diff --git a/axelrod/deterministic_cache.py b/axelrod/deterministic_cache.py
index 8199f5ad2..4c2f0ee88 100644
--- a/axelrod/deterministic_cache.py
+++ b/axelrod/deterministic_cache.py
@@ -14,7 +14,7 @@
 
 import pickle
 from collections import UserDict
-from typing import List, Tuple
+from typing import List, Optional, Tuple
 
 from axelrod import Classifiers
 
@@ -104,7 +104,7 @@ class DeterministicCache(UserDict):
     methods to save/load the cache to/from a file.
     """
 
-    def __init__(self, file_name: str = None) -> None:
+    def __init__(self, file_name: Optional[str] = None) -> None:
         """Initialize a new cache.
 
         Parameters
diff --git a/axelrod/ecosystem.py b/axelrod/ecosystem.py
index aa2ad9a93..86f4fbd0d 100644
--- a/axelrod/ecosystem.py
+++ b/axelrod/ecosystem.py
@@ -12,7 +12,7 @@
 """
 
 import random
-from typing import Callable, List
+from typing import Callable, List, Optional
 
 from axelrod.result_set import ResultSet
 
@@ -29,8 +29,8 @@ class Ecosystem(object):
     def __init__(
         self,
         results: ResultSet,
-        fitness: Callable[[float], float] = None,
-        population: List[int] = None,
+        fitness: Optional[Callable[[float], float]] = None,
+        population: Optional[List[int]] = None,
     ) -> None:
         """Create a new ecosystem.
 
diff --git a/axelrod/fingerprint.py b/axelrod/fingerprint.py
index dec12ae05..140e88604 100644
--- a/axelrod/fingerprint.py
+++ b/axelrod/fingerprint.py
@@ -1,7 +1,7 @@
 import os
 from collections import namedtuple
 from tempfile import mkstemp
-from typing import Any, List, Union
+from typing import Any, List, Optional, Union
 
 import dask.dataframe as dd
 import matplotlib.pyplot as plt
@@ -280,10 +280,10 @@ def fingerprint(
         turns: int = 50,
         repetitions: int = 10,
         step: float = 0.01,
-        processes: int = None,
-        filename: str = None,
+        processes: Optional[int] = None,
+        filename: Optional[str] = None,
         progress_bar: bool = True,
-        seed: int = None,
+        seed: Optional[int] = None,
     ) -> dict:
         """Build and play the spatial tournament.
 
@@ -358,7 +358,7 @@ def plot(
         self,
         cmap: str = "seismic",
         interpolation: str = "none",
-        title: str = None,
+        title: Optional[str] = None,
         colorbar: bool = True,
         labels: bool = True,
     ) -> plt.Figure:
@@ -437,11 +437,11 @@ def fingerprint(
         self,
         turns: int = 50,
         repetitions: int = 1000,
-        noise: float = None,
-        processes: int = None,
-        filename: str = None,
+        noise: Optional[float] = None,
+        processes: Optional[int] = None,
+        filename: Optional[str] = None,
         progress_bar: bool = True,
-        seed: int = None,
+        seed: Optional[int] = None,
     ) -> np.ndarray:
         """Creates a spatial tournament to run the necessary matches to obtain
         fingerprint data.
@@ -556,7 +556,7 @@ def plot(
         self,
         cmap: str = "viridis",
         interpolation: str = "none",
-        title: str = None,
+        title: Optional[str] = None,
         colorbar: bool = True,
         labels: bool = True,
         display_names: bool = False,
diff --git a/axelrod/game.py b/axelrod/game.py
index 0d8f94380..c2b4ffc44 100644
--- a/axelrod/game.py
+++ b/axelrod/game.py
@@ -2,6 +2,7 @@
 from typing import Tuple, Union
 
 import numpy as np
+import numpy.typing as npt
 
 from axelrod import Action
 
@@ -20,7 +21,7 @@ class AsymmetricGame(object):
     """
 
     # pylint: disable=invalid-name
-    def __init__(self, A: np.array, B: np.array) -> None:
+    def __init__(self, A: npt.NDArray, B: npt.NDArray) -> None:
         """
         Creates an asymmetric game from two matrices.
 
