assertFailsWith<IllegalArgumentException> {
      Request.Builder().addHeader("a\tb", "c")
    }.also { expected ->
      assertThat(expected.message).isEqualTo("Unexpected char 0x09 at 1 in header name: a\tb")
    }
  }

  @Test
  fun responseHeaderNameWithSpacePermitted() {
    server.enqueue(
      MockResponse.Builder()
        .clearHeaders()

Tokens form the vocabulary of the Go language.
There are four classes: <i>identifiers</i>, <i>keywords</i>, <i>operators
and punctuation</i>, and <i>literals</i>.  <i>White space</i>, formed from
spaces (U+0020), horizontal tabs (U+0009),
carriage returns (U+000D), and newlines (U+000A),
is ignored except as it separates tokens
that would otherwise combine into a single token. Also, a newline or end of file