diff --git a/pyproject.toml b/pyproject.toml
index 4b866d5ebb..f4e458fa4b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -264,6 +264,14 @@ concurrency = ["multiprocessing"]
 ignore_missing_imports = true
 allow_redefinition = true
 disable_error_code = ["call-overload", "operator"]
+strict = false
+enable_error_code = ["ignore-without-code", "redundant-expr", "truthy-bool"]
+exclude = [
+    "^build/",
+    "^build/lib/",
+    "^docs/conf\\.py$",
+    "^examples/scripts/"
+]
 
 [[tool.mypy.overrides]]
 module = [
diff --git a/src/pybamm/experiment/experiment.py b/src/pybamm/experiment/experiment.py
index ce44457cb2..b9cd4b4d9d 100644
--- a/src/pybamm/experiment/experiment.py
+++ b/src/pybamm/experiment/experiment.py
@@ -40,7 +40,9 @@ class Experiment:
 
     def __init__(
         self,
-        operating_conditions: list[str | tuple[str] | BaseStep],
+        operating_conditions: list[
+            str | tuple[str, ...] | tuple[str | BaseStep] | BaseStep
+        ],
         period: str | None = None,
         temperature: float | None = None,
         termination: list[str] | None = None,
diff --git a/src/pybamm/experiment/step/base_step.py b/src/pybamm/experiment/step/base_step.py
index ebbc4057c4..98c612781a 100644
--- a/src/pybamm/experiment/step/base_step.py
+++ b/src/pybamm/experiment/step/base_step.py
@@ -140,7 +140,7 @@ def __init__(
             self.value = pybamm.Interpolant(
                 t,
                 y,
-                pybamm.t - pybamm.InputParameter("start time"),
+                [pybamm.t - pybamm.InputParameter("start time")],
                 name="Drive Cycle",
             )
             self.period = np.diff(t).min()
diff --git a/src/pybamm/expression_tree/binary_operators.py b/src/pybamm/expression_tree/binary_operators.py
index efd9874664..c0dd6017bd 100644
--- a/src/pybamm/expression_tree/binary_operators.py
+++ b/src/pybamm/expression_tree/binary_operators.py
@@ -2,7 +2,6 @@
 # Binary operator classes
 #
 from __future__ import annotations
-import numbers
 
 import numpy as np
 import numpy.typing as npt
@@ -34,8 +33,8 @@ def _preprocess_binary(
             raise ValueError("right must be a 1D array")
         right = pybamm.Vector(right)
 
-    # Check both left and right are pybamm Symbols
-    if not (isinstance(left, pybamm.Symbol) and isinstance(right, pybamm.Symbol)):
+    # Check right is pybamm Symbol
+    if not isinstance(right, pybamm.Symbol):
         raise NotImplementedError(
             f"BinaryOperator not implemented for symbols of type {type(left)} and {type(right)}"
         )
@@ -114,6 +113,9 @@ def __str__(self):
             right_str = f"{self.right!s}"
         return f"{left_str} {self.name} {right_str}"
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return self.__class__(self.name, left, right)  # pragma: no cover
+
     def create_copy(
         self,
         new_children: list[pybamm.Symbol] | None = None,
@@ -128,7 +130,7 @@ def create_copy(
         children = self._children_for_copying(new_children)
 
         if not perform_simplifications:
-            out = self.__class__(children[0], children[1])
+            out = self._new_instance(children[0], children[1])
         else:
             # creates a new instance using the overloaded binary operator to perform
             # additional simplifications, rather than just calling the constructor
@@ -225,6 +227,9 @@ def __init__(
         """See :meth:`pybamm.BinaryOperator.__init__()`."""
         super().__init__("**", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return Power(left, right)
+
     def _diff(self, variable: pybamm.Symbol):
         """See :meth:`pybamm.Symbol._diff()`."""
         # apply chain rule and power rule
@@ -274,6 +279,9 @@ def __init__(
         """See :meth:`pybamm.BinaryOperator.__init__()`."""
         super().__init__("+", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return Addition(left, right)
+
     def _diff(self, variable: pybamm.Symbol):
         """See :meth:`pybamm.Symbol._diff()`."""
         return self.left.diff(variable) + self.right.diff(variable)
@@ -301,6 +309,9 @@ def __init__(
 
