diff --git a/lib/trinity/scheduler.ex b/lib/trinity/scheduler.ex
index a7a2ca4..4e487e9 100644
--- a/lib/trinity/scheduler.ex
+++ b/lib/trinity/scheduler.ex
@@ -48,10 +48,6 @@ defmodule Trinity.Scheduler do
   @spec get_sim :: Simulation.t
   defp get_sim, do: Process.get(simulation_key())
 
-  def run_simulation(fun) do
-    SimulationSupervisor.run_simulation(fun)
-  end
-
   @spec now :: integer
   def now do
     %{now: now} = get_sim()
diff --git a/lib/trinity/scheduler/simulation_supervisor.ex b/lib/trinity/scheduler/simulation_supervisor.ex
index 4f5e9f6..eaa0a07 100644
--- a/lib/trinity/scheduler/simulation_supervisor.ex
+++ b/lib/trinity/scheduler/simulation_supervisor.ex
@@ -15,10 +15,11 @@ defmodule Trinity.Scheduler.SimulationSupervisor do
     defstruct @enforce_keys
   end
 
-  @spec run_simulation(function) :: :ok
-  def run_simulation(fun) do
+  @spec run_simulation(function, %{seed: integer}) :: :ok
+  def run_simulation(fun, %{seed: seed}) do
     ref = make_ref()
     GenServer.start_link(__MODULE__, %{
+      seed: seed,
       fun: fun,
       parent_pid: self(),
       parent_ref: ref,
@@ -37,8 +38,9 @@ defmodule Trinity.Scheduler.SimulationSupervisor do
     GenServer.call(server, {:spawn_child, fun})
   end
 
-  def init(%{fun: fun, parent_pid: parent_pid, parent_ref: parent_ref}) do
+  def init(%{seed: seed, fun: fun, parent_pid: parent_pid, parent_ref: parent_ref}) do
     Process.flag(:trap_exit, true)
+    :rand.seed(:exsss, seed)
 
     sim = %Simulation{
       queue: :ets.new(__MODULE__, [:ordered_set, :public]),
@@ -148,7 +150,10 @@ defmodule Trinity.Scheduler.SimulationSupervisor do
   end
 
   defp spawn_sim_child(%Simulation{} = sim, fun) do
+    # TODO: larger range?
+    child_seed = Enum.random(1..1_000_000)
     spawn_link(fn ->
+      :rand.seed(:exsss, child_seed)
       Process.put(simulation_key(), sim)
       fun.()
     end)
diff --git a/lib/trinity/sim.ex b/lib/trinity/sim.ex
index 2862f67..b3739c7 100644
--- a/lib/trinity/sim.ex
+++ b/lib/trinity/sim.ex
@@ -5,6 +5,12 @@ defmodule Trinity.Sim do
   @spec get_sim :: Simulation.t | nil
   defp get_sim, do: Process.get(simulation_key())
 
+  @spec run_simulation(function, keyword) :: :ok
+  def run_simulation(fun, opts \\ []) do
+    seed = Keyword.get(opts, :seed, 100)
+    Trinity.Scheduler.SimulationSupervisor.run_simulation(fun, %{seed: seed})
+  end
+
   @spec simulated? :: boolean
   def simulated? do
     case get_sim() do
diff --git a/test/trinity_test.exs b/test/trinity_test.exs
index 2c9a0e5..60bd16c 100644
--- a/test/trinity_test.exs
+++ b/test/trinity_test.exs
@@ -1,7 +1,7 @@
 defmodule TrinityTest do
   use ExUnit.Case
 
-  alias Trinity.{SimProcess, SimLogger, Scheduler}
+  alias Trinity.{Sim, SimProcess, SimLogger, Scheduler}
   import Trinity.Scheduler, only: [receive_yield: 1]
   require SimLogger
 
@@ -53,7 +53,7 @@ defmodule TrinityTest do
   end
 
   test "scheduler" do
-    Scheduler.run_simulation(fn ->
+    Sim.run_simulation(fn ->
       nodes = [:n1, :n2, :n3]
       pids =
         Enum.map(nodes, fn node ->
@@ -98,6 +98,6 @@ defmodule TrinityTest do
 
       Scheduler.yield(1000)
       #dbg Scheduler.dump(), limit: :infinity
-    end)
+    end, seed: 101)
   end
 end