diff --git a/lib/cretonne/src/write.rs b/lib/cretonne/src/write.rs
index b4276349de..9de3e93d58 100644
--- a/lib/cretonne/src/write.rs
+++ b/lib/cretonne/src/write.rs
@@ -447,9 +447,9 @@ mod tests {
     #[test]
     fn basic() {
         let mut f = Function::new();
-        assert_eq!(f.to_string(), "function %() native {\n}\n");
+        assert_eq!(f.to_string(), "function u0:0() native {\n}\n");
 
-        f.name = ExternalName::new("foo");
+        f.name = ExternalName::testcase("foo");
         assert_eq!(f.to_string(), "function %foo() native {\n}\n");
 
         f.create_stack_slot(StackSlotData::new(StackSlotKind::Local, 4));
diff --git a/lib/frontend/src/frontend.rs b/lib/frontend/src/frontend.rs
index 5127270cbd..432288e4eb 100644
--- a/lib/frontend/src/frontend.rs
+++ b/lib/frontend/src/frontend.rs
@@ -613,7 +613,7 @@ mod tests {
         sig.params.push(AbiParam::new(I32));
 
         let mut il_builder = ILBuilder::<Variable>::new();
-        let mut func = Function::with_name_signature(ExternalName::new("sample_function"), sig);
+        let mut func = Function::with_name_signature(ExternalName::testcase("sample"), sig);
         {
             let mut builder = FunctionBuilder::<Variable>::new(&mut func, &mut il_builder);
 
diff --git a/lib/frontend/src/lib.rs b/lib/frontend/src/lib.rs
index 12b8c8db73..4307023ab9 100644
--- a/lib/frontend/src/lib.rs
+++ b/lib/frontend/src/lib.rs
@@ -62,7 +62,7 @@
 //!     sig.returns.push(AbiParam::new(I32));
 //!     sig.params.push(AbiParam::new(I32));
 //!     let mut il_builder = ILBuilder::<Variable>::new();
-//!     let mut func = Function::with_name_signature(ExternalName::new("sample_function"), sig);
+//!     let mut func = Function::with_name_signature(ExternalName::user(0, 0), sig);
 //!     {
 //!         let mut builder = FunctionBuilder::<Variable>::new(&mut func, &mut il_builder);
 //!
diff --git a/lib/wasm/src/func_translator.rs b/lib/wasm/src/func_translator.rs
index b5407decd9..f68996d9b6 100644
--- a/lib/wasm/src/func_translator.rs
+++ b/lib/wasm/src/func_translator.rs
@@ -252,7 +252,7 @@ mod tests {
         let runtime = DummyEnvironment::default();
         let mut ctx = Context::new();
 
-        ctx.func.name = ir::ExternalName::new("small1");
+        ctx.func.name = ir::ExternalName::testcase("small1");
         ctx.func.signature.params.push(ir::AbiParam::new(I32));
         ctx.func.signature.returns.push(ir::AbiParam::new(I32));
 
@@ -283,7 +283,7 @@ mod tests {
         let runtime = DummyEnvironment::default();
         let mut ctx = Context::new();
 
-        ctx.func.name = ir::ExternalName::new("small2");
+        ctx.func.name = ir::ExternalName::testcase("small2");
         ctx.func.signature.params.push(ir::AbiParam::new(I32));
         ctx.func.signature.returns.push(ir::AbiParam::new(I32));
 
@@ -323,7 +323,7 @@ mod tests {
         let runtime = DummyEnvironment::default();
         let mut ctx = Context::new();
 
-        ctx.func.name = ir::ExternalName::new("infloop");
+        ctx.func.name = ir::ExternalName::testcase("infloop");
         ctx.func.signature.returns.push(ir::AbiParam::new(I32));
 
         trans