diff --git a/test/standalone/posix/build.zig b/test/standalone/posix/build.zig
index 52ec99628d..f163beea8a 100644
--- a/test/standalone/posix/build.zig
+++ b/test/standalone/posix/build.zig
@@ -4,11 +4,13 @@ const builtin = @import("builtin");
 const Case = struct {
     src_path: []const u8,
     set_env_vars: bool = false,
+    make_tmp_dir: bool = false,
 };
 
 const cases = [_]Case{
     .{
         .src_path = "cwd.zig",
+        .make_tmp_dir = true,
     },
     .{
         .src_path = "getenv.zig",
@@ -19,6 +21,7 @@ const cases = [_]Case{
     },
     .{
         .src_path = "relpaths.zig",
+        .make_tmp_dir = true,
     },
 };
 
@@ -69,6 +72,9 @@ fn run_exe(b: *std.Build, optimize: std.builtin.OptimizeMode, case: *const Case,
     });
 
     const run_cmd = b.addRunArtifact(exe);
+    if (case.make_tmp_dir) {
+        run_cmd.addDirectoryArg(b.tmpPath());
+    }
 
     if (case.set_env_vars) {
         run_cmd.setEnvironmentVariable("ZIG_TEST_POSIX_1EQ", "test=variable");
diff --git a/test/standalone/posix/cwd.zig b/test/standalone/posix/cwd.zig
index d437132475..7a9517b412 100644
--- a/test/standalone/posix/cwd.zig
+++ b/test/standalone/posix/cwd.zig
@@ -13,10 +13,15 @@ pub fn main(init: std.process.Init) !void {
         .windows => return, // POSIX is not implemented by Windows
         else => {},
     }
+    const args = try init.minimal.args.toSlice(init.arena.allocator());
+    const tmp_dir_path = args[1];
+
+    var tmp_dir = try Io.Dir.cwd().openDir(init.io, tmp_dir_path, .{});
+    defer tmp_dir.close(init.io);
 
     try test_chdir_self();
     try test_chdir_absolute();
-    try test_chdir_relative(init.gpa, init.io);
+    try test_chdir_relative(init.gpa, init.io, tmp_dir);
 }
 
 // get current working directory and expect it to match given path
@@ -47,23 +52,22 @@ fn test_chdir_absolute() !void {
     try expect_cwd(parent);
 }
 
-fn test_chdir_relative(gpa: Allocator, io: Io) !void {
-    var tmp = tmpDir(io, .{});
-    defer tmp.cleanup(io);
+fn test_chdir_relative(gpa: Allocator, io: Io, tmp_dir: Io.Dir) !void {
+    const subdir_path = "subdir";
+    try tmp_dir.createDir(io, "subdir", .default_dir);
 
-    // Use the tmpDir parent_dir as the "base" for the test. Then cd into the child
-    try std.process.setCurrentDir(io, tmp.parent_dir);
+    // Use the tmp dir as the "base" for the test. Then cd into the child
+    try std.process.setCurrentDir(io, tmp_dir);
 
     // Capture base working directory path, to build expected full path
     var base_cwd_buf: [path_max]u8 = undefined;
     const base_cwd = try std.posix.getcwd(base_cwd_buf[0..]);
 
-    const relative_dir_name = &tmp.sub_path;
-    const expected_path = try std.fs.path.resolve(gpa, &.{ base_cwd, relative_dir_name });
+    const expected_path = try std.fs.path.resolve(gpa, &.{ base_cwd, subdir_path });
     defer gpa.free(expected_path);
 
