From b6a122940830d0f438edb24e000ee9447e8419fe Mon Sep 17 00:00:00 2001
From: Hermes Agent <hermes@localhost>
Date: Wed, 12 Aug 2026 05:36:28 +0000
Subject: Test pre-existing artifact build guard

---
 tests/build.rs | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/tests/build.rs b/tests/build.rs
index d278bce..6613cc7 100644
--- a/tests/build.rs
+++ b/tests/build.rs
@@ -90,6 +90,28 @@ fn refuses_to_reuse_an_existing_workspace() {
     assert!(installer.requests.borrow().is_empty());
 }
 
+#[test]
+fn rejects_an_existing_artifact_before_creating_the_workspace_or_installing() {
+    let fixture = tempdir().expect("fixture directory");
+    let spec = ImageSpec::load(std::path::Path::new("profiles/alt-controller.toml"))
+        .expect("load controller spec");
+    let plan = BuildPlan::compile(spec).expect("compile build plan");
+    let installer = FixtureInstaller::default();
+    let mut executor = BuildExecutor::new(&installer, FixtureInitramfsBuilder);
+    let workspace = fixture.path().join("work");
+    let artifact = fixture.path().join("existing.tar");
+    fs::write(&artifact, "do not replace").expect("write pre-existing artifact");
+
+    let error = executor
+        .execute(&plan, &workspace, "profiles/apt.conf", &artifact)
+        .expect_err("pre-existing artifact must be rejected");
+
+    assert!(error.to_string().contains("output artifact already exists"));
+    assert_eq!(fs::read_to_string(&artifact).expect("read artifact"), "do not replace");
+    assert!(!workspace.exists());
+    assert!(installer.requests.borrow().is_empty());
+}
+
 #[test]
 fn rejects_a_missing_apt_configuration_before_creating_the_workspace() {
     let fixture = tempdir().expect("fixture directory");
-- 
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