diff --git a/pyphare/pyphare/pharein/simulation.py b/pyphare/pyphare/pharein/simulation.py
index 97ed32615..ee15a0b77 100644
--- a/pyphare/pyphare/pharein/simulation.py
+++ b/pyphare/pyphare/pharein/simulation.py
@@ -498,7 +498,7 @@ def check_diag_options(**kwargs):
                 diag_options["options"]["dir"], "diagnostics"
             )
         valid_modes = ["overwrite"]
-        if "mode" in diag_options["options"]:
+        if "options" in diag_options and "mode" in diag_options["options"]:
             mode = diag_options["options"]["mode"]
             if mode not in valid_modes:
                 raise ValueError(
diff --git a/tests/functional/harris/CMakeLists.txt b/tests/functional/harris/CMakeLists.txt
index afaf7b4d8..1cbb8723f 100644
--- a/tests/functional/harris/CMakeLists.txt
+++ b/tests/functional/harris/CMakeLists.txt
@@ -8,10 +8,14 @@ if(NOT ${PHARE_PROJECT_DIR} STREQUAL ${CMAKE_BINARY_DIR})
 endif()
 
 if(HighFive AND testMPI)
+
   ## These test use dump diagnostics so require HighFive!
-  # exec level 11
-  # mpirun -n 10
+
   if(testMPI)
-    phare_mpi_python3_exec(11 10 harris_2d harris_2d.py ${CMAKE_CURRENT_BINARY_DIR})
+
+    phare_mpi_python3_exec(11 4 harris_2d_100_x_100 harris_2d_100_x_100.py ${CMAKE_CURRENT_BINARY_DIR})
+    phare_mpi_python3_exec(11 4 harris_2d_100_x_100_slow harris_2d_100_x_100_slow.py ${CMAKE_CURRENT_BINARY_DIR})
+
   endif(testMPI)
+
 endif()
diff --git a/tests/functional/harris/harris_2d.py b/tests/functional/harris/harris_2d.py
index b9f06ced4..9ffd88576 100644
--- a/tests/functional/harris/harris_2d.py
+++ b/tests/functional/harris/harris_2d.py
@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-import os
+
 import numpy as np
 
 import pyphare.pharein as ph
@@ -7,34 +7,28 @@
 from pyphare.simulator.simulator import Simulator
 from pyphare.simulator.simulator import startMPI
 
-os.environ["PHARE_SCOPE_TIMING"] = "1"  # turn on scope timing
-"""
-  For scope timings to work
-  The env var PHARE_SCOPE_TIMING must be == "1" (or "true")
-    See src/phare/phare.hpp
-  CMake must be configured with: -DwithPhlop=ON
-  And a LOG_LEVEL must be defined via compile args: -DPHARE_LOG_LEVEL=1
-  Or change the default value in src/core/logger.hpp
-  And phlop must be available on PYTHONPATH either from subprojects
-   or install phlop via pip
-"""
-
 
 ph.NO_GUI()
 cpp = cpp_lib()
-startMPI()
+
+
 
 diag_outputs = "phare_outputs/test/harris/2d"
 time_step_nbr = 1000
 time_step = 0.001
 final_time = time_step * time_step_nbr
-dt = 10 * time_step
-nt = final_time / dt + 1
-timestamps = dt * np.arange(nt)
 
 
-def config():
-    sim = ph.Simulation(
+def default_timestamps():
+    dt = 10 * time_step
+    nt = final_time / dt + 1
+    timestamps = dt * np.arange(nt)
+
+
+def default_setup():
+    startMPI()
+
+    return ph.Simulation(
         smallest_patch_size=15,
         largest_patch_size=25,
         time_step_nbr=time_step_nbr,
@@ -53,6 +47,13 @@ def config():
         strict=True,
     )
 
+
+def config(sim = None, timestamps = None, seed = 12334):
+    if sim is None:
+        sim = default_setup()
+    if timestamps is None:
+        timestamps = default_timestamps()
+
     def density(x, y):
         L = sim.simulation_domain()[1]
         return (
@@ -141,7 +142,7 @@ def vthz(x, y):
         bx=bx,
         by=by,
         bz=bz,
-        protons={"charge": 1, "density": density, **vvv, "init": {"seed": 12334}},
+        protons={"charge": 1, "density": density, **vvv, "init": {"seed": seed}},
     )
 
     ph.ElectronModel(closure="isothermal", Te=0.0)
@@ -155,13 +156,7 @@ def vthz(x, y):
 
 def main():
     Simulator(config()).run()
-    try:
-        from tools.python3 import plotting as m_plotting
 
