NOAA-GFDL · romanc · Apr 16, 2026 · Apr 16, 2026 · May 5, 2026
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
@@ -21,6 +21,15 @@ repos:
         args: ["--config-file", "pyproject.toml"]
         additional_dependencies: [types-PyYAML]
 
+  - repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v1.18.2
+    hooks:
+      - id: mypy
+        name: mypy-tests
+        args: ["--config-file", "pyproject.toml"]
+        additional_dependencies: [types-PyYAML]
+        files: tests
+
   - repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v5.0.0
     hooks:

diff --git a/tests/checkpointer/test_snapshot.py b/tests/checkpointer/test_snapshot.py
@@ -4,12 +4,12 @@
 from ndsl.checkpointer import SnapshotCheckpointer
 
 
-def test_snapshot_checkpointer_no_data():
+def test_snapshot_checkpointer_no_data() -> None:
     checkpointer = SnapshotCheckpointer(rank=0)
     xr.testing.assert_identical(checkpointer.dataset, xr.Dataset())
 
 
-def test_snapshot_checkpointer_one_snapshot():
+def test_snapshot_checkpointer_one_snapshot() -> None:
     checkpointer = SnapshotCheckpointer(rank=0)
     val1 = np.random.randn(2, 3, 4)
     checkpointer("savepoint_name", val1=val1)
@@ -27,7 +27,7 @@ def test_snapshot_checkpointer_one_snapshot():
     )
 
 
-def test_snapshot_checkpointer_multiple_snapshots():
+def test_snapshot_checkpointer_multiple_snapshots() -> None:
     checkpointer = SnapshotCheckpointer(rank=0)
     val1 = np.random.randn(2, 2, 3, 4)
     val2 = np.random.randn(1, 3, 2, 4)

diff --git a/tests/checkpointer/test_thresholds.py b/tests/checkpointer/test_thresholds.py
@@ -8,29 +8,29 @@
 )
 
 
-def test_thresholds_no_trials():
+def test_thresholds_no_trials() -> None:
     checkpointer = ThresholdCalibrationCheckpointer()
     with pytest.raises(InsufficientTrialsError):
         checkpointer.thresholds
 
 
-def test_thresholds_one_empty_trial():
+def test_thresholds_one_empty_trial() -> None:
     checkpointer = ThresholdCalibrationCheckpointer()
     with checkpointer.trial():
         pass
     with pytest.raises(InsufficientTrialsError):
         checkpointer.thresholds
 
 
-def test_thresholds_two_empty_trials():
+def test_thresholds_two_empty_trials() -> None:
     checkpointer = ThresholdCalibrationCheckpointer()
     for _ in range(2):
         with checkpointer.trial():
             pass
     assert checkpointer.thresholds.savepoints == {}
 
 
-def test_thresholds_one_data_trial():
+def test_thresholds_one_data_trial() -> None:
     checkpointer = ThresholdCalibrationCheckpointer()
     with checkpointer.trial():
         data = np.asarray([0.0, 0.0, 0.0])
@@ -50,7 +50,9 @@ def test_thresholds_one_data_trial():
         pytest.param(1.0, [-5.0, 5.0, 10.0, 0.0], 3.0, 15.0, id="more_values"),
     ],
 )
-def test_thresholds_sufficient_trials(factor, values, rel_threshold, abs_threshold):
+def test_thresholds_sufficient_trials(
+    factor: float, values: list[float], rel_threshold: float, abs_threshold: float
+) -> None:
     checkpointer = ThresholdCalibrationCheckpointer(factor=factor)
     for val in values:
         with checkpointer.trial():
@@ -63,7 +65,7 @@ def test_thresholds_sufficient_trials(factor, values, rel_threshold, abs_thresho
     }
 
 
-def test_thresholds_more_variables():
+def test_thresholds_more_variables() -> None:
     checkpointer = ThresholdCalibrationCheckpointer(factor=1.0)
     with checkpointer.trial():
         data1 = np.asarray([0.0, 0.0, 0.0])
@@ -83,7 +85,7 @@ def test_thresholds_more_variables():
     }
 