diff --git a/axelrod/load_data_.py b/axelrod/load_data_.py
index e55f5f395..58ab40c46 100644
--- a/axelrod/load_data_.py
+++ b/axelrod/load_data_.py
@@ -1,6 +1,6 @@
 import pathlib
 import pkgutil
-from typing import Dict, List, Text, Tuple
+from typing import Callable, Dict, List, Optional, Tuple
 
 
 def axl_filename(path: pathlib.Path) -> pathlib.Path:
@@ -20,12 +20,18 @@ def axl_filename(path: pathlib.Path) -> pathlib.Path:
     return axl_path / path
 
 
-def load_file(filename: str, directory: str) -> List[List[str]]:
+def load_file(
+    filename: str,
+    directory: str,
+    get_data: Callable[[str, str], Optional[bytes]] = pkgutil.get_data,
+) -> List[List[str]]:
     """Loads a data file stored in the Axelrod library's data subdirectory,
     likely for parameters for a strategy."""
 
     path = str(pathlib.Path(directory) / filename)
-    data_bytes = pkgutil.get_data(__name__, path)
+    data_bytes = get_data(__name__, path)
+    if data_bytes is None:
+        raise FileNotFoundError(f"Some loader issue for path {path}")
     data = data_bytes.decode("UTF-8", "replace")
 
     rows = []
diff --git a/axelrod/mock_player.py b/axelrod/mock_player.py
index 41ee0de2a..c186c0c25 100644
--- a/axelrod/mock_player.py
+++ b/axelrod/mock_player.py
@@ -1,5 +1,5 @@
 from itertools import cycle
-from typing import List
+from typing import List, Optional
 
 from axelrod.action import Action
 from axelrod.player import Player
@@ -14,7 +14,7 @@ class MockPlayer(Player):
 
     name = "Mock Player"
 
-    def __init__(self, actions: List[Action] = None) -> None:
+    def __init__(self, actions: Optional[List[Action]] = None) -> None:
         super().__init__()
         if not actions:
             actions = []
diff --git a/axelrod/moran.py b/axelrod/moran.py
index b5e3ffbe8..539d3d5db 100644
--- a/axelrod/moran.py
+++ b/axelrod/moran.py
@@ -18,7 +18,7 @@ def __init__(
         self,
         players: List[Player],
         turns: int = DEFAULT_TURNS,
-        prob_end: float = None,
+        prob_end: Optional[float] = None,
         noise: float = 0,
         game: Game = None,
         deterministic_cache: DeterministicCache = None,
@@ -26,7 +26,7 @@ def __init__(
         mode: str = "bd",
         interaction_graph: Graph = None,
         reproduction_graph: Graph = None,
-        fitness_transformation: Callable = None,
+        fitness_transformation: Optional[Callable] = None,
         mutation_method="transition",
         stop_on_fixation=True,
         seed=None,
@@ -175,7 +175,7 @@ def set_players(self) -> None:
         self.populations = [self.population_distribution()]
 
     def fitness_proportionate_selection(
-        self, scores: List, fitness_transformation: Callable = None
+        self, scores: List, fitness_transformation: Optional[Callable] = None
     ) -> int:
         """Randomly selects an individual proportionally to score.
 
@@ -229,7 +229,7 @@ def mutate(self, index: int) -> Player:
         # Just clone the player
         return self.players[index].clone()
 
-    def death(self, index: int = None) -> int:
+    def death(self, index: Optional[int] = None) -> int:
         """
         Selects the player to be removed.
 
@@ -258,7 +258,7 @@ def death(self, index: int = None) -> int:
             i = self.index[vertex]
         return i
 
-    def birth(self, index: int = None) -> int:
+    def birth(self, index: Optional[int] = None) -> int:
         """The birth event.
 
