diff --git a/utilities/external-interface/CMakeLists.txt b/utilities/external-interface/CMakeLists.txt
index d37bb6c4d5..779332e6aa 100644
--- a/utilities/external-interface/CMakeLists.txt
+++ b/utilities/external-interface/CMakeLists.txt
@@ -20,3 +20,10 @@ target_link_libraries(external_interface
 )
 
 target_set_warning_flags(external_interface)
+
+foreach(DRIVER IN ITEMS "ccsd" "nevpt2")
+    add_test(
+        NAME "sequant/external_interface/${DRIVER}"
+        COMMAND external_interface --driver "${CMAKE_CURRENT_LIST_DIR}/examples/${DRIVER}.json"
+    )
+endforeach()
diff --git a/utilities/external-interface/external_interface.cpp b/utilities/external-interface/external_interface.cpp
index 0ca5a4f508..cabc8c686c 100644
--- a/utilities/external-interface/external_interface.cpp
+++ b/utilities/external-interface/external_interface.cpp
@@ -422,8 +422,15 @@ void generalSetup() {
 
 int main(int argc, char **argv) {
   set_locale();
-  set_default_context({.index_space_registry = IndexSpaceRegistry(),
-                       .vacuum = Vacuum::SingleProduct});
+  Context ctx({.index_space_registry = IndexSpaceRegistry(),
+               .vacuum = Vacuum::SingleProduct});
+  // TODO: This only hides a bug/issue in the processing code where SeQuant
+  // assumes that it is okay to freely rename external indices while
+  // canonicalizing an expression. However, this breaks down as soon as those
+  // indices are tracked externally (e.g. ResultExpr) as those won't get updated
+  // to use the new names.
+  ctx.set(CanonicalizeOptions{.method = CanonicalizationMethod::Complete});
+  set_default_context(ctx);
   generalSetup();
 
   CLI::App app(