Simulate clock skew and time anomalies.

Provides a virtual clock that can be skewed forward or backward, useful for testing time-sensitive logic like TTLs, rate limiting, scheduling, and expiration handling.

Configuration

• :skew_ms - Amount to shift time by (positive = future, negative = past)
• :drift_rate - Clock drift rate (1.0 = normal, 1.1 = 10% fast, 0.9 = 10% slow)
• :duration_ms - How long the skew persists (default: 5000ms)
• :mode - :instant (jump) or :gradual (drift)

Virtual Clock

This nemesis provides a virtual clock via PropertyDamage.Nemesis.ClockSkew.now/0. Your adapter should use this instead of System.system_time/0 to be testable:

defmodule MyAdapter do
  def get_current_time do
    PropertyDamage.Nemesis.ClockSkew.now()
  end
end

Example

def commands do
  [
    {CreateSession, weight: 5},
    {CheckSessionExpiry, weight: 5},
    {PropertyDamage.Nemesis.ClockSkew, weight: 1}
  ]
end

Testing Behavior

With clock skew, your system should:

• Handle time going "backward" gracefully
• Not break when time jumps forward
• Tolerate clock drift between nodes