diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 61a0dc8..12a15de 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -1,20 +1,20 @@
 name: test
 
-on: [push]
+on:
+  push:
+    paths-ignore:
+      - '**.md'
+      - 'LICENSE'
 
 jobs:
   luacheck:
     runs-on: ubuntu-latest
+    container:
+      image: ghcr.io/mah0x211/lua-ci:latest
     steps:
     -
       name: Checkout
       uses: actions/checkout@v2
-    -
-      name: Setup Lua
-      uses: leafo/gh-actions-lua@v8.0.0
-    -
-      name: Setup Luarocks
-      uses: leafo/gh-actions-luarocks@v4
     -
       name: Install Tools
       run: luarocks install luacheck
@@ -24,50 +24,54 @@ jobs:
         luacheck .
 
   test:
+    needs: luacheck
+    permissions:
+      id-token: write
     runs-on: ubuntu-latest
+    container:
+      image: ghcr.io/mah0x211/lua-ci:latest
     strategy:
       matrix:
         lua-version:
-          - "5.1"
-          - "5.2"
-          - "5.3"
-          - "5.4"
-          - "luajit-2.0.5"
-          - "luajit-openresty"
+          - "5.1.:latest"
+          - "5.2.:latest"
+          - "5.3.:latest"
+          - "5.4.:latest"
+          - "lj-v2.1:latest"
     steps:
+    -
+      name: Switch Lua Version
+      run: |
+        lenv -g use ${{ matrix.lua-version }}
+        lua -v || true
     -
       name: Checkout
       uses: actions/checkout@v2
-      with:
-        submodules: 'true'
-    -
-      name: Setup Lua ${{ matrix.lua-version }}
-      uses: leafo/gh-actions-lua@v8.0.0
-      with:
-        luaVersion: ${{ matrix.lua-version }}
     -
-      name: Setup Luarocks
-      uses: leafo/gh-actions-luarocks@v4
+      name: Install
+      run: |
+        ACT_COVERAGE=1 luarocks make
     -
-      name: Install Test Tools
+      name: Install Tools
       run: |
         luarocks install testcase
+        luarocks install assert
         luarocks install errno
-        luarocks install llsocket
         luarocks install signal
         luarocks install luacov
-    -
-      name: Install
-      run: |
-        luarocks make
     -
       name: Run Test
       run: |
         testcase --coverage ./test/
     -
-      name: Upload lua coverage to Codecov
-      uses: codecov/codecov-action@v2
+      name: Generate coverage reports
+      run: |
+        sh ./covgen.sh
+    -
+      name: Upload coverage to Codecov
+      uses: codecov/codecov-action@v5
       with:
-        files: ./luacov.report.out
+        use_oidc: true
+        disable_search: true
+        files: ./luacov.report.out,./coverage/lcov.info
         flags: unittests
-
diff --git a/act.lua b/act.lua
index 4c8406e..666c294 100644
--- a/act.lua
+++ b/act.lua
@@ -138,7 +138,7 @@ local function pwaitpid(sec, wpid, ...)
         end
 
