diff --git a/lib/ruby_wasm/build.rb b/lib/ruby_wasm/build.rb
index 437b0550d3..3d6e8c9bf4 100644
--- a/lib/ruby_wasm/build.rb
+++ b/lib/ruby_wasm/build.rb
@@ -3,4 +3,34 @@
 require_relative "build/toolchain"
 
 module RubyWasm
+  # Build executor to run the actual build commands.
+  class BuildExecutor
+    def system(*args, **kwargs)
+      Kernel.system(*args, **kwargs)
+    end
+
+    def rm_rf(list)
+      FileUtils.rm_rf(list)
+    end
+
+    def rm_f(list)
+      FileUtils.rm_f(list)
+    end
+
+    def cp_r(src, dest)
+      FileUtils.cp_r(src, dest)
+    end
+
+    def mv(src, dest)
+      FileUtils.mv(src, dest)
+    end
+
+    def mkdir_p(list)
+      FileUtils.mkdir_p(list)
+    end
+
+    def write(path, data)
+      File.write(path, data)
+    end
+  end
 end
diff --git a/lib/ruby_wasm/build/product/baseruby.rb b/lib/ruby_wasm/build/product/baseruby.rb
index 72d8fb1cc9..d2fc7baec7 100644
--- a/lib/ruby_wasm/build/product/baseruby.rb
+++ b/lib/ruby_wasm/build/product/baseruby.rb
@@ -20,13 +20,13 @@ def name
       "baseruby-#{@channel}"
     end
 
-    def build
-      FileUtils.mkdir_p product_build_dir
-      @source.build
+    def build(executor)
+      executor.mkdir_p product_build_dir
+      @source.build(executor)
       return if Dir.exist?(install_dir)
       Dir.chdir(product_build_dir) do
-        system "#{@source.configure_file} --prefix=#{install_dir} --disable-install-doc"
-        system "make install"
+        executor.system "#{@source.configure_file} --prefix=#{install_dir} --disable-install-doc"
+        executor.system "make install"
       end
     end
   end
diff --git a/lib/ruby_wasm/build/product/crossruby.rb b/lib/ruby_wasm/build/product/crossruby.rb
index 48bdf7b04a..b0511d0801 100644
--- a/lib/ruby_wasm/build/product/crossruby.rb
+++ b/lib/ruby_wasm/build/product/crossruby.rb
@@ -27,19 +27,22 @@ def make_args(crossruby)
       make_args
     end
 
-    def build(crossruby)
+    def build(executor, crossruby)
       lib = @name
       objdir = product_build_dir crossruby
-      FileUtils.mkdir_p objdir
-      do_extconf crossruby
-      system %Q(make -C "#{objdir}" #{make_args(crossruby).join(" ")} #{lib}.a)
+      executor.mkdir_p objdir
+      do_extconf executor, crossruby
+      executor.system %Q(make -C "#{objdir}" #{make_args(crossruby).join(" ")} #{lib}.a)
       # A ext can provide link args by link.filelist. It contains only built archive file by default.
       unless File.exist?(linklist(crossruby))
-        File.write(linklist(crossruby), Dir.glob("#{objdir}/*.a").join("\n"))
+        executor.write(
+          linklist(crossruby),
+          Dir.glob("#{objdir}/*.a").join("\n")
+        )
       end
     end
 
-    def do_extconf(crossruby)
+    def do_extconf(executor, crossruby)
       objdir = product_build_dir crossruby
       source = crossruby.source
       extconf_args = [
@@ -63,14 +66,14 @@ def do_extconf(crossruby)
         "-I#{crossruby.build_dir}"
       ]
       # Clear RUBYOPT to avoid loading unrelated bundle setup
-      system ({ "RUBYOPT" => "" }),
-             "#{crossruby.baseruby_path} #{extconf_args.join(" ")}",
-             chdir: objdir
+      executor.system ({ "RUBYOPT" => "" }),
+                      "#{crossruby.baseruby_path} #{extconf_args.join(" ")}",
+                      chdir: objdir
     end
 
-    def do_install_rb(crossruby)
+    def do_install_rb(executor, crossruby)
       objdir = product_build_dir crossruby
-      system %Q(make -C "#{objdir}" #{make_args(crossruby).join(" ")} install-rb)
+      executor.system %Q(make -C "#{objdir}" #{make_args(crossruby).join(" ")} install-rb)
     end
 
     def cache_key(digest)
@@ -123,45 +126,48 @@ def initialize(
       super(@params.target, @toolchain)
     end
 
