diff --git a/crates/lb/tests/task.lua b/crates/lb/tests/task.lua
new file mode 100644
index 0000000..89d7f75
--- /dev/null
+++ b/crates/lb/tests/task.lua
@@ -0,0 +1,56 @@
+local ok, task = pcall(require, "lb:task")
+if not ok then return end
+
+describe("spawn", function()
+  test("callback receives args", function()
+    spawn(function(...)
+      assert(select("#", ...) == 0)
+    end):await()
+
+    spawn(function(...)
+      assert(select("#", ...) == 1)
+      assert((...) == nil)
+    end, nil):await()
+
+    spawn(function(...)
+      assert(select("#", ...) == 4)
+      local args = table.pack(...)
+      assert(args[1] == 1 and args[2] == 2 and args[3] == nil and args[4] == 3)
+    end, 1, 2, nil, 3):await()
+  end)
+
+  test("await returns callback results", function()
+    local res = table.pack(task
+      :spawn(function()
+        -- no returns
+      end)
+      :await())
+    assert(res.n == 0)
+
+    local res = table.pack(task
+      :spawn(function()
+        return nil
+      end)
+      :await())
+    assert(res.n == 1 and res[1] == nil)
+
+    local res = table.pack(task
+      :spawn(function()
+        return 1, 2, nil, 3
+      end)
+      :await())
+    assert(res.n == 4 and res[1] == 1 and res[2] == 2 and res[3] == nil and res[4] == 3)
+  end)
+
+  test("callback args and results", function()
+    local res = table.pack(task
+      :spawn(function(...)
+        assert(select("#", ...) == 5)
+        local args = table.pack(...)
+        assert(args[1] == 5 and args[2] == 4 and args[3] == nil and args[4] == 3, args[5] == nil)
+        return 1, 3, nil
+      end, 5, 4, nil, 3, nil)
+      :await())
+    assert(res.n == 3 and res[1] == 1 and res[2] == 3 and res[3] == nil)
+  end)
+end)