     // change current working directory to new test directory
-    try std.Io.Threaded.chdir(relative_dir_name);
+    try std.Io.Threaded.chdir(subdir_path);
 
     var new_cwd_buf: [path_max]u8 = undefined;
     const new_cwd = try std.posix.getcwd(new_cwd_buf[0..]);
@@ -74,41 +78,3 @@ fn test_chdir_relative(gpa: Allocator, io: Io) !void {
 
     try std.testing.expectEqualStrings(expected_path, resolved_cwd);
 }
-
-pub fn tmpDir(io: Io, opts: Io.Dir.OpenOptions) TmpDir {
-    var random_bytes: [TmpDir.random_bytes_count]u8 = undefined;
-    std.crypto.random.bytes(&random_bytes);
-    var sub_path: [TmpDir.sub_path_len]u8 = undefined;
-    _ = std.fs.base64_encoder.encode(&sub_path, &random_bytes);
-
-    const cwd = Io.Dir.cwd();
-    var cache_dir = cwd.createDirPathOpen(io, ".zig-cache", .{}) catch
-        @panic("unable to make tmp dir for testing: unable to make and open .zig-cache dir");
-    defer cache_dir.close(io);
-    const parent_dir = cache_dir.createDirPathOpen(io, "tmp", .{}) catch
-        @panic("unable to make tmp dir for testing: unable to make and open .zig-cache/tmp dir");
-    const dir = parent_dir.createDirPathOpen(io, &sub_path, .{ .open_options = opts }) catch
-        @panic("unable to make tmp dir for testing: unable to make and open the tmp dir");
-
-    return .{
-        .dir = dir,
-        .parent_dir = parent_dir,
-        .sub_path = sub_path,
-    };
-}
-
-pub const TmpDir = struct {
-    dir: Io.Dir,
-    parent_dir: Io.Dir,
-    sub_path: [sub_path_len]u8,
-
-    const random_bytes_count = 12;
-    const sub_path_len = std.fs.base64_encoder.calcSize(random_bytes_count);
-
-    pub fn cleanup(self: *TmpDir, io: Io) void {
-        self.dir.close(io);
-        self.parent_dir.deleteTree(io, &self.sub_path) catch {};
-        self.parent_dir.close(io);
-        self.* = undefined;
-    }
-};
diff --git a/test/standalone/posix/relpaths.zig b/test/standalone/posix/relpaths.zig
index e31e497875..9fe92f3cef 100644
--- a/test/standalone/posix/relpaths.zig
+++ b/test/standalone/posix/relpaths.zig
@@ -11,16 +11,19 @@ pub fn main(init: std.process.Init) !void {
 
     const io = init.io;
 
-    var tmp = tmpDir(io, .{});
-    defer tmp.cleanup(io);
+    const args = try init.minimal.args.toSlice(init.arena.allocator());
+    const tmp_dir_path = args[1];
+
+    var tmp_dir = try Io.Dir.cwd().openDir(io, tmp_dir_path, .{});
+    defer tmp_dir.close(io);
 
     // Want to test relative paths, so cd into the tmpdir for these tests
-    try std.process.setCurrentDir(io, tmp.dir);
+    try std.process.setCurrentDir(io, tmp_dir);
 
-    try test_link(io, tmp);
+    try test_link(io, tmp_dir);
 }
 
-fn test_link(io: Io, tmp: TmpDir) !void {
+fn test_link(io: Io, tmp_dir: Io.Dir) !void {
     switch (builtin.target.os.tag) {
         .linux, .illumos => {},
         else => return,
@@ -29,16 +32,16 @@ fn test_link(io: Io, tmp: TmpDir) !void {
     const target_name = "link-target";
     const link_name = "newlink";
 
-    try tmp.dir.writeFile(io, .{ .sub_path = target_name, .data = "example" });
+    try tmp_dir.writeFile(io, .{ .sub_path = target_name, .data = "example" });
 
-    // Test 1: create the relative link from inside tmp
+    // Test 1: create the relative link from inside tmp_dir
     try Io.Dir.hardLink(.cwd(), target_name, .cwd(), link_name, io, .{});
 
     // Verify
-    const efd = try tmp.dir.openFile(io, target_name, .{});
+    const efd = try tmp_dir.openFile(io, target_name, .{});
     defer efd.close(io);
 
-    const nfd = try tmp.dir.openFile(io, link_name, .{});
+    const nfd = try tmp_dir.openFile(io, link_name, .{});
     defer nfd.close(io);
 
