Re-organize unit tests somewhat

Author: zacharycmontoya

tracer/test/Datadog.Trace.Tests/SpanLinksTests.cs

@@ -27,22 +27,6 @@ public SpanLinksTests()
             _tracer = new Tracer(settings, writerMock.Object, samplerMock.Object, scopeManager: null, statsd: null);
         }
 
-        [Fact]
-        public void AddLink_AfterSpanFinished_IsNoOp()
-        {
-            var parentScope = (Scope)_tracer.StartActive("Parent");
-            var childScope = (Scope)_tracer.StartActive("Child");
-
-            var parentSpan = parentScope.Span;
-            var childSpan = childScope.Span;
-            var spanLink = new SpanLink(parentSpan.Context);
-
-            childSpan.Finish();
-
-            childSpan.AddLink(spanLink);
-            childSpan.SpanLinks.Should().BeNullOrEmpty();
-        }
-
         [Fact]
         public void AddAttribute_BeforeSpanFinished_IsSuccessful()
         {

tracer/test/Datadog.Trace.Tests/SpanTests.cs

@@ -69,6 +69,38 @@ public void SetPeerServiceTag_CallsRemapper()
             span.GetTag(Tags.PeerServiceRemappedFrom).Should().Be("a-peer-service");
         }
 
+        [Fact]
+        public void AddLink_BeforeSpanFinished_IsSuccessful()
+        {
+            var parentScope = (Scope)_tracer.StartActive("Parent");
+            var childScope = (Scope)_tracer.StartActive("Child");
+
+            var parentSpan = parentScope.Span;
+            var childSpan = childScope.Span;
+            var spanLink = new SpanLink(parentSpan.Context);
+
+            childSpan.AddLink(spanLink);
+            childSpan.Finish();
+
+            childSpan.SpanLinks.Should().ContainSingle();
+        }
+
+        [Fact]
+        public void AddLink_AfterSpanFinished_IsNoOp()
+        {
+            var parentScope = (Scope)_tracer.StartActive("Parent");
+            var childScope = (Scope)_tracer.StartActive("Child");
+
+            var parentSpan = parentScope.Span;
+            var childSpan = childScope.Span;
+            var spanLink = new SpanLink(parentSpan.Context);
+
+            childSpan.Finish();
+            childSpan.AddLink(spanLink);
+
+            childSpan.SpanLinks.Should().BeNullOrEmpty();
+        }
+
         [Fact]
         public void Finish_StartTimeInThePastWithNoEndTime_DurationProperlyComputed()
         {