         while true do
-            local res, err, again = waitpid(wpid, 'nohang', ...)
+            local res, err, again = waitpid(wpid, nil, 'nohang', ...)
             if res then
                 return res
             elseif not again then
diff --git a/covgen.sh b/covgen.sh
new file mode 100755
index 0000000..700ea4b
--- /dev/null
+++ b/covgen.sh
@@ -0,0 +1,7 @@
+#!/usr/bin/env sh
+
+set -ex
+
+mkdir -p ./coverage
+lcov -c -d ./src -o coverage/lcov.info.all
+lcov -r coverage/lcov.info.all '*/include/*' -o coverage/lcov.info
diff --git a/rockspecs/act-scm-1.rockspec b/rockspecs/act-scm-1.rockspec
index b5217c7..12d880c 100644
--- a/rockspecs/act-scm-1.rockspec
+++ b/rockspecs/act-scm-1.rockspec
@@ -1,3 +1,4 @@
+rockspec_format = "3.0"
 package = "act"
 version = "scm-1"
 source = {
@@ -11,24 +12,45 @@ description = {
 }
 dependencies = {
     "lua >= 5.1",
-    "lauxhlib >= 0.5",
-    "denque >= 0.5",
-    "fork >= 0.2",
-    "metamodule >= 0.4",
-    "minheap >= 0.2",
-    "reco >= 1.6",
-    "epoll >= 0.5.0",
-    "kqueue >= 0.6.0",
-    "time-clock >= 0.4.0",
-    "time-sleep >= 0.2.1",
-    "waitpid >= 0.1.0",
+    "lauxhlib >= 0.6.3",
+    "denque >= 0.5.2",
+    "fork >= 0.4.2",
+    "metamodule >= 0.5.1",
+    "minheap >= 0.2.0",
+    "reco >= 1.6.1",
+    "epoll >= 0.6.0",
+    "kqueue >= 0.7.0",
+    "time-clock >= 0.5.2",
+    "time-sleep >= 0.2.3",
+    "waitpid >= 0.3.4",
+}
+build_dependencies = {
+    "luarocks-build-hooks >= 0.8.0",
 }
 build = {
-    type = "builtin",
+    type = "hooks",
+    before_build = {
+        "$(extra-vars)",
+    },
+    extra_variables = {
+        CFLAGS = "-Wall -Wno-trigraphs -Wmissing-field-initializers -Wreturn-type -Wmissing-braces -Wparentheses -Wno-switch -Wunused-function -Wunused-label -Wunused-parameter -Wunused-variable -Wunused-value -Wuninitialized -Wunknown-pragmas -Wshadow -Wsign-compare",
+    },
+    conditional_variables = {
+        ACT_COVERAGE = {
+            CFLAGS = "--coverage",
+            LIBFLAG = "--coverage",
+        },
+    },
     modules = {
         act = "act.lua",
         ["act.aux"] = "lib/aux.lua",
-        ["act.bitset"] = "src/bitset.c",
+        ["act.bitset"] = {
+            sources = "src/bitset.c",
+            incdirs = {
+                "src",
+                "$(DEP_LAUXHLIB_INCDIR)",
+            },
+        },
         ["act.callee"] = "lib/callee.lua",
         ["act.context"] = "lib/context.lua",
         ["act.coro"] = "lib/coro.lua",
@@ -42,6 +64,11 @@ build = {
         ["act.poller"] = "lib/poller.lua",
         ["act.pool"] = "lib/pool.lua",
         ["act.runq"] = "lib/runq.lua",
-        ["act.stack"] = "src/stack.c",
+        ["act.stack"] = {
+            sources = "src/stack.c",
+            incdirs = {
+                "$(DEP_LAUXHLIB_INCDIR)",
+            },
+        },
     },
 }
diff --git a/src/bitset.c b/src/bitset.c
index 714133b..50e631d 100644
--- a/src/bitset.c
+++ b/src/bitset.c
@@ -20,8 +20,14 @@
  *  IN THE SOFTWARE.
  */
 
+// project
 #include "bitset.h"
+// depend
 #include "lauxhlib.h"
+// lua
+#include <lauxlib.h>
+// system
+#include <string.h>
 
 #define MODULE_MT "act.bitset"
 
diff --git a/src/getcpus.c b/src/getcpus.c
index c19b3a1..98a17cf 100644
--- a/src/getcpus.c
+++ b/src/getcpus.c
@@ -19,9 +19,10 @@
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  * DEALINGS IN THE SOFTWARE.
  */
-#include <unistd.h>
 // lua
 #include <lua.h>
+// system
+#include <unistd.h>
 
 static int getcpus_lua(lua_State *L)
 {
diff --git a/src/ignsigpipe.c b/src/ignsigpipe.c
index 55d9fa2..f75ccba 100644
--- a/src/ignsigpipe.c
+++ b/src/ignsigpipe.c
@@ -22,9 +22,10 @@
  * this code copied from lua-nosigpipe
  */
 
-#include <signal.h>
-// lualib
+// lua
 #include <lauxlib.h>
+// system
+#include <signal.h>
 
 LUALIB_API int luaopen_act_ignsigpipe(lua_State *L)
 {
diff --git a/src/stack.c b/src/stack.c
index a919d3e..e0161b0 100644
--- a/src/stack.c
+++ b/src/stack.c
@@ -20,7 +20,10 @@
  *  IN THE SOFTWARE.
  */
 
+// depend
 #include "lauxhlib.h"
+// lua
+#include <lauxlib.h>
 
 #define MODULE_MT "act.stack"
 
@@ -89,7 +92,6 @@ static int set_lua(lua_State *L)
 {
     int argc       = lua_gettop(L) - 1;
     act_stack_t *s = luaL_checkudata(L, 1, MODULE_MT);
-    lua_Integer n  = 0;
 