-    def configure(reconfigure: false)
+    def configure(executor, reconfigure: false)
       if !File.exist?("#{build_dir}/Makefile") || reconfigure
         args = configure_args(RbConfig::CONFIG["host"], toolchain)
-        system "#{source.configure_file} #{args.join(" ")}", chdir: build_dir
+        executor.system "#{source.configure_file} #{args.join(" ")}",
+                        chdir: build_dir
       end
       # NOTE: we need rbconfig.rb at configuration time to build user given extensions with mkmf
-      system "make rbconfig.rb", chdir: build_dir
+      executor.system "make rbconfig.rb", chdir: build_dir
     end
 
-    def build_exts
-      @user_exts.each { |prod| prod.build(self) }
-      FileUtils.mkdir_p File.dirname(extinit_obj)
-      system %Q(ruby #{extinit_c_erb} #{@user_exts.map(&:name).join(" ")} | #{toolchain.cc} -c -x c - -o #{extinit_obj})
+    def build_exts(executor)
+      @user_exts.each { |prod| prod.build(executor, self) }
+      executor.mkdir_p File.dirname(extinit_obj)
+      executor.system %Q(ruby #{extinit_c_erb} #{@user_exts.map(&:name).join(" ")} | #{toolchain.cc} -c -x c - -o #{extinit_obj})
     end
 
-    def build(remake: false, reconfigure: false)
-      FileUtils.mkdir_p dest_dir
-      FileUtils.mkdir_p build_dir
+    def build(executor, remake: false, reconfigure: false)
+      executor.mkdir_p dest_dir
+      executor.mkdir_p build_dir
       @toolchain.install
-      [@source, @baseruby, @libyaml, @zlib, @openssl, @wasi_vfs].each(&:build)
-      configure(reconfigure: reconfigure)
-      build_exts
+      [@source, @baseruby, @libyaml, @zlib, @openssl, @wasi_vfs].each do |prod|
+        prod.build(executor)
+      end
+      configure(executor, reconfigure: reconfigure)
+      build_exts(executor)
 
       install_dir = File.join(build_dir, "install")
       if !File.exist?(install_dir) || remake || reconfigure
-        system "make install DESTDIR=#{install_dir}", chdir: build_dir
+        executor.system "make install DESTDIR=#{install_dir}", chdir: build_dir
       end
 
-      FileUtils.rm_rf dest_dir
-      FileUtils.cp_r install_dir, dest_dir
-      @user_exts.each { |ext| ext.do_install_rb(self) }
-      system "tar cfz #{artifact} -C rubies #{name}"
+      executor.rm_rf dest_dir
+      executor.cp_r install_dir, dest_dir
+      @user_exts.each { |ext| ext.do_install_rb(executor, self) }
+      executor.system "tar cfz #{artifact} -C rubies #{name}"
     end
 
-    def clean
-      FileUtils.rm_rf dest_dir
-      FileUtils.rm_rf build_dir
-      FileUtils.rm_rf ext_build_dir
-      FileUtils.rm_f artifact
+    def clean(executor)
+      executor.rm_rf dest_dir
+      executor.rm_rf build_dir
+      executor.rm_rf ext_build_dir
+      executor.rm_f artifact
     end
 
     def name
diff --git a/lib/ruby_wasm/build/product/libyaml.rb b/lib/ruby_wasm/build/product/libyaml.rb
index efe781ed0b..6d8c588d37 100644
--- a/lib/ruby_wasm/build/product/libyaml.rb
+++ b/lib/ruby_wasm/build/product/libyaml.rb
@@ -28,20 +28,22 @@ def name
       product_build_dir
     end
 
-    def build
+    def build(executor)
       return if Dir.exist?(install_root)
 
-      FileUtils.mkdir_p File.dirname(product_build_dir)
-      FileUtils.rm_rf product_build_dir
-      system "curl -L https://github.com/yaml/libyaml/releases/download/#{LIBYAML_VERSION}/yaml-#{LIBYAML_VERSION}.tar.gz | tar xz",
-             chdir: File.dirname(product_build_dir)
+      executor.mkdir_p File.dirname(product_build_dir)
+      executor.rm_rf product_build_dir
+      executor.system "curl -L https://github.com/yaml/libyaml/releases/download/#{LIBYAML_VERSION}/yaml-#{LIBYAML_VERSION}.tar.gz | tar xz",
+                      chdir: File.dirname(product_build_dir)
 