         super().__init__("-", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return Subtraction(left, right)
+
     def _diff(self, variable: pybamm.Symbol):
         """See :meth:`pybamm.Symbol._diff()`."""
         return self.left.diff(variable) - self.right.diff(variable)
@@ -330,6 +341,9 @@ def __init__(
 
         super().__init__("*", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return Multiplication(left, right)
+
     def _diff(self, variable: pybamm.Symbol):
         """See :meth:`pybamm.Symbol._diff()`."""
         # apply product rule
@@ -370,6 +384,9 @@ def __init__(
         """See :meth:`pybamm.BinaryOperator.__init__()`."""
         super().__init__("@", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return MatrixMultiplication(left, right)  # pragma: no cover
+
     def diff(self, variable):
         """See :meth:`pybamm.Symbol.diff()`."""
         # We shouldn't need this
@@ -419,6 +436,9 @@ def __init__(
         """See :meth:`pybamm.BinaryOperator.__init__()`."""
         super().__init__("/", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return Division(left, right)
+
     def _diff(self, variable: pybamm.Symbol):
         """See :meth:`pybamm.Symbol._diff()`."""
         # apply quotient rule
@@ -467,6 +487,9 @@ def __init__(
         """See :meth:`pybamm.BinaryOperator.__init__()`."""
         super().__init__("inner product", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return Inner(left, right)  # pragma: no cover
+
     def _diff(self, variable: pybamm.Symbol):
         """See :meth:`pybamm.Symbol._diff()`."""
         # apply product rule
@@ -544,6 +567,9 @@ def __init__(
         """See :meth:`pybamm.BinaryOperator.__init__()`."""
         super().__init__("==", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return Equality(left, right)
+
     def diff(self, variable):
         """See :meth:`pybamm.Symbol.diff()`."""
         # Equality should always be multiplied by something else so hopefully don't
@@ -601,6 +627,10 @@ def __init__(
     ):
         """See :meth:`pybamm.BinaryOperator.__init__()`."""
         super().__init__(name, left, right)
+        self.name = name
+
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return _Heaviside(self.name, left, right)  # pragma: no cover
 
     def diff(self, variable):
         """See :meth:`pybamm.Symbol.diff()`."""
@@ -679,6 +709,9 @@ def __init__(
     ):
         super().__init__("%", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return Modulo(left, right)
+
     def _diff(self, variable: pybamm.Symbol):
         """See :meth:`pybamm.Symbol._diff()`."""
         # apply chain rule and power rule
@@ -721,6 +754,9 @@ def __init__(
     ):
         super().__init__("minimum", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return Minimum(left, right)
+
     def __str__(self):
         """See :meth:`pybamm.Symbol.__str__()`."""
         return f"minimum({self.left!s}, {self.right!s})"
@@ -765,6 +801,9 @@ def __init__(
     ):
         super().__init__("maximum", left, right)
 
+    def _new_instance(self, left: pybamm.Symbol, right: pybamm.Symbol) -> pybamm.Symbol:
+        return Maximum(left, right)
+
     def __str__(self):
         """See :meth:`pybamm.Symbol.__str__()`."""
         return f"maximum({self.left!s}, {self.right!s})"
@@ -1539,7 +1578,7 @@ def source(
         corresponding to a source term in the bulk.
     """
     # Broadcast if left is number
-    if isinstance(left, numbers.Number):
+    if isinstance(left, (int, float)):
         left = pybamm.PrimaryBroadcast(left, "current collector")
 
     # force type cast for mypy
diff --git a/src/pybamm/expression_tree/broadcasts.py b/src/pybamm/expression_tree/broadcasts.py
index 6045c3f3e8..1fabef127c 100644
--- a/src/pybamm/expression_tree/broadcasts.py
+++ b/src/pybamm/expression_tree/broadcasts.py
@@ -78,8 +78,7 @@ def _from_json(cls, snippet):
         )
 
     def _unary_new_copy(self, child: pybamm.Symbol, perform_simplifications=True):
-        """See :meth:`pybamm.UnaryOperator._unary_new_copy()`."""
-        return self.__class__(child, self.broadcast_domain)
+        pass  # pragma: no cover
 
 
 class PrimaryBroadcast(Broadcast):
@@ -191,6 +190,10 @@ def reduce_one_dimension(self):
         """Reduce the broadcast by one dimension."""
         return self.orphans[0]
 