     // clear arguments
     lua_settop(s->L, 0);
diff --git a/test/act_fork_waitpid_test.lua b/test/act_fork_waitpid_test.lua
index 739a9d4..13e5ea6 100644
--- a/test/act_fork_waitpid_test.lua
+++ b/test/act_fork_waitpid_test.lua
@@ -1,7 +1,6 @@
 local with_luacov = require('luacov').with_luacov
 local testcase = require('testcase')
 local getpid = require('testcase.getpid')
-local errno = require('errno')
 local act = require('act')
 local gettime = require('time.clock').gettime
 
@@ -123,11 +122,11 @@ function testcase.waitpid()
         return
     end
 
-    -- test that return error if no child process exists
+    -- test that return all nil if no child process exists
     assert(act.run(with_luacov(function()
         local res, err, timeout = act.waitpid()
         assert.is_nil(res)
-        assert.equal(err.type, errno.ECHILD)
+        assert.is_nil(err)
         assert.is_nil(timeout)
     end)))
 
diff --git a/test/bitset_test.lua b/test/bitset_test.lua
new file mode 100644
index 0000000..23dfb3e
--- /dev/null
+++ b/test/bitset_test.lua
@@ -0,0 +1,98 @@
+local testcase = require('testcase')
+local assert = require('assert')
+local bitset = require('act.bitset')
+
+function testcase.new_and_tostring()
+    local bs = bitset()
+    assert.match(tostring(bs), 'act.bitset: 0x', false)
+end
+
+function testcase.get_set_unset()
+    local bs = bitset()
+    -- initial value is 0
+    assert.is_false(bs:get(0))
+    assert.is_false(bs:get(100))
+    -- set then get returns 1
+    assert.is_true(bs:set(10))
+    assert.is_true(bs:get(10))
+    -- unset then get returns 0
+    assert.is_true(bs:unset(10))
+    assert.is_false(bs:get(10))
+end
+
+function testcase.set_resizes_when_pos_exceeds_capacity()
+    local bs = bitset()
+    -- initial capacity is 4096 bits, set beyond it triggers resize
+    assert.is_true(bs:set(8192))
+    assert.is_true(bs:get(8192))
+    assert.is_false(bs:get(8000))
+end
+
+function testcase.get_out_of_range_returns_error()
+    local bs = bitset()
+    -- get does not resize; out-of-range returns nil + ERANGE message
+    local v, err, errno = bs:get(1000000)
+    assert.is_nil(v)
+    assert.is_string(err)
+    assert.greater(errno, 0)
+end
+
+function testcase.unset_out_of_range_returns_error()
+    local bs = bitset()
+    -- unset does not resize; out-of-range returns nil + ERANGE message
+    local ok, err, errno = bs:unset(1000000)
+    assert.is_nil(ok)
+    assert.is_string(err)
+    assert.greater(errno, 0)
+end
+
+function testcase.ffz_empty_partial_full()
+    local bs = bitset()
+    -- empty: first zero is position 0
+    assert.equal(bs:ffz(), 0)
+    -- after setting bit 0, first zero is 1
+    bs:set(0)
+    assert.equal(bs:ffz(), 1)
+    -- after setting bit 1, first zero is 2
+    bs:set(1)
+    assert.equal(bs:ffz(), 2)
+end
+
+function testcase.ffz_returns_capacity_when_full()
+    local bs = bitset()
+    for pos = 0, 4095 do
+        bs:set(pos)
+    end
+    -- when bitset is fully set, ffz reports nbit (no zero bit found)
+    assert.equal(bs:ffz(), 4096)
+end
+
+function testcase.add_returns_consecutive_positions()
+    local bs = bitset()
+    assert.equal(bs:add(), 0)
+    assert.equal(bs:add(), 1)
+    assert.equal(bs:add(), 2)
+    bs:unset(1)
+    -- next add reuses freed position
+    assert.equal(bs:add(), 1)
+    assert.equal(bs:add(), 3)
+end
+
+function testcase.add_grows_beyond_initial_capacity()
+    local bs = bitset()
+    -- exhaust initial capacity
+    for _ = 0, 4095 do
+        bs:add()
+    end
+    -- next add must trigger resize and succeed
+    assert.equal(bs:add(), 4096)
+    assert.is_true(bs:get(4096))