         Parameters
@@ -349,7 +349,6 @@ def _matchup_indices(self) -> Set[Tuple[int, int]]:
         # The other calculations are unnecessary
         if self.mode == "db":
             source = self.index[self.dead]
-            self.dead = None
             sources = sorted(self.interaction_graph.out_vertices(source))
         else:
             # birth-death is global
diff --git a/axelrod/plot.py b/axelrod/plot.py
index 48509a1c7..23f5b7c9c 100644
--- a/axelrod/plot.py
+++ b/axelrod/plot.py
@@ -1,5 +1,5 @@
 import pathlib
-from typing import List, Union
+from typing import Any, Callable, List, Optional, Union
 
 import matplotlib
 import matplotlib.pyplot as plt
@@ -10,7 +10,7 @@
 from .load_data_ import axl_filename
 from .result_set import ResultSet
 
-titleType = List[str]
+titleType = str
 namesType = List[str]
 dataType = List[List[Union[int, float]]]
 
@@ -25,8 +25,11 @@ def _violinplot(
         self,
         data: dataType,
         names: namesType,
-        title: titleType = None,
-        ax: matplotlib.axes.SubplotBase = None,
+        title: Optional[titleType] = None,
+        ax: Optional[matplotlib.axes.Axes] = None,
+        get_figure: Callable[
+            [matplotlib.axes.Axes], Union[matplotlib.figure.Figure, Any, None]
+        ] = lambda ax: ax.get_figure(),
     ) -> matplotlib.figure.Figure:
         """For making violinplots."""
 
@@ -35,7 +38,11 @@ def _violinplot(
         else:
             ax = ax
 
-        figure = ax.get_figure()
+        figure = get_figure(ax)
+        if not isinstance(figure, matplotlib.figure.Figure):
+            raise RuntimeError(
+                "get_figure unexpectedly returned a non-figure object"
+            )
         width = max(self.num_players / 3, 12)
         height = width / 2
         spacing = 4
@@ -50,7 +57,7 @@ def _violinplot(
         )
         ax.set_xticks(positions)
         ax.set_xticklabels(names, rotation=90)
-        ax.set_xlim([0, spacing * (self.num_players + 1)])
+        ax.set_xlim((0, spacing * (self.num_players + 1)))
         ax.tick_params(axis="both", which="both", labelsize=8)
         if title:
             ax.set_title(title)
@@ -76,7 +83,9 @@ def _boxplot_xticks_labels(self):
         return [str(n) for n in self.result_set.ranked_names]
 
     def boxplot(
-        self, title: titleType = None, ax: matplotlib.axes.SubplotBase = None
+        self,
+        title: Optional[titleType] = None,
+        ax: Optional[matplotlib.axes.Axes] = None,
     ) -> matplotlib.figure.Figure:
         """For the specific mean score boxplot."""
         data = self._boxplot_dataset
@@ -98,7 +107,9 @@ def _winplot_dataset(self):
         return wins, ranked_names
 
     def winplot(
-        self, title: titleType = None, ax: matplotlib.axes.SubplotBase = None
+        self,
+        title: Optional[titleType] = None,
+        ax: Optional[matplotlib.axes.Axes] = None,
     ) -> matplotlib.figure.Figure:
         """Plots the distributions for the number of wins for each strategy."""
 
@@ -126,7 +137,9 @@ def _sdv_plot_dataset(self):
         return diffs, ranked_names
 
     def sdvplot(
-        self, title: titleType = None, ax: matplotlib.axes.SubplotBase = None
+        self,
+        title: Optional[titleType] = None,
+        ax: Optional[matplotlib.axes.Axes] = None,
     ) -> matplotlib.figure.Figure:
         """Score difference violin plots to visualize the distributions of how
         players attain their payoffs."""
@@ -143,7 +156,9 @@ def _lengthplot_dataset(self):
         ]
 
     def lengthplot(
-        self, title: titleType = None, ax: matplotlib.axes.SubplotBase = None
+        self,
+        title: Optional[titleType] = None,
+        ax: Optional[matplotlib.axes.Axes] = None,
     ) -> matplotlib.figure.Figure:
         """For the specific match length boxplot."""
         data = self._lengthplot_dataset
@@ -174,9 +189,12 @@ def _payoff_heatmap(
         self,
         data: dataType,
         names: namesType,
-        title: titleType = None,
-        ax: matplotlib.axes.SubplotBase = None,
+        title: Optional[titleType] = None,
+        ax: Optional[matplotlib.axes.Axes] = None,
         cmap: str = "viridis",
+        get_figure: Callable[
+            [matplotlib.axes.Axes], Union[matplotlib.figure.Figure, Any, None]
+        ] = lambda ax: ax.get_figure(),
     ) -> matplotlib.figure.Figure:
         """Generic heatmap plot"""
 