+    def _unary_new_copy(self, child: pybamm.Symbol, perform_simplifications=True):
+        """See :meth:`pybamm.UnaryOperator._unary_new_copy()`."""
+        return self.__class__(child, self.broadcast_domain)
+
 
 class PrimaryBroadcastToEdges(PrimaryBroadcast):
     """A primary broadcast onto the edges of the domain."""
@@ -321,6 +324,10 @@ def reduce_one_dimension(self):
         """Reduce the broadcast by one dimension."""
         return self.orphans[0]
 
+    def _unary_new_copy(self, child: pybamm.Symbol, perform_simplifications=True):
+        """See :meth:`pybamm.UnaryOperator._unary_new_copy()`."""
+        return self.__class__(child, self.broadcast_domain)
+
 
 class SecondaryBroadcastToEdges(SecondaryBroadcast):
     """A secondary broadcast onto the edges of a domain."""
@@ -438,6 +445,10 @@ def reduce_one_dimension(self):
         """Reduce the broadcast by one dimension."""
         raise NotImplementedError
 
+    def _unary_new_copy(self, child: pybamm.Symbol, perform_simplifications=True):
+        """See :meth:`pybamm.UnaryOperator._unary_new_copy()`."""
+        return self.__class__(child, self.broadcast_domain)
+
 
 class TertiaryBroadcastToEdges(TertiaryBroadcast):
     """A tertiary broadcast onto the edges of a domain."""
@@ -463,7 +474,7 @@ def __init__(
         self,
         child_input: Numeric | pybamm.Symbol,
         broadcast_domain: DomainType = None,
-        auxiliary_domains: AuxiliaryDomainType = None,
+        auxiliary_domains: AuxiliaryDomainType | str = None,
         broadcast_domains: DomainsType = None,
         name: str | None = None,
     ):
diff --git a/src/pybamm/expression_tree/concatenations.py b/src/pybamm/expression_tree/concatenations.py
index 6f190aaf59..50abf5c29f 100644
--- a/src/pybamm/expression_tree/concatenations.py
+++ b/src/pybamm/expression_tree/concatenations.py
@@ -516,7 +516,7 @@ def substrings(s: str):
             yield s[i : j + 1]
 
 
-def intersect(s1: str, s2: str):
+def intersect(s1: str, s2: str) -> str:
     # find all the common strings between two strings
     all_intersects = set(substrings(s1)) & set(substrings(s2))
     # intersect is the longest such intercept
@@ -527,7 +527,7 @@ def intersect(s1: str, s2: str):
     return intersect.lstrip().rstrip()
 
 
-def simplified_concatenation(*children, name: str | None = None):
+def simplified_concatenation(*children: pybamm.Symbol, name: str | None = None):
     """Perform simplifications on a concatenation."""
     # remove children that are None
     children = list(filter(lambda x: x is not None, children))
@@ -543,7 +543,8 @@ def simplified_concatenation(*children, name: str | None = None):
         # Create Concatenation to easily read domains
         concat = Concatenation(*children, name=name)
         if all(
-            isinstance(child, pybamm.Broadcast) and child.child == children[0].child
+            isinstance(child, pybamm.Broadcast)
+            and getattr(child, "child", None) == getattr(children[0], "child", None)
             for child in children
         ):
             unique_child = children[0].orphans[0]
diff --git a/src/pybamm/expression_tree/symbol.py b/src/pybamm/expression_tree/symbol.py
index 34ca9d627b..96dc3a844f 100644
--- a/src/pybamm/expression_tree/symbol.py
+++ b/src/pybamm/expression_tree/symbol.py
@@ -965,7 +965,9 @@ def to_casadi(
         """
         return pybamm.CasadiConverter(casadi_symbols).convert(self, t, y, y_dot, inputs)
 
-    def _children_for_copying(self, children: list[Symbol] | None = None) -> Symbol:
+    def _children_for_copying(
+        self, children: list[Symbol] | None = None
+    ) -> list[Symbol]:
         """
         Gets existing children for a symbol being copied if they aren't provided.
         """
diff --git a/src/pybamm/models/base_model.py b/src/pybamm/models/base_model.py
index a8dc6aa5ea..59b97a8e87 100644
--- a/src/pybamm/models/base_model.py
+++ b/src/pybamm/models/base_model.py
@@ -77,6 +77,8 @@ def __init__(self, name="Unnamed model"):
         self.use_jacobian = True
         self.convert_to_format = "casadi"
 
