@ParameterizedTest
    @NullSource
    @ValueSource(strings = { "", " ", "simple", "with unicode Ω≈ç√", "long-0123456789-abcdefghijklmnopqrstuvwxyz" })
    @DisplayName("Message-only ctor: propagates message and unsuccessful status")
    void messageOnlyConstructor_setsMessage_andUnsuccessfulStatus(String msg) {
        // Arrange & Act

    testMarkAndReset(TransferKind.END_OF_STREAM)
  }

  private fun testMarkAndReset(transferKind: TransferKind) {
    val builder = MockResponse.Builder()
    transferKind.setBody(builder, "ABCDEFGHIJKLMNOPQRSTUVWXYZ", 1024)
    server.enqueue(builder.build())
    server.enqueue(builder.build())
    val inputStream = getResponse(newRequest("/")).body.byteStream()

		t.Fatal("ReadByte at EOF: got no error")
	}
	if err := b.UnreadByte(); err == nil {
		t.Fatal("UnreadByte after ReadByte at EOF: got no error")
	}

	// check not at EOF
	b.WriteString("abcdefghijklmnopqrstuvwxyz")

	// after unsuccessful read
	if n, err := b.Read(nil); n != 0 || err != nil {
		t.Fatalf("Read(nil) = %d,%v; want 0,nil", n, err)
	}
	if err := b.UnreadByte(); err == nil {