     {
@@ -55,41 +58,3 @@ fn test_link(io: Io, tmp: TmpDir) !void {
         try std.testing.expectEqual(1, e_stat.nlink);
     }
 }
-
-pub fn tmpDir(io: Io, opts: Io.Dir.OpenOptions) TmpDir {
-    var random_bytes: [TmpDir.random_bytes_count]u8 = undefined;
-    std.crypto.random.bytes(&random_bytes);
-    var sub_path: [TmpDir.sub_path_len]u8 = undefined;
-    _ = std.fs.base64_encoder.encode(&sub_path, &random_bytes);
-
-    const cwd = Io.Dir.cwd();
-    var cache_dir = cwd.createDirPathOpen(io, ".zig-cache", .{}) catch
-        @panic("unable to make tmp dir for testing: unable to make and open .zig-cache dir");
-    defer cache_dir.close(io);
-    const parent_dir = cache_dir.createDirPathOpen(io, "tmp", .{}) catch
-        @panic("unable to make tmp dir for testing: unable to make and open .zig-cache/tmp dir");
-    const dir = parent_dir.createDirPathOpen(io, &sub_path, .{ .open_options = opts }) catch
-        @panic("unable to make tmp dir for testing: unable to make and open the tmp dir");
-
-    return .{
-        .dir = dir,
-        .parent_dir = parent_dir,
-        .sub_path = sub_path,
-    };
-}
-
-pub const TmpDir = struct {
-    dir: Io.Dir,
-    parent_dir: Io.Dir,
-    sub_path: [sub_path_len]u8,
-
-    const random_bytes_count = 12;
-    const sub_path_len = std.fs.base64_encoder.calcSize(random_bytes_count);
-
-    pub fn cleanup(self: *TmpDir, io: Io) void {
-        self.dir.close(io);
-        self.parent_dir.deleteTree(io, &self.sub_path) catch {};
-        self.parent_dir.close(io);
-        self.* = undefined;
-    }
-};
diff --git a/test/standalone/windows_bat_args/build.zig b/test/standalone/windows_bat_args/build.zig
index b91b4fb3bb..d54b6cd48c 100644
--- a/test/standalone/windows_bat_args/build.zig
+++ b/test/standalone/windows_bat_args/build.zig
@@ -19,6 +19,22 @@ pub fn build(b: *std.Build) !void {
         }),
     });
 
+    const bat_files = b.addWriteFiles();
+    {
+        const echo_args_basename = "echo-args.exe";
+        const preamble = std.fmt.allocPrint(b.allocator,
+            \\@echo off
+            \\"{s}"
+        , .{echo_args_basename}) catch @panic("OOM");
+        // Trailing newline intentionally omitted above so we can add args.
+
+        _ = bat_files.add("args1.bat", std.mem.concat(b.allocator, u8, &.{ preamble, " %*" }) catch @panic("OOM"));
+        _ = bat_files.add("args2.bat", std.mem.concat(b.allocator, u8, &.{ preamble, " %1 %2 %3 %4 %5 %6 %7 %8 %9" }) catch @panic("OOM"));
+        _ = bat_files.add("args3.bat", std.mem.concat(b.allocator, u8, &.{ preamble, " \"%~1\" \"%~2\" \"%~3\" \"%~4\" \"%~5\" \"%~6\" \"%~7\" \"%~8\" \"%~9\"" }) catch @panic("OOM"));
+
+        _ = bat_files.addCopyFile(echo_args.getEmittedBin(), echo_args_basename);
+    }
+
     const test_exe = b.addExecutable(.{
         .name = "test",
         .root_module = b.createModule(.{
@@ -29,7 +45,7 @@ pub fn build(b: *std.Build) !void {
     });
 
     const run = b.addRunArtifact(test_exe);
-    run.addArtifactArg(echo_args);
+    run.setCwd(bat_files.getDirectory());
     run.expectExitCode(0);
     run.skip_foreign_checks = true;
 
