1 files changed, 19 insertions, 7 deletions
diff --git a/test/mkmf/test_egrep_cpp.rb b/test/mkmf/test_egrep_cpp.rb
index ce276bef20..1126324965 100644
--- a/test/mkmf/test_egrep_cpp.rb
+++ b/test/mkmf/test_egrep_cpp.rb
@@ -2,14 +2,26 @@
 require_relative 'base'
 require 'tempfile'
 
-class TestMkmf
-  class TestEgrepCpp < TestMkmf
-    def test_egrep_cpp
-      assert_equal(true, egrep_cpp(/ruby_init/, ""), MKMFLOG)
-    end
+class TestMkmfEgrepCpp < TestMkmf
+  def test_egrep_cpp
+    assert_equal(true, egrep_cpp(/ruby_init/, ""), MKMFLOG)
+  end
+
+  def test_not_have_func
+    assert_equal(false, egrep_cpp(/never match/, ""), MKMFLOG)
+  end
 
-    def test_not_have_func
-      assert_equal(false, egrep_cpp(/never match/, ""), MKMFLOG)
+  class TestMkmfEgrepCxx < self
+    def test_cxx_egrep_cpp
+      assert_equal(true, MakeMakefile["C++"].egrep_cpp(/^ok/, <<~SRC), MKMFLOG)
+      #ifdef __cplusplus
+      ok
+      #else
+      #error not C++
+      #endif
+      SRC
+    rescue Errno::ENOENT
+      omit "C++ compiler not available: #{$!.message}"
     end
   end
 end