@@ -185,7 +203,11 @@ def _payoff_heatmap(
         else:
             ax = ax
 
-        figure = ax.get_figure()
+        figure = get_figure(ax)
+        if not isinstance(figure, matplotlib.figure.Figure):
+            raise RuntimeError(
+                "get_figure unexpectedly returned a non-figure object"
+            )
         width = max(self.num_players / 4, 12)
         height = width
         figure.set_size_inches(width, height)
@@ -202,7 +224,9 @@ def _payoff_heatmap(
         return figure
 
     def pdplot(
-        self, title: titleType = None, ax: matplotlib.axes.SubplotBase = None
+        self,
+        title: Optional[titleType] = None,
+        ax: Optional[matplotlib.axes.Axes] = None,
     ) -> matplotlib.figure.Figure:
         """Payoff difference heatmap to visualize the distributions of how
         players attain their payoffs."""
@@ -210,7 +234,9 @@ def pdplot(
         return self._payoff_heatmap(matrix, names, title=title, ax=ax)
 
     def payoff(
-        self, title: titleType = None, ax: matplotlib.axes.SubplotBase = None
+        self,
+        title: Optional[titleType] = None,
+        ax: Optional[matplotlib.axes.Axes] = None,
     ) -> matplotlib.figure.Figure:
         """Payoff heatmap to visualize the distributions of how
         players attain their payoffs."""
@@ -223,9 +249,12 @@ def payoff(
     def stackplot(
         self,
         eco,
-        title: titleType = None,
+        title: Optional[titleType] = None,
         logscale: bool = True,
-        ax: matplotlib.axes.SubplotBase = None,
+        ax: Optional[matplotlib.axes.Axes] = None,
+        get_figure: Callable[
+            [matplotlib.axes.Axes], Union[matplotlib.figure.Figure, Any, None]
+        ] = lambda ax: ax.get_figure(),
     ) -> matplotlib.figure.Figure:
 
         populations = eco.population_sizes
@@ -235,7 +264,11 @@ def stackplot(
         else:
             ax = ax
 
-        figure = ax.get_figure()
+        figure = get_figure(ax)
+        if not isinstance(figure, matplotlib.figure.Figure):
+            raise RuntimeError(
+                "get_figure unexpectedly returned a non-figure object"
+            )
         turns = range(len(populations))
         pops = [
             [populations[iturn][ir] for iturn in turns]
@@ -247,7 +280,7 @@ def stackplot(
         ax.yaxis.set_label_position("right")
         ax.yaxis.labelpad = 25.0
 
-        ax.set_ylim([0.0, 1.0])
+        ax.set_ylim((0.0, 1.0))
         ax.set_ylabel("Relative population size")
         ax.set_xlabel("Turn")
         if title is not None:
diff --git a/axelrod/strategies/adaptive.py b/axelrod/strategies/adaptive.py
index 5d7480565..039cf0d3f 100644
--- a/axelrod/strategies/adaptive.py
+++ b/axelrod/strategies/adaptive.py
@@ -1,4 +1,4 @@
-from typing import List
+from typing import List, Optional
 
 from axelrod.action import Action
 from axelrod.player import Player
@@ -26,7 +26,7 @@ class Adaptive(Player):
         "manipulates_state": False,
     }
 