@@ -55,7 +71,7 @@ pub fn build(b: *std.Build) !void {
     const fuzz_seed_arg = std.fmt.allocPrint(b.allocator, "{}", .{fuzz_seed}) catch @panic("oom");
 
     const fuzz_run = b.addRunArtifact(fuzz);
-    fuzz_run.addArtifactArg(echo_args);
+    fuzz_run.setCwd(bat_files.getDirectory());
     fuzz_run.addArgs(&.{ fuzz_iterations_arg, fuzz_seed_arg });
     fuzz_run.expectExitCode(0);
     fuzz_run.skip_foreign_checks = true;
diff --git a/test/standalone/windows_bat_args/fuzz.zig b/test/standalone/windows_bat_args/fuzz.zig
index b82ec8b458..f3f72ab897 100644
--- a/test/standalone/windows_bat_args/fuzz.zig
+++ b/test/standalone/windows_bat_args/fuzz.zig
@@ -11,7 +11,6 @@ pub fn main(init: std.process.Init) !void {
     var it = try init.minimal.args.iterateAllocator(gpa);
     defer it.deinit();
     _ = it.next() orelse unreachable; // skip binary name
-    const child_exe_path_orig = it.next() orelse unreachable;
 
     const iterations: u64 = iterations: {
         const arg = it.next() orelse "0";
@@ -37,37 +36,6 @@ pub fn main(init: std.process.Init) !void {
         std.debug.print("rand seed: {}\n", .{seed});
     }
 
-    var tmp = tmpDir(io, .{});
-    defer tmp.cleanup(io);
-
-    try std.process.setCurrentDir(io, tmp.dir);
-    defer std.process.setCurrentDir(io, tmp.parent_dir) catch {};
-
-    // `child_exe_path_orig` might be relative; make it relative to our new cwd.
-    const child_exe_path = try std.fs.path.resolve(gpa, &.{ "..\\..\\..", child_exe_path_orig });
-    defer gpa.free(child_exe_path);
-
-    var buf: std.ArrayList(u8) = .empty;
-    defer buf.deinit(gpa);
-    try buf.print(gpa,
-        \\@echo off
-        \\"{s}"
-    , .{child_exe_path});
-    // Trailing newline intentionally omitted above so we can add args.
-    const preamble_len = buf.items.len;
-
-    try buf.appendSlice(gpa, " %*");
-    try tmp.dir.writeFile(io, .{ .sub_path = "args1.bat", .data = buf.items });
-    buf.shrinkRetainingCapacity(preamble_len);
-
-    try buf.appendSlice(gpa, " %1 %2 %3 %4 %5 %6 %7 %8 %9");
-    try tmp.dir.writeFile(io, .{ .sub_path = "args2.bat", .data = buf.items });
-    buf.shrinkRetainingCapacity(preamble_len);
-
-    try buf.appendSlice(gpa, " \"%~1\" \"%~2\" \"%~3\" \"%~4\" \"%~5\" \"%~6\" \"%~7\" \"%~8\" \"%~9\"");
-    try tmp.dir.writeFile(io, .{ .sub_path = "args3.bat", .data = buf.items });
-    buf.shrinkRetainingCapacity(preamble_len);
-
     var i: u64 = 0;
     while (iterations == 0 or i < iterations) {
         const rand_arg = try randomArg(gpa, rand);
@@ -163,41 +131,3 @@ fn randomArg(gpa: Allocator, rand: std.Random) ![]const u8 {
 
