title: Q# unit testing to check phase
body: <p>I want to test a phase oracle by testing if the phase of qubit flipped.
  I tried to do it by</p>
  <pre><code>AssertQubitIsInStateWithinTolerance((Complex(0., 0.), Complex(-1., 0.)), qubit, 1e-5);
  </code></pre>
  <p>But it doesn't really check the phase because the same input also worked for the test without phase</p>
  <pre><code>AssertQubitIsInStateWithinTolerance((Complex(0., 0.), Complex(1., 0.)), qubit, 1e-5);
  </code></pre>
  <p>Is there a way to use unit tests to check the phase of qubit (or of the entire register)?</p>
  <p>Thanks for the help.</p>