-    def __init__(self, initial_plays: List[Action] = None) -> None:
+    def __init__(self, initial_plays: Optional[List[Action]] = None) -> None:
         super().__init__()
         if not initial_plays:
             initial_plays = [C] * 6 + [D] * 5
diff --git a/axelrod/strategies/ann.py b/axelrod/strategies/ann.py
index e7956450f..4fd764c67 100644
--- a/axelrod/strategies/ann.py
+++ b/axelrod/strategies/ann.py
@@ -1,4 +1,4 @@
-from typing import List, Tuple
+from typing import List, Optional, Tuple
 
 import numpy as np
 
@@ -198,7 +198,10 @@ class ANN(Player):
     }
 
     def __init__(
-        self, num_features: int, num_hidden: int, weights: List[float] = None
+        self,
+        num_features: int,
+        num_hidden: int,
+        weights: Optional[List[float]] = None,
     ) -> None:
         Player.__init__(self)
         self.num_features = num_features
@@ -236,10 +239,10 @@ def __init__(
         self,
         num_features: int,
         num_hidden: int,
-        weights: List[float] = None,
-        mutation_probability: float = None,
+        weights: Optional[List[float]] = None,
+        mutation_probability: Optional[float] = None,
         mutation_distance: int = 5,
-        seed: int = None,
+        seed: Optional[int] = None,
     ) -> None:
         EvolvablePlayer.__init__(self, seed=seed)
         (
diff --git a/axelrod/strategies/calculator.py b/axelrod/strategies/calculator.py
index 8b2546592..5d273a3ca 100644
--- a/axelrod/strategies/calculator.py
+++ b/axelrod/strategies/calculator.py
@@ -1,3 +1,5 @@
+from typing import Optional
+
 from axelrod._strategy_utils import detect_cycle
 from axelrod.action import Action
 from axelrod.player import Player
@@ -32,7 +34,7 @@ def __init__(self) -> None:
         self.joss_instance = Joss()
         super().__init__()
 
-    def set_seed(self, seed: int = None):
+    def set_seed(self, seed: Optional[int] = None):
         super().set_seed(seed)
         self.joss_instance.set_seed(seed)
 
diff --git a/axelrod/strategies/cycler.py b/axelrod/strategies/cycler.py
index ac2be686a..2eb27f206 100644
--- a/axelrod/strategies/cycler.py
+++ b/axelrod/strategies/cycler.py
@@ -1,6 +1,6 @@
 import copy
 import itertools
-from typing import List, Tuple
+from typing import List, Optional, Tuple
 
 from axelrod.action import Action, actions_to_str, str_to_actions
 from axelrod.evolvable_player import (
@@ -109,11 +109,11 @@ class EvolvableCycler(Cycler, EvolvablePlayer):
 
     def __init__(
         self,
-        cycle: str = None,
-        cycle_length: int = None,
+        cycle: Optional[str] = None,
+        cycle_length: Optional[int] = None,
         mutation_probability: float = 0.2,
         mutation_potency: int = 1,
-        seed: int = None,
+        seed: Optional[int] = None,
     ) -> None:
         EvolvablePlayer.__init__(self, seed=seed)
         cycle, cycle_length = self._normalize_parameters(cycle, cycle_length)
diff --git a/axelrod/strategies/finite_state_machines.py b/axelrod/strategies/finite_state_machines.py
index a20e408db..9dce23365 100644
--- a/axelrod/strategies/finite_state_machines.py
+++ b/axelrod/strategies/finite_state_machines.py
@@ -1,5 +1,5 @@
 import itertools
-from typing import Any, Dict, List, Sequence, Text, Tuple
+from typing import Any, Dict, List, Optional, Sequence, Text, Tuple
 
 from axelrod.action import Action
 from axelrod.evolvable_player import (
@@ -145,12 +145,12 @@ class EvolvableFSMPlayer(FSMPlayer, EvolvablePlayer):
 
     def __init__(
         self,
-        transitions: tuple = None,
-        initial_state: int = None,
+        transitions: Optional[tuple] = None,
+        initial_state: Optional[int] = None,
         initial_action: Action = None,
-        num_states: int = None,
+        num_states: Optional[int] = None,
         mutation_probability: float = 0.1,
-        seed: int = None,
+        seed: Optional[int] = None,
     ) -> None:
         """If transitions, initial_state, and initial_action are None
         then generate random parameters using num_states."""
@@ -189,10 +189,10 @@ def normalize_transitions(
 