     return buf.toOwnedSlice(gpa);
 }
-
-pub fn tmpDir(io: Io, opts: Io.Dir.OpenOptions) TmpDir {
-    var random_bytes: [TmpDir.random_bytes_count]u8 = undefined;
-    std.crypto.random.bytes(&random_bytes);
-    var sub_path: [TmpDir.sub_path_len]u8 = undefined;
-    _ = std.fs.base64_encoder.encode(&sub_path, &random_bytes);
-
-    const cwd = Io.Dir.cwd();
-    var cache_dir = cwd.createDirPathOpen(io, ".zig-cache", .{}) catch
-        @panic("unable to make tmp dir for testing: unable to make and open .zig-cache dir");
-    defer cache_dir.close(io);
-    const parent_dir = cache_dir.createDirPathOpen(io, "tmp", .{}) catch
-        @panic("unable to make tmp dir for testing: unable to make and open .zig-cache/tmp dir");
-    const dir = parent_dir.createDirPathOpen(io, &sub_path, .{ .open_options = opts }) catch
-        @panic("unable to make tmp dir for testing: unable to make and open the tmp dir");
-
-    return .{
-        .dir = dir,
-        .parent_dir = parent_dir,
-        .sub_path = sub_path,
-    };
-}
-
-pub const TmpDir = struct {
-    dir: Io.Dir,
-    parent_dir: Io.Dir,
-    sub_path: [sub_path_len]u8,
-
-    const random_bytes_count = 12;
-    const sub_path_len = std.fs.base64_encoder.calcSize(random_bytes_count);
-
-    pub fn cleanup(self: *TmpDir, io: Io) void {
-        self.dir.close(io);
-        self.parent_dir.deleteTree(io, &self.sub_path) catch {};
-        self.parent_dir.close(io);
-        self.* = undefined;
-    }
-};
diff --git a/test/standalone/windows_bat_args/test.zig b/test/standalone/windows_bat_args/test.zig
index fde627a5fe..a923326aa1 100644
--- a/test/standalone/windows_bat_args/test.zig
+++ b/test/standalone/windows_bat_args/test.zig
@@ -6,42 +6,6 @@ pub fn main(init: std.process.Init) !void {
     const gpa = init.gpa;
     const io = init.io;
 
-    var it = try init.minimal.args.iterateAllocator(gpa);
-    defer it.deinit();
-    _ = it.next() orelse unreachable; // skip binary name
-    const child_exe_path_orig = it.next() orelse unreachable;
-
-    var tmp = tmpDir(io, .{});
-    defer tmp.cleanup(io);
-
-    try std.process.setCurrentDir(io, tmp.dir);
-    defer std.process.setCurrentDir(io, tmp.parent_dir) catch {};
-
-    // `child_exe_path_orig` might be relative; make it relative to our new cwd.
-    const child_exe_path = try std.fs.path.resolve(gpa, &.{ "..\\..\\..", child_exe_path_orig });
-    defer gpa.free(child_exe_path);
-
-    var buf: std.ArrayList(u8) = .empty;
-    defer buf.deinit(gpa);
-    try buf.print(gpa,
-        \\@echo off
-        \\"{s}"
-    , .{child_exe_path});
-    // Trailing newline intentionally omitted above so we can add args.
-    const preamble_len = buf.items.len;
-
-    try buf.appendSlice(gpa, " %*");
-    try tmp.dir.writeFile(io, .{ .sub_path = "args1.bat", .data = buf.items });
-    buf.shrinkRetainingCapacity(preamble_len);
-
-    try buf.appendSlice(gpa, " %1 %2 %3 %4 %5 %6 %7 %8 %9");
-    try tmp.dir.writeFile(io, .{ .sub_path = "args2.bat", .data = buf.items });
-    buf.shrinkRetainingCapacity(preamble_len);
-
-    try buf.appendSlice(gpa, " \"%~1\" \"%~2\" \"%~3\" \"%~4\" \"%~5\" \"%~6\" \"%~7\" \"%~8\" \"%~9\"");
-    try tmp.dir.writeFile(io, .{ .sub_path = "args3.bat", .data = buf.items });
-    buf.shrinkRetainingCapacity(preamble_len);
-
     // Test cases are from https://github.com/rust-lang/rust/blob/master/tests/ui/std/windows-bat-args.rs
     try testExecError(error.InvalidBatchScriptArg, gpa, io, &.{"\x00"});
     try testExecError(error.InvalidBatchScriptArg, gpa, io, &.{"\n"});
@@ -119,7 +83,7 @@ pub fn main(init: std.process.Init) !void {
     try testExec(gpa, io, &.{"%FOO%"}, &env);
 
