetadataSetterTest {
 
-    @Test
-    void checkThatIterableSizeEqualsOne() {
-        GrpcPropagator testGrpcPropagator = new GrpcPropagator();
-        Metadata metadata = new Metadata();
-        testGrpcPropagator.inject(Context.current(), metadata, MetadataSetter.INSTANCE);
-
-        int size = 0;
-        for (String s :
-                metadata.getAll(Metadata.Key.of(testGrpcPropagator.fields().get(0), Metadata.ASCII_STRING_MARSHALLER))) {
-            if (s != null) {
-                size++;
-            }
-        }
-        assertTrue(size == 1);
+  @Test
+  void overwriteTracingHeader() {
+    Metadata metadata = new Metadata();
+    TextMapPropagator propagator = W3CTraceContextPropagator.getInstance();
+    for (int i = 1; i <= 2; i++) {
+      Context context =
+          Context.root()
+              .with(
+                  Span.wrap(
+                      SpanContext.create(
+                          TraceId.fromLongs(0, i),
+                          SpanId.fromLong(i),
+                          TraceFlags.getDefault(),
+                          TraceState.getDefault())));
+      propagator.inject(context, metadata, MetadataSetter.INSTANCE);
     }
+
+    assertThat(metadata.getAll(Metadata.Key.of("traceparent", Metadata.ASCII_STRING_MARSHALLER)))
+        .hasSize(1);
+
+    Context context =
+        propagator.extract(
+            Context.root(),
+            metadata,
+            new TextMapGetter<Metadata>() {
+              @Override
+              public Iterable<String> keys(Metadata metadata) {
+                return metadata.keys();
+              }
+
+              @Nullable
+              @Override
+              public String get(@Nullable Metadata metadata, String key) {
+                return metadata.get(Metadata.Key.of(key, Metadata.ASCII_STRING_MARSHALLER));
+              }
+            });
+
+    SpanContext spanContext = Span.fromContext(context).getSpanContext();
+    assertThat(spanContext.getTraceId()).isEqualTo(TraceId.fromLongs(0, 2));
+    assertThat(spanContext.getSpanId()).isEqualTo(SpanId.fromLong(2));
+  }
 }