-        m_plotting.plot_run_timer_data(diag_outputs, cpp.mpi_rank())
-    except ImportError:
-        print("Phlop not found - install with: `pip install phlop`")
-    cpp.mpi_barrier()
 
 
 if __name__ == "__main__":
diff --git a/tests/functional/harris/harris_2d_lb.py b/tests/functional/harris/harris_2d_100_x_100.py
similarity index 54%
rename from tests/functional/harris/harris_2d_lb.py
rename to tests/functional/harris/harris_2d_100_x_100.py
index 1153b6e8b..ecc6cdbb1 100644
--- a/tests/functional/harris/harris_2d_lb.py
+++ b/tests/functional/harris/harris_2d_100_x_100.py
@@ -11,42 +11,46 @@
 from pyphare.simulator.simulator import Simulator, startMPI
 
 from tests.simulator import SimulatorTest
-from tools.python3 import plotting as m_plotting
+
+import harris_2d as base
 
 mpl.use("Agg")
 
-SCOPE_TIMING = os.getenv("PHARE_SCOPE_TIMING", "True").lower() in ("true", "1", "t")
+SCOPE_TIMING = os.getenv("PHARE_SCOPE_TIMING", "False").lower() in ("true", "1", "t")
+"""
+  For scope timings to work
+  The env var PHARE_SCOPE_TIMING must be == "1" (or "true")
+    See src/phare/phare.hpp
+  CMake must be configured with: -DwithPhlop=ON
+  And a LOG_LEVEL must be defined via compile args: -DPHARE_LOG_LEVEL=1
+  Or change the default value in src/core/logger.hpp
+  And phlop must be available on PYTHONPATH either from subprojects
+   or install phlop via pip
+"""
+
 LOAD_BALANCE = os.getenv("LOAD_BALANCE", "True").lower() in ("true", "1", "t")
 
 cpp = cpp_lib()
 startMPI()
 
-cells = (800, 800)
-time_step = 0.005
+cells = (100, 100)
 final_time = 50
+time_step = 0.005
 timestamps = np.arange(0, final_time + time_step, final_time / 5)
 
-if cpp.mpi_rank() == 0:
-    print(LOAD_BALANCE, "diag timestamps:", timestamps)
-
-diag_dir = "phare_outputs/harris_lb"
-if not LOAD_BALANCE:
-    diag_dir = "phare_outputs/harris"
-
+diag_dir = "phare_outputs/harris_2d_100_x_100"
 plot_dir = Path(f"{diag_dir}_plots")
 plot_dir.mkdir(parents=True, exist_ok=True)
 
 
 def config():
-    L = 0.5
-
     sim = ph.Simulation(
         time_step=time_step,
         final_time=final_time,
         cells=cells,
         dl=(0.40, 0.40),
-        refinement="tagging",
-        max_nbr_levels=2,
+        # refinement="tagging",
+        # max_nbr_levels=1,
         nesting_buffer=1,
         clustering="tile",
         tag_buffer="1",
@@ -56,91 +60,16 @@ def config():
             "format": "phareh5",
             "options": {"dir": diag_dir, "mode": "overwrite"},
         },
-        restart_options={
-            "dir": "checkpoints",
-            "mode": "overwrite",
-            "timestamps": timestamps,
-            # "restart_time": 0.0,
-        },
     )
 
-    def density(x, y):
-        Ly = sim.simulation_domain()[1]
-        return (
-            0.4
-            + 1.0 / np.cosh((y - Ly * 0.3) / L) ** 2
-            + 1.0 / np.cosh((y - Ly * 0.7) / L) ** 2
-        )
-
-    def S(y, y0, l):
-        return 0.5 * (1.0 + np.tanh((y - y0) / l))
-
-    def by(x, y):
-        Lx = sim.simulation_domain()[0]
-        Ly = sim.simulation_domain()[1]
-        sigma = 1.0
-        dB = 0.1
-
-        x0 = x - 0.5 * Lx
-        y1 = y - 0.3 * Ly
-        y2 = y - 0.7 * Ly
-
-        dBy1 = 2 * dB * x0 * np.exp(-(x0**2 + y1**2) / (sigma) ** 2)
-        dBy2 = -2 * dB * x0 * np.exp(-(x0**2 + y2**2) / (sigma) ** 2)
-
-        return dBy1 + dBy2
-
-    def bx(x, y):
-        Lx = sim.simulation_domain()[0]
-        Ly = sim.simulation_domain()[1]
-        sigma = 1.0
-        dB = 0.1
+    sim = base.config(sim, timestamps)
 
