diff --git a/src/TestHTTPServer.zig b/src/TestHTTPServer.zig
index 9750a396..19c5bbc9 100644
--- a/src/TestHTTPServer.zig
+++ b/src/TestHTTPServer.zig
@@ -20,7 +20,7 @@ const std = @import("std");
 
 const TestHTTPServer = @This();
 
-shutdown: bool,
+shutdown: std.atomic.Value(bool),
 listener: ?std.net.Server,
 handler: Handler,
 
@@ -28,16 +28,22 @@ const Handler = *const fn (req: *std.http.Server.Request) anyerror!void;
 
 pub fn init(handler: Handler) TestHTTPServer {
     return .{
-        .shutdown = true,
+        .shutdown = .init(true),
         .listener = null,
         .handler = handler,
     };
 }
 
 pub fn deinit(self: *TestHTTPServer) void {
-    self.shutdown = true;
+    self.listener = null;
+}
+
+pub fn stop(self: *TestHTTPServer) void {
+    self.shutdown.store(true, .release);
     if (self.listener) |*listener| {
-        listener.deinit();
+        // Use shutdown to unblock accept(). On Linux this causes accept to
+        // return error.SocketNotListening. close() alone doesn't interrupt accept().
+        std.posix.shutdown(listener.stream.handle, .recv) catch {};
     }
 }
 
@@ -46,12 +52,13 @@ pub fn run(self: *TestHTTPServer, wg: *std.Thread.WaitGroup) !void {
 
     self.listener = try address.listen(.{ .reuse_address = true });
     var listener = &self.listener.?;
+    self.shutdown.store(false, .release);
 
     wg.finish();
 
     while (true) {
         const conn = listener.accept() catch |err| {
-            if (self.shutdown) {
+            if (self.shutdown.load(.acquire) or err == error.SocketNotListening) {
                 return;
             }
             return err;
diff --git a/src/test_runner.zig b/src/test_runner.zig
index 2461c82f..1b9a2324 100644
--- a/src/test_runner.zig
+++ b/src/test_runner.zig
@@ -442,6 +442,7 @@ pub const TrackingAllocator = struct {
     allocated_bytes: usize = 0,
     allocation_count: usize = 0,
     reallocation_count: usize = 0,
+    mutex: std.Thread.Mutex = .{},
 
     const Stats = struct {
         allocated_bytes: usize,
@@ -479,6 +480,9 @@ pub const TrackingAllocator = struct {
         return_address: usize,
     ) ?[*]u8 {
         const self: *TrackingAllocator = @ptrCast(@alignCast(ctx));
+        self.mutex.lock();
+        defer self.mutex.unlock();
+
         const result = self.parent_allocator.rawAlloc(len, alignment, return_address);
         self.allocation_count += 1;
         self.allocated_bytes += len;
@@ -493,6 +497,9 @@ pub const TrackingAllocator = struct {
         ra: usize,
     ) bool {
         const self: *TrackingAllocator = @ptrCast(@alignCast(ctx));
+        self.mutex.lock();
+        defer self.mutex.unlock();
+
         const result = self.parent_allocator.rawResize(old_mem, alignment, new_len, ra);
         self.reallocation_count += 1; // TODO: only if result is not null?
         return result;
@@ -505,6 +512,9 @@ pub const TrackingAllocator = struct {
         ra: usize,
     ) void {
         const self: *TrackingAllocator = @ptrCast(@alignCast(ctx));
+        self.mutex.lock();
+        defer self.mutex.unlock();
+
         self.parent_allocator.rawFree(old_mem, alignment, ra);
         self.free_count += 1;
     }
@@ -517,6 +527,9 @@ pub const TrackingAllocator = struct {
         ret_addr: usize,
     ) ?[*]u8 {
         const self: *TrackingAllocator = @ptrCast(@alignCast(ctx));
+        self.mutex.lock();
+        defer self.mutex.unlock();
+
         const result = self.parent_allocator.rawRemap(memory, alignment, new_len, ret_addr);
         self.reallocation_count += 1; // TODO: only if result is not null?
         return result;
diff --git a/src/testing.zig b/src/testing.zig
index 05c7efbc..41f67e96 100644
--- a/src/testing.zig
+++ b/src/testing.zig
@@ -450,7 +450,9 @@ const TestHTTPServer = @import("TestHTTPServer.zig");
 
 const Server = @import("Server.zig");
 var test_cdp_server: ?Server = null;
+var test_cdp_server_thread: ?std.Thread = null;
 var test_http_server: ?TestHTTPServer = null;
+var test_http_server_thread: ?std.Thread = null;
 
 var test_config: Config = undefined;
 
@@ -482,16 +484,10 @@ test "tests:beforeAll" {
     var wg: std.Thread.WaitGroup = .{};
     wg.startMany(2);
 
-    {
-        const thread = try std.Thread.spawn(.{}, serveCDP, .{&wg});
-        thread.detach();
-    }
+    test_cdp_server_thread = try std.Thread.spawn(.{}, serveCDP, .{&wg});
 
     test_http_server = TestHTTPServer.init(testHTTPHandler);
-    {
-        const thread = try std.Thread.spawn(.{}, TestHTTPServer.run, .{ &test_http_server.?, &wg });
-        thread.detach();
-    }
+    test_http_server_thread = try std.Thread.spawn(.{}, TestHTTPServer.run, .{ &test_http_server.?, &wg });
 
     // need to wait for the servers to be listening, else tests will fail because
     // they aren't able to connect.
@@ -499,9 +495,22 @@ test "tests:beforeAll" {
 }
 
 test "tests:afterAll" {
+    if (test_cdp_server) |*server| {
+        server.stop();
+    }
+    if (test_cdp_server_thread) |thread| {
+        thread.join();
+    }
     if (test_cdp_server) |*server| {
         server.deinit();
     }
+
+    if (test_http_server) |*server| {
+        server.stop();
+    }
+    if (test_http_server_thread) |thread| {
+        thread.join();
+    }
     if (test_http_server) |*server| {
         server.deinit();
     }
@@ -518,8 +527,6 @@ fn serveCDP(wg: *std.Thread.WaitGroup) !void {
     const address = try std.net.Address.parseIp("127.0.0.1", 9583);
     test_cdp_server = try Server.init(test_app, address);
 
-    var server = try Server.init(test_app, address);
-    defer server.deinit();
     wg.finish();
 
     test_cdp_server.?.run(address, 5) catch |err| {