From 9b08aca878557bf390cf8322b28ce069d41a5e3f Mon Sep 17 00:00:00 2001
From: Ben Burkert <ben@benburkert.com>
Date: Mon, 31 Aug 2026 09:30:25 -0400
Subject: [PATCH] Assert testing.{Reader,Writer}Indirect initialized with
 non-zero buffer

Both std.testing.ReaderIndirect & std.testing.WriterIndirect require a
non-zero length buffer because their purpose is to exercise internal
buffering, not to be a pass-through Reader/Writer. Asserting a non-zero
buffer length prevents unintended behavior like infinite loops on
certain operations.
---
 lib/std/testing.zig | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/std/testing.zig b/lib/std/testing.zig
index d7ee376afb152587681de2ea8875c2c653a72f2e..53c52b71073a80a1360ca4d9bd39b9e2d603eb1d 100644
--- a/lib/std/testing.zig
+++ b/lib/std/testing.zig
@@ -1306,11 +1306,14 @@ pub const Reader = struct {
 
 /// A `Io.Reader` that gets its data from another `Io.Reader`, and always
 /// writes to its own buffer (and returns 0) during `stream` and `readVec`.
+/// Note: zero length buffers are not supported.
 pub const ReaderIndirect = struct {
     in: *Io.Reader,
     interface: Io.Reader,
 
     pub fn init(in: *Io.Reader, buffer: []u8) ReaderIndirect {
+        assert(buffer.len > 0);
+
         return .{
             .in = in,
             .interface = .{
@@ -1366,11 +1369,14 @@ pub const ReaderIndirect = struct {
 
 /// A `Io.Writer` that writes its data to another `Io.Writer`, and only
 /// writes new data to its own buffer during `drain`.
+/// Note: zero length buffers are not supported.
 pub const WriterIndirect = struct {
     out: *Io.Writer,
     interface: Io.Writer,
 
     pub fn init(out: *Io.Writer, buffer: []u8) WriterIndirect {
+        assert(buffer.len > 0);
+
         return .{
             .out = out,
             .interface = .{
-- 
2.54.0