Add explicit pipeline configuration imports

internal/config/notarius_test.go

@@ -117,8 +117,13 @@ func TestNotariusStrictYAML(t *testing.T) {
 			if err := os.WriteFile(path, []byte(testPipelineBaseYAML+"\n"+tt.yaml), 0o644); err != nil {
 				t.Fatalf("write pipeline: %v", err)
 			}
-			if _, err := LoadPipeline(path); err == nil || !strings.Contains(err.Error(), "strict decode failed") {
-				t.Fatalf("LoadPipeline() error = %v, want strict decode failure", err)
+			_, err := LoadPipeline(path)
+			want := "strict decode failed"
+			if tt.name == "duplicate reference selector" {
+				want = "duplicate YAML key"
+			}
+			if err == nil || !strings.Contains(err.Error(), want) {
+				t.Fatalf("LoadPipeline() error = %v, want containing %q", err, want)
 			}
 		})
 	}