+end
+
+function testcase.gc_cleanup()
+    local bs = bitset()
+    bs:set(0)
+    bs = nil -- luacheck: ignore 311
+    collectgarbage('collect')
+    collectgarbage('collect')
+end
diff --git a/test/stack_test.lua b/test/stack_test.lua
new file mode 100644
index 0000000..b2a1157
--- /dev/null
+++ b/test/stack_test.lua
@@ -0,0 +1,129 @@
+local testcase = require('testcase')
+local assert = require('assert')
+local stack = require('act.stack')
+
+function testcase.new_empty_and_tostring()
+    local s = stack()
+    assert.match(tostring(s), 'act.stack: 0x', false)
+    assert.equal(#s, 0)
+end
+
+function testcase.new_with_initial_values()
+    local s = stack('a', 'b', 'c')
+    assert.equal(#s, 3)
+    -- values are taken in order; pop returns the last pushed
+    assert.equal(s:pop(), 'c')
+    assert.equal(s:pop(), 'b')
+    assert.equal(s:pop(), 'a')
+    assert.equal(#s, 0)
+end
+
+function testcase.push_pop()
+    local s = stack()
+    s:push('x', 'y', 'z')
+    assert.equal(#s, 3)
+    assert.equal(s:pop(), 'z')
+    assert.equal(s:pop(), 'y')
+    assert.equal(s:pop(), 'x')
+end
+
+function testcase.pop_when_empty_returns_nothing()
+    local s = stack()
+    assert.equal(select('#', s:pop()), 0)
+end
+
+function testcase.push_with_no_args_is_noop()
+    local s = stack('a')
+    s:push()
+    assert.equal(#s, 1)
+end
+
+function testcase.unshift_prepends_to_head()
+    local s = stack('b', 'c')
+    s:unshift('a0', 'a1')
+    -- head is now a0,a1,b,c -> pop yields c,b,a1,a0
+    assert.equal(s:pop(), 'c')
+    assert.equal(s:pop(), 'b')
+    assert.equal(s:pop(), 'a1')
+    assert.equal(s:pop(), 'a0')
+end
+
+function testcase.unshift_with_no_args_is_noop()
+    local s = stack('a', 'b')
+    s:unshift()
+    assert.equal(#s, 2)
+end
+
+function testcase.insert_at_head()
+    local s = stack('b', 'c')
+    -- idx <= 1 prepends
+    s:insert(1, 'a0', 'a1')
+    assert.equal(s:pop(), 'c')
+    assert.equal(s:pop(), 'b')
+    assert.equal(s:pop(), 'a1')
+    assert.equal(s:pop(), 'a0')
+end
+
+function testcase.insert_at_middle()
+    local s = stack('a', 'b', 'c', 'd')
+    -- insert at idx=2 within current length
+    s:insert(2, 'X', 'Y')
+    assert.equal(#s, 6)
+end
+
+function testcase.insert_beyond_length_appends()
+    local s = stack('a', 'b')
+    -- idx > tail and not <=1: extra args are still appended at the tail
+    s:insert(99, 'X')
+    assert.equal(#s, 3)
+    assert.equal(s:pop(), 'X')
+end
+
+function testcase.insert_with_no_extra_args_is_noop()
+    local s = stack('a', 'b')
+    s:insert(1)
+    assert.equal(#s, 2)
+end
+
+function testcase.set_replaces_contents()
+    local s = stack('a', 'b', 'c')
+    s:set('x', 'y')
+    assert.equal(#s, 2)
+    assert.equal(s:pop(), 'y')
+    assert.equal(s:pop(), 'x')
+end
+
+function testcase.set_with_no_args_clears()
+    local s = stack('a', 'b')
+    s:set()
+    assert.equal(#s, 0)
+end
+
+function testcase.clear_returns_all_values()
+    local s = stack('a', 'b', 'c')
+    local a, b, c = s:clear()
+    assert.equal(a, 'a')
+    assert.equal(b, 'b')
+    assert.equal(c, 'c')
+    assert.equal(#s, 0)
+end
+
+function testcase.clear_with_args_appends_then_returns_all()
+    local s = stack('a')
+    local a, b, c = s:clear('b', 'c')
+    assert.equal(a, 'a')
+    assert.equal(b, 'b')
+    assert.equal(c, 'c')
+    assert.equal(#s, 0)
+end
+
+function testcase.clear_when_empty_returns_nothing()
+    local s = stack()
+    assert.equal(select('#', s:clear()), 0)
+end
+
+function testcase.gc_cleanup()
+    stack('a', 'b', 'c')
+    collectgarbage('collect')
+    collectgarbage('collect')
+end