+        self.calculate_sensitivities: list[str] = []
+
         # Model is not initially discretised
         self.is_discretised = False
         self.y_slices = None
diff --git a/src/pybamm/plotting/quick_plot.py b/src/pybamm/plotting/quick_plot.py
index ee146a2002..6a4fce9a04 100644
--- a/src/pybamm/plotting/quick_plot.py
+++ b/src/pybamm/plotting/quick_plot.py
@@ -126,7 +126,7 @@ def __init__(
         # Set colors, linestyles, figsize, axis limits
         # call LoopList to make sure list index never runs out
         if colors is None:
-            self.colors = LoopList(colors or ["r", "b", "k", "g", "m", "c"])
+            self.colors = LoopList(["r", "b", "k", "g", "m", "c"])
         else:
             self.colors = LoopList(colors)
         self.linestyles = LoopList(linestyles or ["-", ":", "--", "-."])
diff --git a/src/pybamm/solvers/base_solver.py b/src/pybamm/solvers/base_solver.py
index 49e9b928ae..4cd219fd3e 100644
--- a/src/pybamm/solvers/base_solver.py
+++ b/src/pybamm/solvers/base_solver.py
@@ -94,8 +94,8 @@ def supports_parallel_solve(self):
     def requires_explicit_sensitivities(self):
         return True
 
-    @root_method.setter
-    def root_method(self, method):
+    @root_method.setter  # type: ignore[attr-defined, no-redef]
+    def root_method(self, method) -> None:
         if method == "casadi":
             method = pybamm.CasadiAlgebraicSolver(self.root_tol)
         elif isinstance(method, str):
@@ -1122,7 +1122,7 @@ def _set_sens_initial_conditions_from(
         """
 
         ninputs = len(model.calculate_sensitivities)
-        initial_conditions = tuple([] for _ in range(ninputs))
+        initial_conditions: tuple[list[float], ...] = tuple([] for _ in range(ninputs))
         solution = solution.last_state
         for var in model.initial_conditions:
             final_state = solution[var.name]
@@ -1143,10 +1143,10 @@ def _set_sens_initial_conditions_from(
         slices = [y_slices[symbol][0] for symbol in model.initial_conditions.keys()]
 
         # sort equations according to slices
-        concatenated_initial_conditions = [
+        concatenated_initial_conditions = tuple(
             casadi.vertcat(*[eq for _, eq in sorted(zip(slices, init))])
             for init in initial_conditions
-        ]
+        )
         return concatenated_initial_conditions
 
     def process_t_interp(self, t_interp):
diff --git a/src/pybamm/solvers/idaklu_jax.py b/src/pybamm/solvers/idaklu_jax.py
index ef505570fa..6cfa624490 100644
--- a/src/pybamm/solvers/idaklu_jax.py
+++ b/src/pybamm/solvers/idaklu_jax.py
@@ -259,9 +259,9 @@ def f_isolated(*args, **kwargs):
 
     def jax_value(
         self,
-        t: npt.NDArray = None,
-        inputs: Union[dict, None] = None,
-        output_variables: Union[list[str], None] = None,
+        t: npt.NDArray | None = None,
+        inputs: dict | None = None,
+        output_variables: list[str] | None = None,
     ):
         """Helper function to compute the gradient of a jaxified expression
 
@@ -292,9 +292,9 @@ def jax_value(
 
     def jax_grad(
         self,
-        t: npt.NDArray = None,
-        inputs: Union[dict, None] = None,
-        output_variables: Union[list[str], None] = None,
+        t: npt.NDArray | None = None,
+        inputs: dict | None = None,
+        output_variables: list[str] | None = None,
     ):
         """Helper function to compute the gradient of a jaxified expression
 
diff --git a/src/pybamm/solvers/processed_variable_time_integral.py b/src/pybamm/solvers/processed_variable_time_integral.py
index ce41c1796e..8b2f5712c8 100644
--- a/src/pybamm/solvers/processed_variable_time_integral.py
+++ b/src/pybamm/solvers/processed_variable_time_integral.py
@@ -7,7 +7,7 @@
 @dataclass
 class ProcessedVariableTimeIntegral:
     method: Literal["discrete", "continuous"]
-    initial_condition: npt.NDArray
+    initial_condition: npt.NDArray | float
     discrete_times: Optional[npt.NDArray]
 
