diff --git a/test/harness/wasm-constants.js b/test/harness/wasm-constants.js
index 68c36ef1fd..9e06985990 100644
--- a/test/harness/wasm-constants.js
+++ b/test/harness/wasm-constants.js
@@ -87,7 +87,6 @@ let kWasmI32 = 0x7f;
 let kWasmI64 = 0x7e;
 let kWasmF32 = 0x7d;
 let kWasmF64 = 0x7c;
-let kWasmS128 = 0x7b;
 
 let kExternalFunction = 0;
 let kExternalTable = 1;
@@ -118,7 +117,6 @@ let kSig_v_l = makeSig([kWasmI64], []);
 let kSig_v_d = makeSig([kWasmF64], []);
 let kSig_v_dd = makeSig([kWasmF64, kWasmF64], []);
 let kSig_v_ddi = makeSig([kWasmF64, kWasmF64, kWasmI32], []);
-let kSig_s_v = makeSig([], [kWasmS128]);
 
 function makeSig(params, results) {
   return {params: params, results: results};
diff --git a/test/harness/wasm-module-builder.js b/test/harness/wasm-module-builder.js
index d9948eb1a4..f73794bacc 100644
--- a/test/harness/wasm-module-builder.js
+++ b/test/harness/wasm-module-builder.js
@@ -74,9 +74,7 @@ class Binary extends Array {
     // Emit section length.
     this.emit_u32v(section.length);
     // Copy the temporary buffer.
-    for (const sectionByte of section) {
-      this.push(sectionByte);
-    }
+    this.push(...section);
   }
 }
 
@@ -88,6 +86,15 @@ class WasmFunctionBuilder {
     this.body = [];
   }
 
+  numLocalNames() {
+    if (this.local_names === undefined) return 0;
+    let num_local_names = 0;
+    for (let loc_name of this.local_names) {
+      if (loc_name !== undefined) ++num_local_names;
+    }
+    return num_local_names;
+  }
+
   exportAs(name) {
     this.module.addExport(name, this.index);
     return this;
@@ -101,7 +108,7 @@ class WasmFunctionBuilder {
   addBody(body) {
     for (let b of body) {
       if (typeof b !== 'number' || (b & (~0xFF)) !== 0 )
-        throw new Error('invalid body (entries have to be 8 bit numbers): ' + body);
+        throw new Error('invalid body (entries must be 8 bit numbers): ' + body);
     }
     this.body = body.slice();
     // Automatically add the end for the function block to the body.
@@ -109,8 +116,14 @@ class WasmFunctionBuilder {
     return this;
   }
 
-  addLocals(locals) {
+  addBodyWithEnd(body) {
+    this.body = body;
+    return this;
+  }
+
+  addLocals(locals, names) {
     this.locals = locals;
+    this.local_names = names;
     return this;
   }
 
@@ -274,6 +287,11 @@ class WasmModuleBuilder {
     return this;
   }
 
+  setName(name) {
+    this.name = name;
+    return this;
+  }
+
   toArray(debug = false) {
     let binary = new Binary;
     let wasm = this;
@@ -333,16 +351,11 @@ class WasmModuleBuilder {
     }
 
     // Add functions declarations
-    let num_function_names = 0;
-    let names = false;
     if (wasm.functions.length > 0) {
       if (debug) print("emitting function decls @ " + binary.length);
       binary.emit_section(kFunctionSectionCode, section => {
         section.emit_u32v(wasm.functions.length);
         for (let func of wasm.functions) {
-          if (func.name !== undefined) {
-            ++num_function_names;
-          }
           section.emit_u32v(func.type_index);
         }
       });
@@ -543,19 +556,51 @@ class WasmModuleBuilder {
       binary.emit_bytes(exp);
     }
 
-    // Add function names.
-    if (num_function_names > 0) {
+    // Add names.
+    let num_function_names = 0;
+    let num_functions_with_local_names = 0;
+    for (let func of wasm.functions) {
+      if (func.name !== undefined) ++num_function_names;
+      if (func.numLocalNames() > 0) ++num_functions_with_local_names;
+    }
+    if (num_function_names > 0 || num_functions_with_local_names > 0 ||
+        wasm.name !== undefined) {
       if (debug) print('emitting names @ ' + binary.length);
       binary.emit_section(kUnknownSectionCode, section => {
         section.emit_string('name');
-        section.emit_section(kFunctionNamesCode, name_section => {
-          name_section.emit_u32v(num_function_names);
-          for (let func of wasm.functions) {
-            if (func.name === undefined) continue;
-            name_section.emit_u32v(func.index);
-            name_section.emit_string(func.name);
-          }
-        });
+        // Emit module name.
+        if (wasm.name !== undefined) {
+          section.emit_section(kModuleNameCode, name_section => {
+            name_section.emit_string(wasm.name);
+          });
+        }
+        // Emit function names.
+        if (num_function_names > 0) {
+          section.emit_section(kFunctionNamesCode, name_section => {
+            name_section.emit_u32v(num_function_names);
+            for (let func of wasm.functions) {
+              if (func.name === undefined) continue;
+              name_section.emit_u32v(func.index);
+              name_section.emit_string(func.name);
+            }
+          });
+        }
+        // Emit local names.
+        if (num_functions_with_local_names > 0) {
+          section.emit_section(kLocalNamesCode, name_section => {
+            name_section.emit_u32v(num_functions_with_local_names);
+            for (let func of wasm.functions) {
+              if (func.numLocalNames() == 0) continue;
+              name_section.emit_u32v(func.index);
+              name_section.emit_u32v(func.numLocalNames());
+              for (let i = 0; i < func.local_names.length; ++i) {
+                if (func.local_names[i] === undefined) continue;
+                name_section.emit_u32v(i);
+                name_section.emit_string(func.local_names[i]);
+              }
+            }
+          });
+        }
       });
     }
 
@@ -579,4 +624,8 @@ class WasmModuleBuilder {
     let instance = new WebAssembly.Instance(module, ffi);
     return instance;
   }
+
+  toModule(debug = false) {
+    return new WebAssembly.Module(this.toBuffer(debug));
+  }
 }