new tests

project.cpp

@@ -90,5 +90,15 @@ extern "C" Configuration CrafterBuildProject(std::span<const std::string_view> a
         crafterBuildLib->linkFlags.push_back("-lws2_32");
     }
 
+    // Self-tests link the local crafter-build library and exercise it in
+    // process. The harness (whichever crafter-build invokes `test`) compiles
+    // these against the *installed* share/crafter-build .cppm files, then
+    // links each test exe against crafterBuildLib built from the local
+    // sources — so the code under test is whatever's in this checkout.
+    // Mirrors how downstream consumers link their own libraries into tests.
+    if (cfg.target == "x86_64-pc-linux-gnu") {
+        cfg.AddTest("HelloWorld").Dependencies({ crafterBuildLib.get() });
+    }
+
     return cfg;
 }