     def _normalize_parameters(
         self,
-        transitions: Tuple = None,
-        initial_state: int = None,
+        transitions: Optional[Tuple] = None,
+        initial_state: Optional[int] = None,
         initial_action: Action = None,
-        num_states: int = None,
+        num_states: Optional[int] = None,
     ) -> Tuple[Tuple, int, Action, int]:
         if not (
             (transitions is not None)
diff --git a/axelrod/strategies/handshake.py b/axelrod/strategies/handshake.py
index 6e24ee1cd..fa248c78e 100644
--- a/axelrod/strategies/handshake.py
+++ b/axelrod/strategies/handshake.py
@@ -1,4 +1,4 @@
-from typing import List
+from typing import List, Optional
 
 from axelrod.action import Action
 from axelrod.player import Player
@@ -25,7 +25,7 @@ class Handshake(Player):
         "manipulates_state": False,
     }
 
-    def __init__(self, initial_plays: List[Action] = None) -> None:
+    def __init__(self, initial_plays: Optional[List[Action]] = None) -> None:
         super().__init__()
         if not initial_plays:
             initial_plays = [C, D]
diff --git a/axelrod/strategies/hmm.py b/axelrod/strategies/hmm.py
index 92038411e..f6989891a 100644
--- a/axelrod/strategies/hmm.py
+++ b/axelrod/strategies/hmm.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict
+from typing import Any, Dict, Optional
 
 from axelrod.action import Action
 from axelrod.evolvable_player import (
@@ -254,7 +254,7 @@ def __init__(
         initial_action=C,
         num_states=None,
         mutation_probability=None,
-        seed: int = None,
+        seed: Optional[int] = None,
     ) -> None:
         EvolvablePlayer.__init__(self, seed=seed)
         (
diff --git a/axelrod/strategies/memoryone.py b/axelrod/strategies/memoryone.py
index 22d33bfaa..6fe03c151 100644
--- a/axelrod/strategies/memoryone.py
+++ b/axelrod/strategies/memoryone.py
@@ -2,7 +2,7 @@
 files, including titfortat.py and zero_determinant.py"""
 
 import warnings
-from typing import Tuple
+from typing import Optional, Tuple
 
 from axelrod.action import Action
 from axelrod.player import Player
@@ -68,7 +68,7 @@ class MemoryOnePlayer(Player):
 
     def __init__(
         self,
-        four_vector: Tuple[float, float, float, float] = None,
+        four_vector: Optional[Tuple[float, float, float, float]] = None,
         initial: Action = C,
     ) -> None:
         """
@@ -179,7 +179,7 @@ class GTFT(MemoryOnePlayer):
         "manipulates_state": False,
     }
 
-    def __init__(self, p: float = None) -> None:
+    def __init__(self, p: Optional[float] = None) -> None:
         """
         Parameters
 
diff --git a/axelrod/strategies/prober.py b/axelrod/strategies/prober.py
index 78118a91c..c73d82c55 100644
--- a/axelrod/strategies/prober.py
+++ b/axelrod/strategies/prober.py
@@ -1,4 +1,4 @@
-from typing import List
+from typing import List, Optional
 
 from axelrod.action import Action
 from axelrod.player import Player
@@ -67,7 +67,7 @@ class Detective(Player):
         "manipulates_state": False,
     }
 
-    def __init__(self, initial_actions: List[Action] = None) -> None:
+    def __init__(self, initial_actions: Optional[List[Action]] = None) -> None:
         super().__init__()
         if initial_actions is None:
             self.initial_actions = [C, D, C, C]
diff --git a/axelrod/tests/unit/test_load_data.py b/axelrod/tests/unit/test_load_data.py
index 6dd880335..8273b1809 100644
--- a/axelrod/tests/unit/test_load_data.py
+++ b/axelrod/tests/unit/test_load_data.py
@@ -2,7 +2,7 @@
 import pathlib
 import unittest
 