 
-def test_thresholds_two_calls():
+def test_thresholds_two_calls() -> None:
     checkpointer = ThresholdCalibrationCheckpointer(factor=1.0)
     with checkpointer.trial():
         data1 = np.asarray([0.0, 0.0, 0.0])

diff --git a/tests/checkpointer/test_validation.py b/tests/checkpointer/test_validation.py
@@ -11,7 +11,7 @@
 
 def get_dataset(
     n_savepoints: int, n_vars: int, n_ranks: int, nx: int, ny: int, nz: int
-):
+) -> xr.Dataset:
     data_vars = {}
     for i in range(n_vars):
         data_vars["data{}".format(i)] = xr.DataArray(
@@ -27,7 +27,7 @@ def get_dataset(
     return xr.Dataset(data_vars=data_vars)
 
 
-def test_validation_validates_onevar_onecall():
+def test_validation_validates_onevar_onecall() -> None:
     temp_dir = tempfile.TemporaryDirectory()
     nx_compute = 12
     nz = 20
@@ -61,7 +61,9 @@ def test_validation_validates_onevar_onecall():
         pytest.param(1.0, 0.99, id="absolute_failure"),
     ],
 )
-def test_validation_asserts_onevar_onecall(relative_threshold, absolute_threshold):
+def test_validation_asserts_onevar_onecall(
+    relative_threshold: float, absolute_threshold: float
+) -> None:
     temp_dir = tempfile.TemporaryDirectory()
     nx_compute = 12
     nz = 20
@@ -105,7 +107,9 @@ def test_validation_asserts_onevar_onecall(relative_threshold, absolute_threshol
         pytest.param(1.0, 0.99, id="absolute_threshold"),
     ],
 )
-def test_validation_passes_onevar_two_calls(relative_threshold, absolute_threshold):
+def test_validation_passes_onevar_two_calls(
+    relative_threshold: float, absolute_threshold: float
+) -> None:
     temp_dir = tempfile.TemporaryDirectory()
     nx_compute = 12
     nz = 20
@@ -155,7 +159,9 @@ def test_validation_passes_onevar_two_calls(relative_threshold, absolute_thresho
         pytest.param(1.0, 0.99, id="absolute_failure"),
     ],
 )
-def test_validation_asserts_onevar_two_calls(relative_threshold, absolute_threshold):
+def test_validation_asserts_onevar_two_calls(
+    relative_threshold: float, absolute_threshold: float
+) -> None:
     temp_dir = tempfile.TemporaryDirectory()
     nx_compute = 12
     nz = 20
@@ -207,7 +213,9 @@ def test_validation_asserts_onevar_two_calls(relative_threshold, absolute_thresh
         pytest.param(1.0, 0.99, id="absolute_failure"),
     ],
 )
-def test_validation_asserts_twovar_onecall(relative_threshold, absolute_threshold):
+def test_validation_asserts_twovar_onecall(
+    relative_threshold: float, absolute_threshold: float
+) -> None:
     temp_dir = tempfile.TemporaryDirectory()
     nx_compute = 12
     nz = 20
@@ -272,6 +280,8 @@ def test_validation_asserts_twovar_onecall(relative_threshold, absolute_threshol
         ),
     ],
 )
-def test_clip_pace_array_to_target(array, target_shape, target_array):
+def test_clip_pace_array_to_target(
+    array: np.ndarray, target_shape: tuple, target_array: np.ndarray
+) -> None:
     clipped = _clip_pace_array_to_target(array, target_shape=target_shape)
     np.testing.assert_array_equal(clipped, target_array)
diff --git a/tests/initialization/__init__.py → tests/config/__init__.py b/tests/initialization/__init__.py → tests/config/__init__.py
diff --git a/tests/config/test_backend.py b/tests/config/test_backend.py
@@ -3,7 +3,7 @@
 from ndsl import Backend
 
 
-def test_backend_building():
+def test_backend_building() -> None:
     Backend("st:python:cpu:IJK")
     Backend("st:numpy:cpu:IJK")
     Backend("st:gt:cpu:IJK")
@@ -23,7 +23,7 @@ def test_backend_building():
         Backend(unknown_backend)
 
 
-def test_backend_operators():
+def test_backend_operators() -> None:
     backend_A = Backend("st:numpy:cpu:IJK")
     backend_B = Backend("st:numpy:cpu:IJK")
 

diff --git a/tests/conftest.py b/tests/conftest.py
@@ -1,3 +1,5 @@
+from typing import Literal
+
 import numpy as np
 import pytest
 
