private static String debugStringEqualityAssertionFailure(byte[] actual, byte[] expected) {
    final String pythonStyleMultilineHorizontalRule = "\"\"\"";
    return String.format(
        "synchronously-drained publisher (len=%d) has different contents than expected"
            + " publication (len=%d); force-stringifying both for inspection:\n"
            + "ACTUAL byte buffer (printed as if UTF8 string):\n%s\n%s\n%s\n"
            + "EXPECTED byte buffer (printed as if UTF8 string):\n%s\n%s\n%s\n",
        actual.length,
        expected.length,

        // expected block
        pythonStyleMultilineHorizontalRule,
        new String(actual, UTF_8),
        pythonStyleMultilineHorizontalRule,

        // expected block
        pythonStyleMultilineHorizontalRule,
        new String(expected, UTF_8),
        pythonStyleMultilineHorizontalRule);
  }
Simplifies JDK 11 APIs that don't provide testing utilities to drain a {@link Flow.Publisher} for
easy test-assertions.

<p>Designed to be used solely via {@link FakeSynchronousSubscriber#assertPublishes}.
extensions/data-transfer/portability-data-transfer-apple/src/test/java/org/datatransferproject/datatransfer/apple/http/FakeSynchronousSubscriber.java