diff --git a/test/io.c b/test/io.c
new file mode 100644
index 0000000..9cdf31a
--- /dev/null
+++ b/test/io.c
@@ -0,0 +1,35 @@
+#include "io.h"
+
+char buf[65536];
+int64 readpos = 0;
+int64 writepos = 0;
+int flageof = 0;
+
+int main()
+{
+  int64 r;
+
+  if (!io_fd(0)) return 111;
+  if (!io_fd(1)) return 111;
+
+  for (;;) {
+    if (flageof && writepos >= readpos) return 0;
+
+    if (!flageof && readpos < sizeof buf) {
+      r = io_tryread(0,buf + readpos,sizeof buf - readpos);
+      if (r <= -2) return 111; /* read error other than EAGAIN */
+      if (r == 0) flageof = 1;
+      if (r > 0) readpos += r;
+    }
+
+    if (writepos < readpos) {
+      r = io_trywrite(1,buf + writepos,readpos - writepos);
+      if (r <= -2) return 111; /* write error other than EAGAIN */
+      if (r > 0) {
+	writepos += r;
+	if (writepos == readpos) readpos = writepos = 0;
+	/* if writepos is big, might want to left-shift buffer here */
+      }
+    }
+  }
+}
diff --git a/test/io2.c b/test/io2.c
new file mode 100644
index 0000000..36dc1cf
--- /dev/null
+++ b/test/io2.c
@@ -0,0 +1,41 @@
+#include "io.h"
+
+char buf[65536];
+int64 readpos = 0;
+int64 writepos = 0;
+int flageof = 0;
+
+int main()
+{
+  int64 r;
+
+  if (!io_fd(0)) return 111;
+  if (!io_fd(1)) return 111;
+
+  for (;;) {
+    if (flageof && writepos >= readpos) return 0;
+
+    if (!flageof && readpos < sizeof buf) io_wantread(0);
+    if (writepos < readpos) io_wantwrite(1);
+    io_wait();
+    if (!flageof && readpos < sizeof buf) io_dontwantread(0);
+    if (writepos < readpos) io_dontwantwrite(1);
+
+    if (!flageof && readpos < sizeof buf) {
+      r = io_tryread(0,buf + readpos,sizeof buf - readpos);
+      if (r <= -2) return 111; /* read error other than EAGAIN */
+      if (r == 0) flageof = 1;
+      if (r > 0) readpos += r;
+    }
+
+    if (writepos < readpos) {
+      r = io_trywrite(1,buf + writepos,readpos - writepos);
+      if (r <= -2) return 111; /* write error other than EAGAIN */
+      if (r > 0) {
+	writepos += r;
+	if (writepos == readpos) readpos = writepos = 0;
+	/* if writepos is big, might want to left-shift buffer here */
+      }
+    }
+  }
+}