-        x0 = x - 0.5 * Lx
-        y1 = y - 0.3 * Ly
-        y2 = y - 0.7 * Ly
-
-        dBx1 = -2 * dB * y1 * np.exp(-(x0**2 + y1**2) / (sigma) ** 2)
-        dBx2 = 2 * dB * y2 * np.exp(-(x0**2 + y2**2) / (sigma) ** 2)
-
-        v1 = -1
-        v2 = 1.0
-        return v1 + (v2 - v1) * (S(y, Ly * 0.3, L) - S(y, Ly * 0.7, L)) + dBx1 + dBx2
-
-    def bz(x, y):
-        return 0.0
-
-    def b2(x, y):
-        return bx(x, y) ** 2 + by(x, y) ** 2 + bz(x, y) ** 2
-
-    def T(x, y):
-        K = 0.7
-        temp = 1.0 / density(x, y) * (K - b2(x, y) * 0.5)
-        assert np.all(temp > 0)
-        return temp
-
-    def vxyz(x, y):
-        return 0.0
-
-    def vthxyz(x, y):
-        return np.sqrt(T(x, y))
-
-    vvv = {**{f"vbulk{c}": vxyz for c in "xyz"}, **{f"vth{c}": vthxyz for c in "xyz"}}
-
-    ph.MaxwellianFluidModel(
-        bx=bx, by=by, bz=bz, protons={"charge": 1, "density": density, **vvv}
-    )
-    ph.ElectronModel(closure="isothermal", Te=0.0)
-
-    for quantity in ["E", "B"]:
-        ph.ElectromagDiagnostics(quantity=quantity, write_timestamps=timestamps)
     for quantity in ["density", "bulkVelocity"]:
         ph.FluidDiagnostics(quantity=quantity, write_timestamps=timestamps)
 
     ph.FluidDiagnostics(
         quantity="density", write_timestamps=timestamps, population_name="protons"
     )
-    ph.InfoDiagnostics(quantity="particle_count")
 
     if LOAD_BALANCE:
         ph.LoadBalancer(active=True, auto=True, mode="nppc", tol=0.05)
@@ -201,8 +130,15 @@ def test_run(self):
         Simulator(config()).run().reset()
         if cpp.mpi_rank() == 0:
             plot(diag_dir)
+
         if SCOPE_TIMING:
-            m_plotting.plot_run_timer_data(diag_dir, cpp.mpi_rank())
+            try:
+                from tools.python3 import plotting as m_plotting
+
+                m_plotting.plot_run_timer_data(diag_dir, cpp.mpi_rank())
+            except ImportError:
+                print("Phlop not found - install with: `pip install phlop`")
+
         cpp.mpi_barrier()
         return self
 
