message: Added a check for variance data in child buffers
  The variance and exp-val info is populated in two different passes, making sure the data is consistent.
diff: @@ -169,6 +169,10 @@ TEST(VQETester, checkChildBuffers) {
  if (childBuff->name() != "I") {
  // has pauli-variance info.
  EXPECT_TRUE(childBuff->hasExtraInfoKey("pauli-variance"));
  + const double pauliVar = (*childBuff)["pauli-variance"].as<double>();
  + const double expVal = (*childBuff)["exp-val-z"].as<double>();
  + // Check buffer data mapping.
  + EXPECT_NEAR(pauliVar, 1.0 - expVal * expVal, 1e-6);
  }
  }
  }
  