@@ -6,15 +8,15 @@
 
 
 @pytest.fixture(params=["numpy", pytest.param("cupy", marks=pytest.mark.gpu)])
-def backend(request):
+def backend(request: pytest.FixtureRequest) -> Literal["numpy"] | Literal["cupy"]:
     if request.param == "cupy" and cupy is None:
         raise ModuleNotFoundError("cupy must be installed to run gpu tests")
 
     return request.param
 
 
 @pytest.fixture
-def ndsl_backend(backend: str):
+def ndsl_backend(backend: str) -> Backend:
     if backend == "numpy":
         return Backend("st:numpy:cpu:IJK")
 
@@ -25,7 +27,7 @@ def ndsl_backend(backend: str):
 
 
 @pytest.fixture
-def numpy(backend: str):
+def numpy(backend: str):  # type: ignore[no-untyped-def]
     if backend == "numpy":
         return np
 

diff --git a/tests/dsl/dace/stree/optimizations/test_pipeline.py b/tests/dsl/dace/stree/optimizations/test_pipeline.py
@@ -7,7 +7,7 @@
 from tests.dsl.dace.stree import StreeOptimization
 
 
-def double_map(in_field: FloatField, out_field: FloatField):
+def double_map(in_field: FloatField, out_field: FloatField) -> None:
     with computation(PARALLEL), interval(...):
         out_field = in_field
 
@@ -23,11 +23,11 @@ def __init__(self, stencil_factory: StencilFactory):
             compute_dims=[I_DIM, J_DIM, K_DIM],
         )
 
-    def __call__(self, in_field: FloatField, out_field: FloatField):
+    def __call__(self, in_field: FloatField, out_field: FloatField) -> None:
         self.stencil(in_field, out_field)
 
 
-def test_stree_roundtrip_no_opt():
+def test_stree_roundtrip_no_opt() -> None:
     domain = (3, 3, 4)
     stencil_factory, quantity_factory = get_factories_single_tile_orchestrated(
         domain[0], domain[1], domain[2], 0, backend=Backend.cpu()

diff --git a/tests/dsl/dace/stree/optimizations/test_transient_refine.py b/tests/dsl/dace/stree/optimizations/test_transient_refine.py
@@ -27,11 +27,11 @@ def stencil_with_JK_offset(in_field: FloatField, out_field: FloatField) -> None:
         out_field = in_field[J + 1, K + 1] + 3
 
 
-def stencil_with_ddim(in_field: DDIM_TYPE, out_field: DDIM_TYPE) -> None:
+def stencil_with_ddim(in_field: DDIM_TYPE, out_field: DDIM_TYPE) -> None:  # type: ignore[valid-type]
     with computation(PARALLEL), interval(...):
         n = 0
         while n < DATADIM_SIZE:
-            out_field[0, 0, 0][n] = in_field[0, 0, 0][n] + 4
+            out_field[0, 0, 0][n] = in_field[0, 0, 0][n] + 4  # type: ignore[index]
             n = n + 1
 
 

diff --git a/tests/dsl/orchestration/test_call.py b/tests/dsl/orchestration/test_call.py
@@ -11,7 +11,7 @@
 from ndsl.dsl.typing import FloatField
 
 
-def _stencil(out: Field[float]):
+def _stencil(out: Field[float]) -> None:
     with computation(PARALLEL), interval(...):
         out = out + 1
 
@@ -30,34 +30,34 @@ class AState(State):
 
 
 class OrchestratedProgram:
-    def __init__(self, stencil_factory: StencilFactory):
+    def __init__(self, stencil_factory: StencilFactory) -> None:
         orchestrate(obj=self, config=stencil_factory.config.dace_config)
         self.stencil = stencil_factory.from_dims_halo(_stencil, [I_DIM, J_DIM, K_DIM])
 
-    def __call__(self, out_qty):
+    def __call__(self, out_qty) -> None:
         self.stencil(out_qty)
 
 
 class DSLTypeProgram(NDSLRuntime):
-    def __init__(self, stencil_factory: StencilFactory):
+    def __init__(self, stencil_factory: StencilFactory) -> None:
         super().__init__(stencil_factory)
         self.stencil = stencil_factory.from_dims_halo(_stencil, [I_DIM, J_DIM, K_DIM])
 