diff --git a/tests/functional/harris/harris_2d_100_x_100_slow.py b/tests/functional/harris/harris_2d_100_x_100_slow.py
new file mode 100644
index 000000000..cb744940c
--- /dev/null
+++ b/tests/functional/harris/harris_2d_100_x_100_slow.py
@@ -0,0 +1,147 @@
+#!/usr/bin/env python3
+
+import os
+import numpy as np
+import matplotlib as mpl
+from pathlib import Path
+
+import pyphare.pharein as ph
+from pyphare.cpp import cpp_lib
+from pyphare.pharesee.run import Run
+from pyphare.simulator.simulator import Simulator, startMPI
+
+from tests.simulator import SimulatorTest
+
+import harris_2d as base
+
+mpl.use("Agg")
+
+SCOPE_TIMING = os.getenv("PHARE_SCOPE_TIMING", "False").lower() in ("true", "1", "t")
+"""
+  For scope timings to work
+  The env var PHARE_SCOPE_TIMING must be == "1" (or "true")
+    See src/phare/phare.hpp
+  CMake must be configured with: -DwithPhlop=ON
+  And a LOG_LEVEL must be defined via compile args: -DPHARE_LOG_LEVEL=1
+  Or change the default value in src/core/logger.hpp
+  And phlop must be available on PYTHONPATH either from subprojects
+   or install phlop via pip
+"""
+
+LOAD_BALANCE = os.getenv("LOAD_BALANCE", "True").lower() in ("true", "1", "t")
+
+cpp = cpp_lib()
+startMPI()
+
+cells = (100, 100)
+final_time = 50
+time_step = 0.001
+timestamps = np.arange(0, final_time + time_step, final_time / 5)
+
+diag_dir = "phare_outputs/harris_2d_100_x_100_slow"
+plot_dir = Path(f"{diag_dir}_plots")
+plot_dir.mkdir(parents=True, exist_ok=True)
+
+
+def config():
+    sim = ph.Simulation(
+        time_step=time_step,
+        final_time=final_time,
+        cells=cells,
+        dl=(0.40, 0.40),
+        # refinement="tagging",
+        # max_nbr_levels=1,
+        nesting_buffer=1,
+        clustering="tile",
+        tag_buffer="1",
+        hyper_resistivity=0.002,
+        resistivity=0.001,
+        diag_options={
+            "format": "phareh5",
+            "options": {"dir": diag_dir, "mode": "overwrite"},
+        },
+    )
+
+    sim = base.config(sim, timestamps)
+
+    for quantity in ["density", "bulkVelocity"]:
+        ph.FluidDiagnostics(quantity=quantity, write_timestamps=timestamps)
+
+    ph.FluidDiagnostics(
+        quantity="density", write_timestamps=timestamps, population_name="protons"
+    )
+
+    if LOAD_BALANCE:
+        ph.LoadBalancer(active=True, auto=True, mode="nppc", tol=0.05)
+
+    return sim
+
+
+def plot_file_for_qty(qty, time):
+    return f"{plot_dir}/harris_{qty}_t{time}.png"
+
+
+def plot(diag_dir):
+    run = Run(diag_dir)
+    for time in timestamps:
+        run.GetDivB(time).plot(
+            filename=plot_file_for_qty("divb", time),
+            plot_patches=True,
+            vmin=1e-11,
+            vmax=2e-10,
+        )
+        run.GetRanks(time).plot(
+            filename=plot_file_for_qty("Ranks", time),
+            plot_patches=True,
+        )
+        run.GetN(time, pop_name="protons").plot(
+            filename=plot_file_for_qty("N", time),
+            plot_patches=True,
+        )
+        for c in ["x", "y", "z"]:
+            run.GetB(time).plot(
+                filename=plot_file_for_qty(f"b{c}", time),
+                qty=f"{c}",
+                plot_patches=True,
+            )
+        run.GetJ(time).plot(
+            filename=plot_file_for_qty("jz", time),
+            qty="z",
+            plot_patches=True,
+            vmin=-2,
+            vmax=2,
+        )
+
+
+class HarrisTest(SimulatorTest):
+    def __init__(self, *args, **kwargs):
+        super(HarrisTest, self).__init__(*args, **kwargs)
+        self.simulator = None
+
+    def tearDown(self):
+        super(HarrisTest, self).tearDown()
+        if self.simulator is not None:
+            self.simulator.reset()
+        self.simulator = None
+        ph.global_vars.sim = None
+
+    def test_run(self):
+        self.register_diag_dir_for_cleanup(diag_dir)
+        Simulator(config()).run().reset()
+        if cpp.mpi_rank() == 0:
+            plot(diag_dir)
+
+        if SCOPE_TIMING:
+            try:
+                from tools.python3 import plotting as m_plotting
+
+                m_plotting.plot_run_timer_data(diag_dir, cpp.mpi_rank())
+            except ImportError:
+                print("Phlop not found - install with: `pip install phlop`")
+
+        cpp.mpi_barrier()
+        return self
+
+
+if __name__ == "__main__":
+    HarrisTest().test_run().tearDown()
diff --git a/tests/simulator/CMakeLists.txt b/tests/simulator/CMakeLists.txt
index 86274d16f..edef7be5f 100644
--- a/tests/simulator/CMakeLists.txt
+++ b/tests/simulator/CMakeLists.txt
@@ -25,9 +25,12 @@ if(HighFive)
 
     # doesn't make sense in serial
     phare_mpi_python3_exec(9 3 load_balancing test_load_balancing.py ${CMAKE_CURRENT_BINARY_DIR})
-  endif(testMPI)
 
-  phare_python3_exec(11, test_diagnostic_timestamps test_diagnostic_timestamps.py ${CMAKE_CURRENT_BINARY_DIR})
+  else()
+    phare_python3_exec(11 test_diagnostic_timestamps test_diagnostic_timestamps.py ${CMAKE_CURRENT_BINARY_DIR})
+    
+  endif(testMPI)
+  
 endif()
 
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/config.py ${CMAKE_CURRENT_BINARY_DIR}/config.py @ONLY)
diff --git a/tests/simulator/refinement/CMakeLists.txt b/tests/simulator/refinement/CMakeLists.txt
index 178fc46e9..31772ce5d 100644
--- a/tests/simulator/refinement/CMakeLists.txt
+++ b/tests/simulator/refinement/CMakeLists.txt
@@ -10,7 +10,12 @@ endif()
 if(HighFive)
   ## These test use dump diagnostics so require HighFive!
   if(testMPI)
-    phare_mpi_python3_exec(9 2  simple_2d_refinement test_2d_2_core.py  ${CMAKE_CURRENT_BINARY_DIR})
-    phare_mpi_python3_exec(11 10 complex_2d_refinement test_2d_10_core.py  ${CMAKE_CURRENT_BINARY_DIR})
+
+    # disabled due to https://github.com/PHAREHUB/PHARE/issues/853
+    # phare_mpi_python3_exec(11 10 complex_2d_refinement test_2d_10_core.py  ${CMAKE_CURRENT_BINARY_DIR})
+
   endif(testMPI)
+
+  phare_python3_exec(9 simple_2d_refinement test_2d_2_core.py  ${CMAKE_CURRENT_BINARY_DIR})
+
 endif()