diff --git a/lib/compiler/test_runner.zig b/lib/compiler/test_runner.zig
index 8b60a75399..b6787dfc7c 100644
--- a/lib/compiler/test_runner.zig
+++ b/lib/compiler/test_runner.zig
@@ -120,6 +120,7 @@ fn mainServer() !void {
 
             .run_test => {
                 testing.allocator_instance = .{};
+                testing.io_instance = .init(fba.allocator());
                 log_err_count = 0;
                 const index = try server.receiveBody_u32();
                 const test_fn = builtin.test_functions[index];
@@ -135,6 +136,8 @@ fn mainServer() !void {
                         }
                     },
                 };
+                testing.io_instance.deinit();
+                fba.reset();
                 const leak = testing.allocator_instance.deinit() == .leak;
                 try server.serveTestResults(.{
                     .index = index,
@@ -194,18 +197,14 @@ fn mainTerminal() void {
     });
     const have_tty = std.fs.File.stderr().isTty();
 
-    var async_frame_buffer: []align(builtin.target.stackAlignment()) u8 = undefined;
-    // TODO this is on the next line (using `undefined` above) because otherwise zig incorrectly
-    // ignores the alignment of the slice.
-    async_frame_buffer = &[_]u8{};
-
     var leaks: usize = 0;
     for (test_fn_list, 0..) |test_fn, i| {
         testing.allocator_instance = .{};
+        testing.io_instance = .init(fba.allocator());
         defer {
-            if (testing.allocator_instance.deinit() == .leak) {
-                leaks += 1;
-            }
+            if (testing.allocator_instance.deinit() == .leak) leaks += 1;
+            testing.io_instance.deinit();
+            fba.reset();
         }
         testing.log_level = .warn;
 
diff --git a/lib/std/Io/test.zig b/lib/std/Io/test.zig
index bf14f0c24c..023cff1b06 100644
--- a/lib/std/Io/test.zig
+++ b/lib/std/Io/test.zig
@@ -1,5 +1,5 @@
 const std = @import("std");
-const io = std.io;
+const Io = std.Io;
 const DefaultPrng = std.Random.DefaultPrng;
 const expect = std.testing.expect;
 const expectEqual = std.testing.expectEqual;
@@ -24,7 +24,7 @@ test "write a file, read it, then delete it" {
         var file = try tmp.dir.createFile(tmp_file_name, .{});
         defer file.close();
 
-        var buf_stream = io.bufferedWriter(file.deprecatedWriter());
+        var buf_stream = Io.bufferedWriter(file.deprecatedWriter());
         const st = buf_stream.writer();
         try st.print("begin", .{});
         try st.writeAll(data[0..]);
@@ -45,7 +45,7 @@ test "write a file, read it, then delete it" {
         const expected_file_size: u64 = "begin".len + data.len + "end".len;
         try expectEqual(expected_file_size, file_size);
 
-        var buf_stream = io.bufferedReader(file.deprecatedReader());
+        var buf_stream = Io.bufferedReader(file.deprecatedReader());
         const st = buf_stream.reader();
         const contents = try st.readAllAlloc(std.testing.allocator, 2 * 1024);
         defer std.testing.allocator.free(contents);
@@ -66,7 +66,7 @@ test "BitStreams with File Stream" {
         var file = try tmp.dir.createFile(tmp_file_name, .{});
         defer file.close();
 
-        var bit_stream = io.bitWriter(native_endian, file.deprecatedWriter());
+        var bit_stream = Io.bitWriter(native_endian, file.deprecatedWriter());
 
         try bit_stream.writeBits(@as(u2, 1), 1);
         try bit_stream.writeBits(@as(u5, 2), 2);
@@ -80,7 +80,7 @@ test "BitStreams with File Stream" {
         var file = try tmp.dir.openFile(tmp_file_name, .{});
         defer file.close();
 
-        var bit_stream = io.bitReader(native_endian, file.deprecatedReader());
+        var bit_stream = Io.bitReader(native_endian, file.deprecatedReader());
 
         var out_bits: u16 = undefined;
 
@@ -170,7 +170,7 @@ test "updateTimes" {
 
 test "GenericReader methods can return error.EndOfStream" {
     // https://github.com/ziglang/zig/issues/17733
-    var fbs = std.io.fixedBufferStream("");
+    var fbs = std.Io.fixedBufferStream("");
     try std.testing.expectError(
         error.EndOfStream,
         fbs.reader().readEnum(enum(u8) { a, b }, .little),
@@ -180,3 +180,14 @@ test "GenericReader methods can return error.EndOfStream" {
         fbs.reader().isBytes("foo"),
     );
 }
+
+test "Io instance provided by unit tester async/await" {
+    const io = std.testing.io;
+    var future1 = io.async(silly, .{1});
+    var future2 = io.async(silly, .{2});
+    try std.testing.expectEqual(3, future1.await(io) + future2.await(io));
+}
+
+fn silly(n: usize) usize {
+    return n;
+}
diff --git a/lib/std/testing.zig b/lib/std/testing.zig
index f9027a4f47..7904a4ffd0 100644
--- a/lib/std/testing.zig
+++ b/lib/std/testing.zig
@@ -28,6 +28,9 @@ pub var allocator_instance: std.heap.GeneralPurposeAllocator(.{
     break :b .init;
 };
 
+pub var io_instance: std.Io.ThreadPool = undefined;
+pub const io = io_instance.io();
+
 /// TODO https://github.com/ziglang/zig/issues/5738
 pub var log_level = std.log.Level.warn;