diff --git a/test/str/cat.cpp b/test/str/cat.cpp
index ef958ea..a61800f 100644
--- a/test/str/cat.cpp
+++ b/test/str/cat.cpp
@@ -1,3 +1,4 @@
+#include <stdplus/str/buf.hpp>
 #include <stdplus/str/cat.hpp>
 #include <stdplus/zstring_view.hpp>
 
@@ -34,4 +35,13 @@
     EXPECT_EQ("func world", strCat("func"s, " world"));
 }
 
+TEST(StrAppend, Buf)
+{
+    StrBuf buf;
+    strAppend(buf, "a ");
+    strAppend(buf);
+    strAppend(buf, "b"s, " c"sv);
+    EXPECT_EQ("a b c", buf);
+}
+
 } // namespace stdplus