     @staticmethod
diff --git a/src/pybamm/solvers/solution.py b/src/pybamm/solvers/solution.py
index 4f17c60d94..d96a667344 100644
--- a/src/pybamm/solvers/solution.py
+++ b/src/pybamm/solvers/solution.py
@@ -160,7 +160,7 @@ def __init__(
     def has_sensitivities(self) -> bool:
         if isinstance(self._all_sensitivities, bool):
             return self._all_sensitivities
-        elif isinstance(self._all_sensitivities, dict):
+        else:
             return len(self._all_sensitivities) > 0
 
     def extract_explicit_sensitivities(self):
diff --git a/src/pybamm/solvers/summary_variable.py b/src/pybamm/solvers/summary_variable.py
index 4c3da92a42..26dd40e174 100644
--- a/src/pybamm/solvers/summary_variable.py
+++ b/src/pybamm/solvers/summary_variable.py
@@ -4,7 +4,8 @@
 from __future__ import annotations
 import pybamm
 import numpy as np
-from typing import Any
+from typing import Any, cast
+from numpy.typing import NDArray
 
 
 class SummaryVariables:
@@ -40,12 +41,15 @@ def __init__(
     ):
         self.user_inputs = user_inputs or {}
         self.esoh_solver = esoh_solver
-        self._variables = {}  # Store computed variables
+
+        self._variables: dict[str, float | list[float]] = {}  # Store computed variables
         self.cycle_number = np.array([])
+        self.cycles: list[SummaryVariables] | None = None
+        self._all_variables: list[str] | None = None
 
         model = solution.all_models[0]
         self._possible_variables = model.summary_variables  # minus esoh variables
-        self._esoh_variables = None  # Store eSOH variable names
+        self._esoh_variables: list[str] | None = None  # Store eSOH variable names
 
         # Flag if eSOH calculations are needed
         self.calc_esoh = (
@@ -81,31 +85,34 @@ def all_variables(self) -> list[str]:
         Return names of all possible summary variables, including eSOH variables
          if appropriate.
         """
-        try:
-            return self._all_variables
-        except AttributeError:
-            base_vars = self._possible_variables.copy()
-            base_vars.extend(
-                f"Change in {var[0].lower() + var[1:]}"
-                for var in self._possible_variables
-            )
+        all_vars = getattr(self, "_all_variables", None)
+        if all_vars is not None:
+            return all_vars
+        base_vars = self._possible_variables.copy()
+        base_vars.extend(
+            f"Change in {var[0].lower() + var[1:]}" for var in self._possible_variables
+        )
 
-            if self.calc_esoh:
-                base_vars.extend(self.esoh_variables)
+        if self.calc_esoh:
+            base_vars.extend(self.esoh_variables)
 
-            self._all_variables = base_vars
-            return self._all_variables
+        self._all_variables = base_vars
+        return base_vars
 
     @property
     def esoh_variables(self) -> list[str] | None:
         """Return names of all eSOH variables."""
-        if self.calc_esoh and self._esoh_variables is None:
+        if (
+            self.esoh_solver is not None
+            and self.calc_esoh
+            and self._esoh_variables is None
+        ):
             esoh_model = self.esoh_solver._get_electrode_soh_sims_full().model
             esoh_vars = list(esoh_model.variables.keys())
             self._esoh_variables = esoh_vars
         return self._esoh_variables
 
-    def __getitem__(self, key: str) -> float | list[float]:
+    def __getitem__(self, key: str) -> float | list[float] | NDArray[Any]:
         """
         Access or compute a summary variable by its name.
 
@@ -148,10 +155,11 @@ def update(self, var: str):
 
     def _update_multiple_cycles(self, var: str, var_lowercase: str):
         """Creates aggregated summary variables for where more than one cycle exists."""
-        var_cycle = [cycle[var] for cycle in self.cycles]
-        change_var_cycle = [
-            cycle[f"Change in {var_lowercase}"] for cycle in self.cycles
-        ]
+        cycles = cast(list[SummaryVariables], self.cycles)
+        var_cycle = cast(list[float], [cycle[var] for cycle in cycles])
+        change_var_cycle = cast(
+            list[float], [cycle[f"Change in {var_lowercase}"] for cycle in cycles]
+        )
         self._variables[var] = var_cycle
         self._variables[f"Change in {var_lowercase}"] = change_var_cycle
 