       # obtain the latest config.guess and config.sub for Emscripten and WASI triple support
-      system "curl -o #{product_build_dir}/config/config.guess 'https://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD'"
-      system "curl -o #{product_build_dir}/config/config.sub 'https://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD'"
+      executor.system "curl -o #{product_build_dir}/config/config.guess 'https://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD'"
+      executor.system "curl -o #{product_build_dir}/config/config.sub 'https://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD'"
 
-      system "./configure #{configure_args.join(" ")}", chdir: product_build_dir
-      system "make install DESTDIR=#{destdir}", chdir: product_build_dir
+      executor.system "./configure #{configure_args.join(" ")}",
+                      chdir: product_build_dir
+      executor.system "make install DESTDIR=#{destdir}",
+                      chdir: product_build_dir
     end
   end
 end
diff --git a/lib/ruby_wasm/build/product/openssl.rb b/lib/ruby_wasm/build/product/openssl.rb
index 160ad7c907..f653293e54 100644
--- a/lib/ruby_wasm/build/product/openssl.rb
+++ b/lib/ruby_wasm/build/product/openssl.rb
@@ -54,18 +54,20 @@ def configure_args
       args + tools_args
     end
 
-    def build
+    def build(executor)
       return if Dir.exist?(install_root)
 
-      FileUtils.mkdir_p File.dirname(product_build_dir)
-      FileUtils.rm_rf product_build_dir
-      system "curl -L https://www.openssl.org/source/openssl-#{OPENSSL_VERSION}.tar.gz | tar xz",
-             chdir: File.dirname(product_build_dir)
+      executor.mkdir_p File.dirname(product_build_dir)
+      executor.rm_rf product_build_dir
+      executor.system "curl -L https://www.openssl.org/source/openssl-#{OPENSSL_VERSION}.tar.gz | tar xz",
+                      chdir: File.dirname(product_build_dir)
 
-      system "./Configure #{configure_args.join(" ")}", chdir: product_build_dir
+      executor.system "./Configure #{configure_args.join(" ")}",
+                      chdir: product_build_dir
       # Use "install_sw" instead of "install" because it tries to install docs and it's very slow.
       # OpenSSL build system doesn't have well support for parallel build, so force -j1.
-      system "make -j1 install_sw DESTDIR=#{destdir}", chdir: product_build_dir
+      executor.system "make -j1 install_sw DESTDIR=#{destdir}",
+                      chdir: product_build_dir
     end
   end
 end
diff --git a/lib/ruby_wasm/build/product/ruby_source.rb b/lib/ruby_wasm/build/product/ruby_source.rb
index 4c59db7953..4d582c774b 100644
--- a/lib/ruby_wasm/build/product/ruby_source.rb
+++ b/lib/ruby_wasm/build/product/ruby_source.rb
@@ -31,37 +31,39 @@ def configure_file
       File.join(src_dir, "configure")
     end
 
-    def fetch
+    def fetch(executor)
       case @params[:type]
       when "github"
         repo_url = "https://github.com/#{@params[:repo]}.git"
-        FileUtils.mkdir_p src_dir
-        system "git init", chdir: src_dir
-        system "git remote add origin #{repo_url}", chdir: src_dir
-        system(
+        executor.mkdir_p src_dir
+        executor.system "git init", chdir: src_dir
+        executor.system "git remote add origin #{repo_url}", chdir: src_dir
+        executor.system(
           "git fetch --depth 1 origin #{@params[:rev]}:origin/#{@params[:rev]}",
           chdir: src_dir
         ) or raise "failed to clone #{repo_url}"
-        system("git checkout origin/#{@params[:rev]}", chdir: src_dir) or
-          raise "failed to checkout #{@params[:rev]}"
+        executor.system(
+          "git checkout origin/#{@params[:rev]}",
+          chdir: src_dir
+        ) or raise "failed to checkout #{@params[:rev]}"
       when "local"
-        FileUtils.mkdir_p File.dirname(src_dir)
-        FileUtils.cp_r @params[:src], src_dir
+        executor.mkdir_p File.dirname(src_dir)
+        executor.cp_r @params[:src], src_dir
       else
         raise "unknown source type: #{@params[:type]}"
       end
       (@params[:patches] || []).each do |patch_path|
-        system "patch -p1 < #{patch_path}", chdir: src_dir
+        executor.system "patch -p1 < #{patch_path}", chdir: src_dir
       end
     end
 
