message: `InstanceId` no longer has to be passed in.
diff: @@ -562,7 +562,6 @@ struct HighwayTestHarnessBuilder<DS: DeliveryStrategy> {
  /// Type of discrete distribution of validators' weights.
  /// Defaults to uniform.
  weight_distribution: Distribution,
  - instance_id: <TestContext as Context>::InstanceId,
  /// Seed for `Highway`.
  /// Defaults to 0.
  seed: u64,
  @@ -591,7 +590,7 @@ impl DeliveryStrategy for InstantDeliveryNoDropping {
  }
  impl HighwayTestHarnessBuilder<InstantDeliveryNoDropping> {
  - fn new(instance_id: <TestContext as Context>::InstanceId) -> Self {
  + fn new() -> Self {
  HighwayTestHarnessBuilder {
  validators_secs: HashMap::new(),
  faulty_weight: 0,
  @@ -602,7 +601,6 @@ impl HighwayTestHarnessBuilder<InstantDeliveryNoDropping> {
  weight_limits: (0, 0),
  start_time: Timestamp::zero(),
  weight_distribution: Distribution::Uniform,
  - instance_id,
  seed: 0,
  round_exp: 12,
  }
  @@ -655,7 +653,6 @@ impl<DS: DeliveryStrategy> HighwayTestHarnessBuilder<DS> {
  weight_limits: self.weight_limits,
  start_time: self.start_time,
  weight_distribution: self.weight_distribution,
  - instance_id: self.instance_id,
  seed: self.seed,
  round_exp: self.round_exp,
  }
  @@ -703,7 +700,7 @@ impl<DS: DeliveryStrategy> HighwayTestHarnessBuilder<DS> {
  .clone()
  .ok_or_else(|| BuilderError::EmptyConsensusValues)?;
  - let instance_id = self.instance_id.clone();
  + let instance_id = 0;
  let seed = self.seed;
  let round_exp = self.round_exp;
  let start_time = self.start_time;
  @@ -954,11 +951,9 @@ mod test_harness {
  #[test]
  fn on_empty_queue_error() {
  let mut rand = XorShiftRng::from_seed(rand::random());
  - let validators = vec![(ValidatorId(0), TestSecret(0))].into_iter().collect();
  let mut highway_test_harness: HighwayTestHarness<InstantDeliveryNoDropping> =
  - HighwayTestHarnessBuilder::new(0u64)
  - .validators(validators)
  + HighwayTestHarnessBuilder::new()
  .consensus_values(vec![1])
  .weight_limits(7, 10)
  .build(&mut rand)
  @@ -977,13 +972,8 @@ mod test_harness {
  #[test]
  fn done_when_all_finalized() -> Result<(), TestRunError> {
  let mut rand = XorShiftRng::from_seed(rand::random());
  - let validators = (0..10u32)
  - .map(|i| (ValidatorId(i as u64), TestSecret(i)))
  - .collect();
  -
  let mut highway_test_harness: HighwayTestHarness<InstantDeliveryNoDropping> =
  - HighwayTestHarnessBuilder::new(0u64)
  - .validators(validators)
  + HighwayTestHarnessBuilder::new()
  .consensus_values((0..10).collect())
  .weight_limits(7, 10)
  .build(&mut rand)
  