Failing "Test PIPE" in test 182 in 2.64

[Stepan Kasal]

Hello,
  I observed a test failure with Autoconf 2.64.
The failing code is located under the comment "Test PIPE" in
autotest.at.
iIn the command below that comment, micro-suite seems to exit with
exit code 0.
The check below fails as this is not allowed.

Please give me some hints how I could debug this.

Thanks,
        Stepan