-    def build
-      fetch unless File.exist?(src_dir)
+    def build(executor)
+      fetch(executor) unless File.exist?(src_dir)
       unless File.exist?(configure_file)
         Dir.chdir(src_dir) do
-          system "ruby tool/downloader.rb -d tool -e gnu config.guess config.sub" or
+          executor.system "ruby tool/downloader.rb -d tool -e gnu config.guess config.sub" or
             raise "failed to download config.guess and config.sub"
-          system "./autogen.sh" or raise "failed to run autogen.sh"
+          executor.system "./autogen.sh" or raise "failed to run autogen.sh"
         end
       end
     end
diff --git a/lib/ruby_wasm/build/product/wasi_vfs.rb b/lib/ruby_wasm/build/product/wasi_vfs.rb
index 62eacde4e6..3ca22a4ed0 100644
--- a/lib/ruby_wasm/build/product/wasi_vfs.rb
+++ b/lib/ruby_wasm/build/product/wasi_vfs.rb
@@ -40,16 +40,16 @@ def name
       lib_product_build_dir
     end
 
-    def build
+    def build(executor)
       return if !@need_fetch_lib || File.exist?(lib_wasi_vfs_a)
       require "tmpdir"
       lib_wasi_vfs_url =
         "https://github.com/kateinoigakukun/wasi-vfs/releases/download/v#{WASI_VFS_VERSION}/libwasi_vfs-wasm32-unknown-unknown.zip"
       Dir.mktmpdir do |tmpdir|
-        system "curl -L #{lib_wasi_vfs_url} -o #{tmpdir}/libwasi_vfs.zip"
-        system "unzip #{tmpdir}/libwasi_vfs.zip -d #{tmpdir}"
-        FileUtils.mkdir_p File.dirname(lib_wasi_vfs_a)
-        FileUtils.mv File.join(tmpdir, "libwasi_vfs.a"), lib_wasi_vfs_a
+        executor.system "curl -L #{lib_wasi_vfs_url} -o #{tmpdir}/libwasi_vfs.zip"
+        executor.system "unzip #{tmpdir}/libwasi_vfs.zip -d #{tmpdir}"
+        executor.mkdir_p File.dirname(lib_wasi_vfs_a)
+        executor.mv File.join(tmpdir, "libwasi_vfs.a"), lib_wasi_vfs_a
       end
     end
 
diff --git a/lib/ruby_wasm/build/product/zlib.rb b/lib/ruby_wasm/build/product/zlib.rb
index 427cb03415..9b27b5ef13 100644
--- a/lib/ruby_wasm/build/product/zlib.rb
+++ b/lib/ruby_wasm/build/product/zlib.rb
@@ -34,19 +34,20 @@ def configure_args
       args + tools_args
     end
 
-    def build
+    def build(executor)
       return if Dir.exist?(install_root)
 
-      FileUtils.mkdir_p File.dirname(product_build_dir)
-      FileUtils.rm_rf product_build_dir
+      executor.mkdir_p File.dirname(product_build_dir)
+      executor.rm_rf product_build_dir
 
-      system "curl -L https://zlib.net/zlib-#{ZLIB_VERSION}.tar.gz | tar xz",
-             chdir: File.dirname(product_build_dir),
-             exception: true
+      executor.system "curl -L https://zlib.net/zlib-#{ZLIB_VERSION}.tar.gz | tar xz",
+                      chdir: File.dirname(product_build_dir),
+                      exception: true
 
-      system "#{configure_args.join(" ")} ./configure --static",
-             chdir: product_build_dir
-      system "make install DESTDIR=#{destdir}", chdir: product_build_dir
+      executor.system "#{configure_args.join(" ")} ./configure --static",
+                      chdir: product_build_dir
+      executor.system "make install DESTDIR=#{destdir}",
+                      chdir: product_build_dir
     end
   end
 end
diff --git a/lib/ruby_wasm/rake_task.rb b/lib/ruby_wasm/rake_task.rb
index e08f8fc9bb..62c2b06793 100644
--- a/lib/ruby_wasm/rake_task.rb
+++ b/lib/ruby_wasm/rake_task.rb
@@ -71,20 +71,22 @@ def initialize(
     @crossruby.with_wasi_vfs @wasi_vfs
     @crossruby.with_openssl @openssl
 
+    executor = RubyWasm::BuildExecutor.new
+
     desc "Cross-build Ruby for #{@target}"
     task name do
       next if File.exist? @crossruby.artifact
-      @crossruby.build
+      @crossruby.build(executor)
     end
     namespace name do
       task :remake do
-        @crossruby.build(remake: true)
+        @crossruby.build(executor, remake: true)
       end
       task :reconfigure do
-        @crossruby.build(reconfigure: true)
+        @crossruby.build(executor, reconfigure: true)
       end
       task :clean do
-        @crossruby.clean
+        @crossruby.clean(executor)
       end
     end
   end