• download the server jar from here https://piston-data.mojang.com/v1/objects/e003d151668a0eff64c1191972707655e341f8f5/server.jar
• create a datapack with a test that references a structure that doesnt exist (or download my example) and place it in a testpacks folder next to the jar. (need to unzip it to avoid running into MC-279522)
• run "java -DbundlerMainClass="net.minecraft.gametest.Main" -jar server.jar --packs testpacks --report=test.xml"
• observe that the output only shows the one inbuild test, not the failure of the custom one

code analysis

GameTestInfo#placeStructure fails the test if the structure can't be spawned. however failing the test means it will never start ticking and as such

this.listeners.forEach(listener -> listener.testFailed(this, runner))

is never called so the failure can't be reported in the report.xml