Auto merge of #100539 - joboet:horizon_timeout_clock, r=thomcc

[rust.git] / library / std / src / io / buffered / tests.rs

diff --git a/library/std/src/io/buffered/tests.rs b/library/std/src/io/buffered/tests.rs
index bd6d95242ad94e4b04bfda9951c624da84a2ef23..f4e688eb926cc7bff8962f1f79ecca455d7c27bc 100644 (file)
--- a/library/std/src/io/buffered/tests.rs
+++ b/library/std/src/io/buffered/tests.rs
@@ -1039,3 +1039,27 @@ fn single_formatted_write() {
     writeln!(&mut writer, "{}, {}!", "hello", "world").unwrap();
     assert_eq!(writer.get_ref().events, [RecordedEvent::Write("hello, world!\n".to_string())]);
 }
+
+#[test]
+fn bufreader_full_initialize() {
+    struct OneByteReader;
+    impl Read for OneByteReader {
+        fn read(&mut self, buf: &mut [u8]) -> crate::io::Result<usize> {
+            if buf.len() > 0 {
+                buf[0] = 0;
+                Ok(1)
+            } else {
+                Ok(0)
+            }
+        }
+    }
+    let mut reader = BufReader::new(OneByteReader);
+    // Nothing is initialized yet.
+    assert_eq!(reader.initialized(), 0);
+
+    let buf = reader.fill_buf().unwrap();
+    // We read one byte...
+    assert_eq!(buf.len(), 1);
+    // But we initialized the whole buffer!
+    assert_eq!(reader.initialized(), reader.capacity());
+}