     // Ensure that none of the `>file.txt`s have caused file.txt to be created
-    try std.testing.expectError(error.FileNotFound, tmp.dir.access(io, "file.txt", .{}));
+    try std.testing.expectError(error.FileNotFound, Io.Dir.cwd().access(io, "file.txt", .{}));
 }
 
 fn testExecError(err: anyerror, gpa: Allocator, io: Io, args: []const []const u8) !void {
@@ -160,41 +124,3 @@ fn testExecBat(gpa: Allocator, io: Io, bat: []const u8, args: []const []const u8
         i += 1;
     }
 }
-
-pub fn tmpDir(io: Io, opts: Io.Dir.OpenOptions) TmpDir {
-    var random_bytes: [TmpDir.random_bytes_count]u8 = undefined;
-    std.crypto.random.bytes(&random_bytes);
-    var sub_path: [TmpDir.sub_path_len]u8 = undefined;
-    _ = std.fs.base64_encoder.encode(&sub_path, &random_bytes);
-
-    const cwd = Io.Dir.cwd();
-    var cache_dir = cwd.createDirPathOpen(io, ".zig-cache", .{}) catch
-        @panic("unable to make tmp dir for testing: unable to make and open .zig-cache dir");
-    defer cache_dir.close(io);
-    const parent_dir = cache_dir.createDirPathOpen(io, "tmp", .{}) catch
-        @panic("unable to make tmp dir for testing: unable to make and open .zig-cache/tmp dir");
-    const dir = parent_dir.createDirPathOpen(io, &sub_path, .{ .open_options = opts }) catch
-        @panic("unable to make tmp dir for testing: unable to make and open the tmp dir");
-
-    return .{
-        .dir = dir,
-        .parent_dir = parent_dir,
-        .sub_path = sub_path,
-    };
-}
-
-pub const TmpDir = struct {
-    dir: Io.Dir,
-    parent_dir: Io.Dir,
-    sub_path: [sub_path_len]u8,
-
-    const random_bytes_count = 12;
-    const sub_path_len = std.fs.base64_encoder.calcSize(random_bytes_count);
-
-    pub fn cleanup(self: *TmpDir, io: Io) void {
-        self.dir.close(io);
-        self.parent_dir.deleteTree(io, &self.sub_path) catch {};
-        self.parent_dir.close(io);
-        self.* = undefined;
-    }
-};
diff --git a/test/standalone/windows_spawn/build.zig b/test/standalone/windows_spawn/build.zig
index 2b967b16d5..43b0f162bf 100644
--- a/test/standalone/windows_spawn/build.zig
+++ b/test/standalone/windows_spawn/build.zig
@@ -30,6 +30,7 @@ pub fn build(b: *std.Build) void {
 
     const run = b.addRunArtifact(main);
     run.addArtifactArg(hello);
+    run.addDirectoryArg(b.tmpPath());
     run.expectExitCode(0);
     run.skip_foreign_checks = true;
 
diff --git a/test/standalone/windows_spawn/main.zig b/test/standalone/windows_spawn/main.zig
index 4a64ca48d6..e26b581f59 100644
--- a/test/standalone/windows_spawn/main.zig
+++ b/test/standalone/windows_spawn/main.zig
@@ -9,16 +9,19 @@ pub fn main(init: std.process.Init) !void {
     const gpa = init.gpa;
     const io = init.io;
     const process_cwd_path = try std.process.getCwdAlloc(init.arena.allocator());
+    var initial_process_cwd = try Io.Dir.cwd().openDir(io, ".", .{});
+    defer initial_process_cwd.close(io);
 
     var it = try init.minimal.args.iterateAllocator(gpa);
     defer it.deinit();
     _ = it.next() orelse unreachable; // skip binary name
     const hello_exe_cache_path = it.next() orelse unreachable;
+    const tmp_dir_path = it.next() orelse unreachable;
 
-    var tmp = tmpDir(io, .{});
-    defer tmp.cleanup(io);
+    var tmp_dir = try Io.Dir.cwd().openDir(io, tmp_dir_path, .{});
+    defer tmp_dir.close(io);
 
-    const tmp_absolute_path = try tmp.dir.realPathFileAlloc(io, ".", gpa);
+    const tmp_absolute_path = try tmp_dir.realPathFileAlloc(io, ".", gpa);
     defer gpa.free(tmp_absolute_path);
     const tmp_absolute_path_w = try std.unicode.utf8ToUtf16LeAllocZ(gpa, tmp_absolute_path);
     defer gpa.free(tmp_absolute_path_w);
@@ -51,7 +54,7 @@ pub fn main(init: std.process.Init) !void {
     ) == windows.TRUE);
 
