make test session name tests more stable

spec/datadog/ci/test_visibility/component_spec.rb

@@ -436,7 +436,13 @@
         end
 
         context "without logical test session name set" do
+          before do
+            allow_any_instance_of(Datadog::CI::TestSession).to receive(:ci_job_name).and_return(ci_job_name)
+          end
+
           context "without CI job name available" do
+            let(:ci_job_name) { nil }
+
             it "uses the test command" do
               subject
 
@@ -447,10 +453,6 @@
           context "with CI job name available" do
             let(:ci_job_name) { "my-ci-job" }
 
-            before do
-              allow_any_instance_of(Datadog::CI::TestSession).to receive(:ci_job_name).and_return(ci_job_name)
-            end
-
             it "uses the CI job name and test command" do
               subject