diff --git a/src/main_wpt.zig b/src/main_wpt.zig
index cc3e013d..3f2396ee 100644
--- a/src/main_wpt.zig
+++ b/src/main_wpt.zig
@@ -70,7 +70,13 @@ pub fn main() !void {
         defer _ = test_arena.reset(.{ .retain_capacity = {} });
 
         var err_out: ?[]const u8 = null;
-        const result = run(test_arena.allocator(), test_file, &loader, &err_out) catch |err| blk: {
+        const result = run(
+            test_arena.allocator(),
+            &platform,
+            test_file,
+            &loader,
+            &err_out,
+        ) catch |err| blk: {
             if (err_out == null) {
                 err_out = @errorName(err);
             }
@@ -89,7 +95,13 @@ pub fn main() !void {
     try writer.finalize();
 }
 
-fn run(arena: Allocator, test_file: []const u8, loader: *FileLoader, err_out: *?[]const u8) !?[]const u8 {
+fn run(
+    arena: Allocator,
+    platform: *const Platform,
+    test_file: []const u8,
+    loader: *FileLoader,
+    err_out: *?[]const u8,
+) !?[]const u8 {
     // document
     const html = blk: {
         const full_path = try std.fs.path.join(arena, &.{ WPT_DIR, test_file });
@@ -110,6 +122,7 @@ fn run(arena: Allocator, test_file: []const u8, loader: *FileLoader, err_out: *?
     var runner = try @import("testing.zig").jsRunner(arena, .{
         .url = "http://127.0.0.1",
         .html = html,
+        .platform = platform,
     });
     defer runner.deinit();
 
diff --git a/src/testing.zig b/src/testing.zig
index f5e9c20b..f05f9023 100644
--- a/src/testing.zig
+++ b/src/testing.zig
@@ -19,6 +19,8 @@
 const std = @import("std");
 const Allocator = std.mem.Allocator;
 
+const Platform = @import("runtime/js.zig").Platform;
+
 pub const allocator = std.testing.allocator;
 pub const expectError = std.testing.expectError;
 pub const expect = std.testing.expect;
@@ -383,6 +385,7 @@ pub const JsRunner = struct {
         var app = try App.init(alloc, .{
             .run_mode = .serve,
             .tls_verify_host = false,
+            .platform = opts.platform,
         });
         errdefer app.deinit();
 
@@ -474,6 +477,7 @@ pub const JsRunner = struct {
 };
 
 const RunnerOpts = struct {
+    platform: ?*const Platform = null,
     url: []const u8 = "https://lightpanda.io/opensource-browser/",
     html: []const u8 =
         \\ <div id="content">