diff --git a/test/unit/fixtures/posix.h b/test/unit/fixtures/posix.h
new file mode 100644
index 0000000000..f6f24cd9dc
--- /dev/null
+++ b/test/unit/fixtures/posix.h
@@ -0,0 +1,11 @@
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+
+enum {
+  kPOSIXErrnoEINTR = EINTR,
+  kPOSIXErrnoECHILD = ECHILD,
+  kPOSIXWaitWUNTRACED = WUNTRACED,
+};
diff --git a/test/unit/helpers.lua b/test/unit/helpers.lua
index 20fdf6f85d..832cbcbd4a 100644
--- a/test/unit/helpers.lua
+++ b/test/unit/helpers.lua
@@ -238,7 +238,7 @@ if posix ~= nil then
     wait = posix.wait,
     exit = posix._exit,
   }
-else
+elseif syscall ~= nil then
   sc = {
     fork = syscall.fork,
     pipe = function()
@@ -257,6 +257,90 @@ else
     wait = syscall.wait,
     exit = syscall.exit,
   }
+else
+  cimport('./test/unit/fixtures/posix.h')
+  sc = {
+    fork = function()
+      return tonumber(ffi.C.fork())
+    end,
+    pipe = function()
+      local ret = ffi.new('int[2]', {-1, -1})
+      ffi.errno(0)
+      local res = ffi.C.pipe(ret)
+      if (res ~= 0) then
+        local err = ffi.errno(0)
+        assert(res == 0, ("pipe() error: %u: %s"):format(
+            err, ffi.string(ffi.C.strerror(err))))
+      end
+      assert(ret[0] ~= -1 and ret[1] ~= -1)
+      return ret[0], ret[1]
+    end,
+    read = function(rd, len)
+      local ret = ffi.new('char[?]', len, {0})
+      local total_bytes_read = 0
+      ffi.errno(0)
+      while total_bytes_read < len do
+        local bytes_read = tonumber(ffi.C.read(
+            rd,
+            ffi.cast('void*', ret + total_bytes_read),
+            len - total_bytes_read))
+        if bytes_read == -1 then
+          local err = ffi.errno(0)
+          if err ~= libnvim.kPOSIXErrnoEINTR then
+            assert(false, ("read() error: %u: %s"):format(
+                err, ffi.string(ffi.C.strerror(err))))
+          end
+        elseif bytes_read == 0 then
+          break
+        else
+          total_bytes_read = total_bytes_read + bytes_read
+        end
+      end
+      return ffi.string(ret, total_bytes_read)
+    end,
+    write = function(wr, s)
+      local wbuf = to_cstr(s)
+      local total_bytes_written = 0
+      ffi.errno(0)
+      while total_bytes_written < #s do
+        local bytes_written = tonumber(ffi.C.write(
+            wr,
+            ffi.cast('void*', wbuf + total_bytes_written),
+            #s - total_bytes_written))
+        if bytes_written == -1 then
+          local err = ffi.errno(0)
+          if err ~= libnvim.kPOSIXErrnoEINTR then
+            assert(false, ("write() error: %u: %s"):format(
+                err, ffi.string(ffi.C.strerror(err))))
+          end
+        elseif bytes_written == 0 then
+          break
+        else
+          total_bytes_written = total_bytes_written + bytes_written
+        end
+      end
+      return total_bytes_written
+    end,
+    close = ffi.C.close,
+    wait = function(pid)
+      ffi.errno(0)
+      while true do
+        local r = ffi.C.waitpid(pid, nil, libnvim.kPOSIXWaitWUNTRACED)
+        if r == -1 then
+          local err = ffi.errno(0)
+          if err == libnvim.kPOSIXErrnoECHILD then
+            break
+          elseif err ~= libnvim.kPOSIXErrnoEINTR then
+            assert(false, ("waitpid() error: %u: %s"):format(
+                err, ffi.string(ffi.C.strerror(err))))
+          end
+        else
+          assert(r == pid)
+        end
+      end
+    end,
+    exit = ffi.C._exit,
+  }
 end
 
 local function gen_itp(it)
diff --git a/third-party/cmake/BuildLuarocks.cmake b/third-party/cmake/BuildLuarocks.cmake
index 6ab87b9bc3..9ea96b7cc5 100644
--- a/third-party/cmake/BuildLuarocks.cmake
+++ b/third-party/cmake/BuildLuarocks.cmake
@@ -172,12 +172,5 @@ if(USE_BUNDLED_BUSTED)
   add_custom_target(nvim-client
     DEPENDS ${HOSTDEPS_LIB_DIR}/luarocks/rocks/nvim-client)
 
-  add_custom_command(OUTPUT ${HOSTDEPS_BIN_DIR}/luaposix
-    COMMAND ${LUAROCKS_BINARY}
-    ARGS build https://raw.githubusercontent.com/luaposix/luaposix/release-v33.4.0/luaposix-33.4.0-1.rockspec ${LUAROCKS_BUILDARGS}
-    DEPENDS luarocks)
-  add_custom_target(luaposix
-    DEPENDS ${HOSTDEPS_BIN_DIR}/luaposix)
-
-  list(APPEND THIRD_PARTY_DEPS busted luacheck nvim-client luaposix)
+  list(APPEND THIRD_PARTY_DEPS busted luacheck nvim-client)
 endif()