Improve test

Author: nordlow

source/mir/appender.d

@@ -245,6 +245,9 @@ struct ScopedBuffer(T, size_t bytes = 4096)
         }
     }
 
+    ///
+    alias opOpAssign(string op : "~") = put;
+
     ///
     void reset() scope nothrow
     {
@@ -326,6 +329,23 @@ version (mir_test) unittest
     assert(buf.data == "cs");
 }
 
+@safe pure nothrow @nogc
+version (mir_test) unittest
+{
+    alias T = char;
+    const n = 3;
+    auto buf = scopedBuffer!(T, n * T.sizeof);
+    assert(buf._scopeBuffer.length == n); // stack
+    buf.reserve(n + 1);                   // transition to heap
+    assert(buf._buffer.length >= n + 1); // heap
+    buf ~= 'c';
+    buf ~= "str";
+    assert(buf.data == "cstr");
+
+    buf.popBackN(2);
+    assert(buf.data == "cs");
+}
+
 ///
 struct UnsafeArrayBuffer(T)
 {