@@ -180,8 +188,9 @@ def _get_esoh_variables(self) -> dict[str, float]:
         Q_p = self.last_state["Positive electrode capacity [A.h]"].data[0]
         Q_Li = self.last_state["Total lithium capacity in particles [A.h]"].data[0]
         all_inputs = {**self.user_inputs, "Q_n": Q_n, "Q_p": Q_p, "Q_Li": Q_Li}
+        esoh_solver = cast(pybamm.lithium_ion.ElectrodeSOHSolver, self.esoh_solver)
         try:
-            esoh_sol = self.esoh_solver.solve(inputs=all_inputs)
+            esoh_sol = esoh_solver.solve(inputs=all_inputs)
         except pybamm.SolverError as error:  # pragma: no cover
             raise pybamm.SolverError(
                 "Could not solve for eSOH summary variables"
diff --git a/src/pybamm/telemetry.py b/src/pybamm/telemetry.py
index 3825738d47..ac5103139b 100644
--- a/src/pybamm/telemetry.py
+++ b/src/pybamm/telemetry.py
@@ -1,3 +1,4 @@
+from typing import cast
 from posthog import Posthog
 import pybamm
 import sys
@@ -20,7 +21,7 @@ def capture(**kwargs):  # pragma: no cover
         project_api_key="phc_acTt7KxmvBsAxaE0NyRd5WfJyNxGvBq1U9HnlQSztmb",
         host="https://us.i.posthog.com",
     )
-    _posthog.log.setLevel("CRITICAL")
+    cast(Posthog, _posthog).log.setLevel("CRITICAL")
 
 
 def disable():
diff --git a/src/pybamm/util.py b/src/pybamm/util.py
index aac8e7127d..7abaf39888 100644
--- a/src/pybamm/util.py
+++ b/src/pybamm/util.py
@@ -152,7 +152,7 @@ def search(
             Default is 0.4
         """
 
-        if not isinstance(keys, (str, list)) or not all(
+        if not isinstance(keys, (str, list)) or not all(  # type: ignore[redundant-expr]
             isinstance(k, str) for k in keys
         ):
             msg = f"'keys' must be a string or a list of strings, got {type(keys)}"
diff --git a/tests/unit/test_expression_tree/test_binary_operators.py b/tests/unit/test_expression_tree/test_binary_operators.py
index eba3ca1bbd..ceed90fda2 100644
--- a/tests/unit/test_expression_tree/test_binary_operators.py
+++ b/tests/unit/test_expression_tree/test_binary_operators.py
@@ -11,7 +11,7 @@
 import pybamm
 import sympy
 
-EMPTY_DOMAINS = {
+EMPTY_DOMAINS: dict[str, list[str]] = {
     "primary": [],
     "secondary": [],
     "tertiary": [],
diff --git a/tests/unit/test_expression_tree/test_operations/test_copy.py b/tests/unit/test_expression_tree/test_operations/test_copy.py
index f0d59a1fe1..67a884771c 100644
--- a/tests/unit/test_expression_tree/test_operations/test_copy.py
+++ b/tests/unit/test_expression_tree/test_operations/test_copy.py
@@ -79,6 +79,7 @@ def test_symbol_create_copy_new_children(self):
                 a * b,
                 a / b,
                 a**b,
+                b % a,
                 pybamm.minimum(a, b),
                 pybamm.maximum(a, b),
                 pybamm.Equality(a, b),
@@ -89,12 +90,15 @@ def test_symbol_create_copy_new_children(self):
                 b * a,
                 b / a,
                 b**a,
+                b % a,
                 pybamm.minimum(b, a),
                 pybamm.maximum(b, a),
                 pybamm.Equality(b, a),
             ],
         ):
-            new_symbol = symbol_ab.create_copy(new_children=[b, a])
+            new_symbol = symbol_ab.create_copy(
+                new_children=[b, a], perform_simplifications=False
+            )
             assert new_symbol == symbol_ba
             assert new_symbol.print_name == symbol_ba.print_name
 
diff --git a/tests/unit/test_solvers/test_solution.py b/tests/unit/test_solvers/test_solution.py
index 78a8dca58e..325d1f3adc 100644
--- a/tests/unit/test_solvers/test_solution.py
+++ b/tests/unit/test_solvers/test_solution.py
@@ -253,7 +253,7 @@ def test_copy_with_computed_variables(self):
 
         sol2 = sol1.copy()
 
-        assert (
+        assert all(
             sol1._variables[k] == sol2._variables[k] for k in sol1._variables.keys()
         )
         assert sol2.variables_returned is True