-    def __call__(self, a_quantity: Quantity, a_state: AState):
+    def __call__(self, a_quantity: Quantity, a_state: AState) -> None:
         self.stencil(a_quantity)
         self.stencil(a_state.the_quantity)
 
 
 class GTTypeProgram(NDSLRuntime):
-    def __init__(self, stencil_factory: StencilFactory):
+    def __init__(self, stencil_factory: StencilFactory) -> None:
         super().__init__(stencil_factory)
         self.stencil = stencil_factory.from_dims_halo(_stencil, [I_DIM, J_DIM, K_DIM])
 
-    def __call__(self, a_quantity: FloatField):
+    def __call__(self, a_quantity: FloatField) -> None:
         self.stencil(a_quantity)
 
 
-def test_memory_reallocation_blind_type():
+def test_memory_reallocation_blind_type() -> None:
     stencil_factory, quantity_factory = get_factories_single_tile_orchestrated(
         5, 5, 2, 0
     )
@@ -77,7 +77,7 @@ def test_memory_reallocation_blind_type():
 
 
 @pytest.mark.xfail(reason="See https://github.com/NOAA-GFDL/NDSL/issues/436")
-def test_memory_reallocation_dsl_typehint():
+def test_memory_reallocation_dsl_typehint() -> None:
     stencil_factory, quantity_factory = get_factories_single_tile_orchestrated(
         5, 5, 2, 0
     )
@@ -95,7 +95,7 @@ def test_memory_reallocation_dsl_typehint():
     assert (state_B.the_quantity.field[0, 0, :] == 2).all()
 
 
-def test_memory_reallocation_gt4py_typehint():
+def test_memory_reallocation_gt4py_typehint() -> None:
     stencil_factory, quantity_factory = get_factories_single_tile_orchestrated(
         5, 5, 2, 0
     )
@@ -111,7 +111,7 @@ def test_memory_reallocation_gt4py_typehint():
     assert (qty_E.field[0, 0, :] == 2).all()
 
 
-def test_default_types_are_compiletime():
+def test_default_types_are_compiletime() -> None:
     stencil_factory, quantity_factory = get_factories_single_tile_orchestrated(
         5, 5, 2, 0
     )
@@ -121,7 +121,7 @@ def test_default_types_are_compiletime():
     code(qty_A, state_A)
 
 
-def test_dace_call_argument_caching():
+def test_dace_call_argument_caching() -> None:
     stencil_factory, quantity_factory = get_factories_single_tile_orchestrated(
         5, 5, 2, 0, backend=Backend.cpu()
     )

diff --git a/tests/dsl/orchestration/test_reset_mask.py b/tests/dsl/orchestration/test_reset_mask.py
@@ -5,23 +5,23 @@
 from ndsl.dsl.typing import FloatField, Int, IntFieldIJ
 
 
-def reset_mask(dp1: FloatField, pe1: FloatField, mask: IntFieldIJ):
+def reset_mask(dp1: FloatField, pe1: FloatField, mask: IntFieldIJ) -> None:
     with computation(PARALLEL), interval(...):
         dp1 = pe1[0, 0, 1] - pe1
     with computation(FORWARD), interval(0, 1):
         mask = 0
 
 
-def conditional_copy(dp1: FloatField, pe1: FloatField, mask: IntFieldIJ):
+def conditional_copy(dp1: FloatField, pe1: FloatField, mask: IntFieldIJ) -> None:
     with computation(PARALLEL), interval(0, 1):
         if mask == 1:
             dp1 = pe1
 
 
-class OrchestratedProgramm(NDSLRuntime):
+class OrchestratedProgram(NDSLRuntime):
     def __init__(
         self, stencil_factory: StencilFactory, quantity_factory: QuantityFactory
-    ):
+    ) -> None:
         super().__init__(stencil_factory)
 
         self._reset_mask = self._stencil_factory.from_dims_halo(
@@ -42,14 +42,14 @@ def mask_has_been_reset(self) -> bool:
         return (self._mask.field[:] == 0).all()
 
 
-def test_conditional_copy_with_mask():
+def test_conditional_copy_with_mask() -> None:
     stencil_factory, quantity_factory = get_factories_single_tile_orchestrated(
         nx=4, ny=5, nz=6, nhalo=1
     )
 
     dp1 = quantity_factory.zeros(dims=[I_DIM, J_DIM, K_DIM], units="")
     pe1 = quantity_factory.zeros(dims=[I_DIM, J_DIM, K_DIM], units="")
-    code = OrchestratedProgramm(stencil_factory, quantity_factory)
+    code = OrchestratedProgram(stencil_factory, quantity_factory)
 
     code(dp1, pe1)