     // Move hello.exe into the tmp dir which is now added to the path
-    try Io.Dir.cwd().copyFile(hello_exe_cache_path, tmp.dir, "hello.exe", io, .{});
+    try Io.Dir.cwd().copyFile(hello_exe_cache_path, tmp_dir, "hello.exe", io, .{});
 
     // with extension should find the .exe (case insensitive)
     try testExec(gpa, io, "HeLLo.exe", "hello from exe\n");
@@ -61,9 +64,9 @@ pub fn main(init: std.process.Init) !void {
     try std.testing.expectError(error.FileNotFound, testExecWithCwd(gpa, io, "hello.exe", "missing_dir", ""));
 
     // now add a .bat
-    try tmp.dir.writeFile(io, .{ .sub_path = "hello.bat", .data = "@echo hello from bat" });
+    try tmp_dir.writeFile(io, .{ .sub_path = "hello.bat", .data = "@echo hello from bat" });
     // and a .cmd
-    try tmp.dir.writeFile(io, .{ .sub_path = "hello.cmd", .data = "@echo hello from cmd" });
+    try tmp_dir.writeFile(io, .{ .sub_path = "hello.cmd", .data = "@echo hello from cmd" });
 
     // with extension should find the .bat (case insensitive)
     try testExec(gpa, io, "heLLo.bat", "hello from bat\r\n");
@@ -73,15 +76,15 @@ pub fn main(init: std.process.Init) !void {
     try testExec(gpa, io, "heLLo", "hello from exe\n");
 
     // now rename the exe to not have an extension
-    try renameExe(tmp.dir, io, "hello.exe", "hello");
+    try renameExe(tmp_dir, io, "hello.exe", "hello");
 
     // with extension should now fail
     try testExecError(error.FileNotFound, gpa, io, "hello.exe");
     // without extension should succeed (case insensitive)
     try testExec(gpa, io, "heLLo", "hello from exe\n");
 
-    try tmp.dir.createDir(io, "something", .default_dir);
-    try renameExe(tmp.dir, io, "hello", "something/hello.exe");
+    try tmp_dir.createDir(io, "something", .default_dir);
+    try renameExe(tmp_dir, io, "hello", "something/hello.exe");
 
     const relative_path_no_ext = try std.fs.path.join(gpa, &.{ tmp_relative_path, "something/hello" });
     defer gpa.free(relative_path_no_ext);
@@ -95,7 +98,7 @@ pub fn main(init: std.process.Init) !void {
     try testExec(gpa, io, "heLLo", "hello from bat\r\n");
 
     // Add a hello.exe that is not a valid executable
-    try tmp.dir.writeFile(io, .{ .sub_path = "hello.exe", .data = "invalid" });
+    try tmp_dir.writeFile(io, .{ .sub_path = "hello.exe", .data = "invalid" });
 
     // Trying to execute it with extension will give InvalidExe. This is a special
     // case for .EXE extensions, where if they ever try to get executed but they are
@@ -108,14 +111,14 @@ pub fn main(init: std.process.Init) !void {
     try testExecError(error.InvalidExe, gpa, io, "hello");
 
     // If we now rename hello.exe to have no extension, it will behave differently
-    try renameExe(tmp.dir, io, "hello.exe", "hello");
+    try renameExe(tmp_dir, io, "hello.exe", "hello");
 
     // Now, trying to execute it without an extension should treat InvalidExe as recoverable
     // and skip over it and find hello.bat and execute that
     try testExec(gpa, io, "hello", "hello from bat\r\n");
 
     // If we rename the invalid exe to something else
-    try renameExe(tmp.dir, io, "hello", "goodbye");
+    try renameExe(tmp_dir, io, "hello", "goodbye");
     // Then we should now get FileNotFound when trying to execute 'goodbye',
     // since that is what the original error will be after searching for 'goodbye'
     // in the cwd. It will try to execute 'goodbye' from the PATH but the InvalidExe error
@@ -123,8 +126,8 @@ pub fn main(init: std.process.Init) !void {
     try testExecError(error.FileNotFound, gpa, io, "goodbye");
 
