fix: Fix a bug breaking all span tags

Somehow I brain-farted and mixed up if and unless, and then also didn't
run the test suite which would've told me that this isn't working.

Also adding more test coverage in this, just to be safe.

lib/degica_datadog/tracing.rb

@@ -111,14 +111,14 @@ def error!(e)
 
       # Returns the current span.
       def current_span
-        Datadog::Tracing.active_span unless Config.enabled?
+        Datadog::Tracing.active_span if Config.enabled?
       end
 
       # Returns the current root span. Root here meaning within the service, not necessarily the
       # actual trace root span if that is from a different service.
       def root_span
         # forgive me my friends
-        Datadog::Tracing.active_trace.instance_variable_get(:@root_span) unless Config.enabled?
+        Datadog::Tracing.active_trace.instance_variable_get(:@root_span) if Config.enabled?
       end
 
       # Please don't use this. It's just a temporary thing until we can get the

spec/tracing_spec.rb

@@ -13,6 +13,38 @@
     end
   end
 
+  describe ".current_span" do
+    it "does nothing when disabled" do
+      allow(DegicaDatadog::Config).to receive(:enabled?).and_return(false)
+      described_class.span!("test") do
+        expect(described_class.current_span).to be_nil
+      end
+    end
+
+    it "returns the current span" do
+      allow(DegicaDatadog::Config).to receive(:enabled?).and_return(true)
+      described_class.span!("test") do
+        expect(described_class.current_span).to_not be_nil
+      end
+    end
+  end
+
+  describe ".root_span" do
+    it "does nothing when disabled" do
+      allow(DegicaDatadog::Config).to receive(:enabled?).and_return(false)
+      described_class.span!("test") do
+        expect(described_class.root_span).to be_nil
+      end
+    end
+
+    it "returns the current span" do
+      allow(DegicaDatadog::Config).to receive(:enabled?).and_return(true)
+      described_class.span!("test") do
+        expect(described_class.root_span).to_not be_nil
+      end
+    end
+  end
+
   describe ".span!" do
     it "starts a new span" do
       expect { described_class.span!("test") }.to change { Datadog::Tracing.active_span }.from(nil)