diff --git a/lib/cmdtest/testcase.rb b/lib/cmdtest/testcase.rb
index 230c17d..2d4b41e 100644
--- a/lib/cmdtest/testcase.rb
+++ b/lib/cmdtest/testcase.rb
@@ -66,7 +66,7 @@ module Cmdtest
 
     ORIG_CWD = Dir.pwd
 
-    attr_reader :_work_dir, :_env
+    attr_reader :_work_dir, :_env_setenv
 
     def initialize(test_method, clog, runner)
       @_test_method = test_method
@@ -74,7 +74,7 @@ module Cmdtest
       @_runner = runner
       @_work_dir = Workdir.new(self, runner)
       @_cwd = @_runner.tmp_work_dir
-      @_env = Hash.new
+      @_env_setenv = Hash.new
       @_in_cmd = false
       @_comment_str = nil
       @_env_path = @_runner.orig_env_path
@@ -198,13 +198,13 @@ module Cmdtest
     #------------------------------
 
     def setenv(name, value)
-      @_env[name] = value
+      @_env_setenv[name] = [:setenv, value]
     end
 
     #------------------------------
 
     def unsetenv(name)
-      @_env.delete(name)
+      @_env_setenv[name] = [:unsetenv]
     end
 
     #------------------------------
diff --git a/lib/cmdtest/workdir.rb b/lib/cmdtest/workdir.rb
index 61dcb32..77ad44f 100644
--- a/lib/cmdtest/workdir.rb
+++ b/lib/cmdtest/workdir.rb
@@ -94,7 +94,17 @@ module Cmdtest
 
     def _ENV_strs(env)
       # TODO: windows
-      env.keys.sort.map {|k| "export %s='%s'" % [k, env[k]] }
+      env.keys.sort.map do |k|
+        what = env[k][0]
+        case what
+        when :setenv
+          "export %s='%s'" % [k, env[k][1]]
+        when :unsetenv
+          "unset %s" % [k]
+        else
+          raise "internal error"
+        end
+      end
     end
 
     def _chdir_str(dir)
@@ -139,7 +149,7 @@ module Cmdtest
       end
 
       File.open(_tmp_redirect_sh, "w") do |f|
-        f.puts _ENV_strs(@testcase._env)
+        f.puts _ENV_strs(@testcase._env_setenv)
         f.puts
         f.puts _chdir_str(@testcase._cwd)
         f.puts
diff --git a/t/CMDTEST_setenv.rb b/t/CMDTEST_setenv.rb
new file mode 100644
index 0000000..e27d560
--- /dev/null
+++ b/t/CMDTEST_setenv.rb
@@ -0,0 +1,83 @@
+require "selftest_utils"
+
+class CMDTEST_setenv < Cmdtest::Testcase
+
+  include SelftestUtils
+
+  #-----------------------------------
+
+  def test_setenv
+    #----------
+    create_CMDTEST_foo [
+      'cmd "env | grep TESTVAR1" do',
+      '  exit_nonzero', # no match in grep
+      'end',
+    ]
+    cmd_cmdtest do
+      comment "TESTVAR1 not set"
+      stdout_equal [
+        "### env | grep TESTVAR1",
+      ]
+    end
+
+    #----------
+    create_CMDTEST_foo [
+      'setenv "TESTVAR1", "123456"',
+      'cmd "env | grep TESTVAR1" do',
+      '  stdout_equal "TESTVAR1=123456\\n"',
+      'end',
+    ]
+    cmd_cmdtest do
+      comment "TESTVAR1 set by setenv"
+      stdout_equal [
+        "### env | grep TESTVAR1",
+      ]
+    end
+
+    cmd("env | grep TESTVAR1") do
+      comment "TESTVAR1 still unset on level1"
+      exit_nonzero # no match in grep
+    end
+  end
+
+  #-----------------------------------
+
+  def test_unsetenv
+    ENV['TESTVAR2'] = '987654'
+    #----------
+    create_CMDTEST_foo [
+      'cmd "env | grep TESTVAR2" do',
+      '  stdout_equal "TESTVAR2=987654\\n"',
+      'end',
+    ]
+    cmd_cmdtest do
+      comment "TESTVAR2 set from start"
+      stdout_equal [
+        "### env | grep TESTVAR2",
+      ]
+    end
+
+    #----------
+    create_CMDTEST_foo [
+      'unsetenv "TESTVAR2"',
+      'cmd "env | grep TESTVAR2" do',
+      '  exit_nonzero', # no match in grep
+      'end',
+    ]
+    cmd_cmdtest do
+      comment "TESTVAR2 unset by unsetenv"
+      stdout_equal [
+        "### env | grep TESTVAR2",
+      ]
+    end
+
+    cmd("env | grep TESTVAR2") do
+      comment "TESTVAR2 still set on level1"
+      stdout_equal [
+        "TESTVAR2=987654",
+      ]
+    end
+  end
+
+end
+