     // Now let's set the tmp dir as the cwd and set the path only include the "something" sub dir
-    try std.process.setCurrentDir(io, tmp.dir);
-    defer std.process.setCurrentDir(io, tmp.parent_dir) catch {};
+    try std.process.setCurrentDir(io, tmp_dir);
+    defer std.process.setCurrentDir(io, initial_process_cwd) catch {};
     const something_subdir_abs_path = try std.mem.concatWithSentinel(gpa, u16, &.{ tmp_absolute_path_w, utf16Literal("\\something") }, 0);
     defer gpa.free(something_subdir_abs_path);
 
@@ -141,7 +144,7 @@ pub fn main(init: std.process.Init) !void {
     try testExec(gpa, io, "hello", "hello from bat\r\n");
 
     // If we rename something/hello.exe to something/goodbye.exe
-    try renameExe(tmp.dir, io, "something/hello.exe", "something/goodbye.exe");
+    try renameExe(tmp_dir, io, "something/hello.exe", "something/goodbye.exe");
     // And try to execute goodbye, then the one in something should be found
     // since the one in cwd is an invalid executable
     try testExec(gpa, io, "goodbye", "hello from exe\n");
@@ -183,10 +186,10 @@ pub fn main(init: std.process.Init) !void {
     try testExec(gpa, io, "goodbye", "hello from exe\n");
 
     // now make sure we can launch executables "outside" of the cwd
-    var subdir_cwd = try tmp.dir.openDir(io, denormed_something_subdir_wtf8, .{});
+    var subdir_cwd = try tmp_dir.openDir(io, denormed_something_subdir_wtf8, .{});
     defer subdir_cwd.close(io);
 
-    try renameExe(tmp.dir, io, "something/goodbye.exe", "hello.exe");
+    try renameExe(tmp_dir, io, "something/goodbye.exe", "hello.exe");
     try std.process.setCurrentDir(io, subdir_cwd);
 
     // clear the PATH again
@@ -232,41 +235,3 @@ fn renameExe(dir: Io.Dir, io: Io, old_sub_path: []const u8, new_sub_path: []cons
         else => |e| return e,
     };
 }
-
-pub fn tmpDir(io: Io, opts: Io.Dir.OpenOptions) TmpDir {
-    var random_bytes: [TmpDir.random_bytes_count]u8 = undefined;
-    std.crypto.random.bytes(&random_bytes);
-    var sub_path: [TmpDir.sub_path_len]u8 = undefined;
-    _ = std.fs.base64_encoder.encode(&sub_path, &random_bytes);
-
-    const cwd = Io.Dir.cwd();
-    var cache_dir = cwd.createDirPathOpen(io, ".zig-cache", .{}) catch
-        @panic("unable to make tmp dir for testing: unable to make and open .zig-cache dir");
-    defer cache_dir.close(io);
-    const parent_dir = cache_dir.createDirPathOpen(io, "tmp", .{}) catch
-        @panic("unable to make tmp dir for testing: unable to make and open .zig-cache/tmp dir");
-    const dir = parent_dir.createDirPathOpen(io, &sub_path, .{ .open_options = opts }) catch
-        @panic("unable to make tmp dir for testing: unable to make and open the tmp dir");
-
-    return .{
-        .dir = dir,
-        .parent_dir = parent_dir,
-        .sub_path = sub_path,
-    };
-}
-
-pub const TmpDir = struct {
-    dir: Io.Dir,
-    parent_dir: Io.Dir,
-    sub_path: [sub_path_len]u8,
-
-    const random_bytes_count = 12;
-    const sub_path_len = std.fs.base64_encoder.calcSize(random_bytes_count);
-
-    pub fn cleanup(self: *TmpDir, io: Io) void {
-        self.dir.close(io);
-        self.parent_dir.deleteTree(io, &self.sub_path) catch {};
-        self.parent_dir.close(io);
-        self.* = undefined;
-    }
-};