-from axelrod.load_data_ import axl_filename
+from axelrod.load_data_ import axl_filename, load_file
 
 
 class TestLoadData(unittest.TestCase):
@@ -15,3 +15,15 @@ def test_axl_filename(self):
         expected_fn = os.path.join(dirname, "../../strategies/titfortat.py")
 
         self.assertTrue(os.path.samefile(actual_fn, expected_fn))
+
+    def test_raise_error_if_file_empty(self):
+        path = pathlib.Path("not/a/file.py")
+        with self.assertRaises(FileNotFoundError):
+            load_file(path, ".")
+
+    def test_raise_error_if_something(self):
+        dirname = os.path.dirname(__file__)
+        path = os.path.join(dirname, "../../strategies/titfortat.py")
+        bad_loader = lambda _, __: None
+        with self.assertRaises(FileNotFoundError):
+            load_file(path, ".", bad_loader)
diff --git a/axelrod/tests/unit/test_plot.py b/axelrod/tests/unit/test_plot.py
index 0db464361..e34b7fabf 100644
--- a/axelrod/tests/unit/test_plot.py
+++ b/axelrod/tests/unit/test_plot.py
@@ -255,3 +255,23 @@ def test_all_plots(self):
                 progress_bar=True,
             )
         )
+
+    def test_figure_generation_failure_violinplot(self):
+        plot = axl.Plot(self.test_result_set)
+        with self.assertRaises(RuntimeError):
+            plot._violinplot(
+                [0, 0, 0], ["a", "b", "c"], get_figure=lambda _: None
+            )
+
+    def test_figure_generation_failure_payoff_heatmap(self):
+        plot = axl.Plot(self.test_result_set)
+        with self.assertRaises(RuntimeError):
+            plot._payoff_heatmap(
+                [0, 0, 0], ["a", "b", "c"], get_figure=lambda _: None
+            )
+
+    def test_figure_generation_failure_stackplot(self):
+        plot = axl.Plot(self.test_result_set)
+        eco = axl.Ecosystem(self.test_result_set)
+        with self.assertRaises(RuntimeError):
+            plot.stackplot(eco, get_figure=lambda _: None)
diff --git a/axelrod/tournament.py b/axelrod/tournament.py
index c79775489..05dd6fead 100644
--- a/axelrod/tournament.py
+++ b/axelrod/tournament.py
@@ -28,13 +28,13 @@ def __init__(
         players: List[Player],
         name: str = "axelrod",
         game: Game = None,
-        turns: int = None,
-        prob_end: float = None,
+        turns: Optional[int] = None,
+        prob_end: Optional[float] = None,
         repetitions: int = 10,
         noise: float = 0,
-        edges: List[Tuple] = None,
-        match_attributes: dict = None,
-        seed: int = None,
+        edges: Optional[List[Tuple]] = None,
+        match_attributes: Optional[dict] = None,
+        seed: Optional[int] = None,
     ) -> None:
         """
         Parameters
@@ -110,8 +110,8 @@ def setup_output(self, filename=None):
     def play(
         self,
         build_results: bool = True,
-        filename: str = None,
-        processes: int = None,
+        filename: Optional[str] = None,
+        processes: Optional[int] = None,
         progress_bar: bool = True,
     ) -> ResultSet:
         """
diff --git a/run_mypy.py b/run_mypy.py
index 94e3d669e..c0952e7e7 100755
--- a/run_mypy.py
+++ b/run_mypy.py
@@ -49,7 +49,6 @@
     "axelrod/strategies/rand.py",
     "axelrod/strategies/titfortat.py",
     "axelrod/strategies/hmm.py",
-    "axelrod/strategies/human.py",
     "axelrod/strategies/finite_state_machines.py",
     "axelrod/strategies/worse_and_worse.py",
 ]
diff --git a/tox.ini b/tox.ini
index e40c8375b..7afca6c9d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -28,8 +28,11 @@ deps =
     isort
     black
     numpy==1.26.4
+    mypy
+    types-setuptools
 commands =
     python -m pytest --cov-report term-missing --cov=axelrod --cov-fail-under=100 . --doctest-glob="*.md" --doctest-glob="*.rst"
     python -m black -l 80 . --check
     python -m isort --check-only axelrod/.
+    python run_mypy.py
     python run_strategy_indexer.py