diff --git a/src/ria_toolkit_oss/datatypes/datasets/dataset_builder.py b/src/ria_toolkit_oss/datatypes/datasets/dataset_builder.py
index 241bbdf..fa34130 100644
--- a/src/ria_toolkit_oss/datatypes/datasets/dataset_builder.py
+++ b/src/ria_toolkit_oss/datatypes/datasets/dataset_builder.py
@@ -21,7 +21,8 @@ class DatasetBuilder(ABC):
     """
 
     _url: str = abstract_attribute()
-    _SHA256: str  # SHA256 checksum.
+    _SHA256: Optional[str] = None  # SHA256 checksum.
+    _MD5: Optional[str] = None  # MD5 checksum.
     _name: str = abstract_attribute()
     _author: str = abstract_attribute()
     _license: DatasetLicense = abstract_attribute()
diff --git a/src/ria_toolkit_oss/datatypes/datasets/h5helpers.py b/src/ria_toolkit_oss/datatypes/datasets/h5helpers.py
index b06a570..d35a771 100644
--- a/src/ria_toolkit_oss/datatypes/datasets/h5helpers.py
+++ b/src/ria_toolkit_oss/datatypes/datasets/h5helpers.py
@@ -169,8 +169,10 @@ def delete_example_inplace(source: str | os.PathLike, idx: int) -> None:
     with h5py.File(source, "a") as f:
         ds, md = f["data"], f["metadata/metadata"]
         m, c, n = ds.shape
-        assert 0 <= idx <= m - 1
-        assert len(ds) == len(md)
+        if not (0 <= idx <= m - 1):
+            raise IndexError(f"Index {idx} out of range [0, {m - 1}]")
+        if len(ds) != len(md):
+            raise ValueError("Data and metadata array lengths do not match")
 
         new_ds = f.create_dataset(
             "data.temp",
diff --git a/src/ria_toolkit_oss/datatypes/datasets/radio_dataset.py b/src/ria_toolkit_oss/datatypes/datasets/radio_dataset.py
index 7a70589..1ee9646 100644
--- a/src/ria_toolkit_oss/datatypes/datasets/radio_dataset.py
+++ b/src/ria_toolkit_oss/datatypes/datasets/radio_dataset.py
@@ -255,7 +255,9 @@ class RadioDataset(ABC):
             else:
                 classes_to_augment = classes_to_augment.encode("utf-8")
                 if classes_to_augment not in class_sizes:
-                    raise ValueError(f"class name of {i} does not belong to the class key of {class_key}")
+                    raise ValueError(
+                        f"class name of {classes_to_augment} does not belong to the class key of {class_key}"
+                    )
 
         result_sizes = get_result_sizes(
             level=level, target_size=target_size, classes_to_augment=classes_to_augment, class_sizes=class_sizes
@@ -375,7 +377,7 @@ class RadioDataset(ABC):
             counters[key] = counters.get(key, 0)
 
         idx = 0
-        with h5py.File(self.source, "a") as f:
+        with h5py.File(self.source, "r") as f:
             while idx < len(self):
                 labels = f["metadata/metadata"][class_key]
                 current_class = labels[idx]
@@ -514,7 +516,7 @@ class RadioDataset(ABC):
 
         idx = 0
 
-        with h5py.File(self.source, "a") as f:
+        with h5py.File(self.source, "r") as f:
             while idx < len(self):
                 labels = f["metadata/metadata"][class_key]
                 current_class = labels[idx]
diff --git a/src/ria_toolkit_oss/datatypes/datasets/split.py b/src/ria_toolkit_oss/datatypes/datasets/split.py
index d70b9a9..4ef7faf 100644
--- a/src/ria_toolkit_oss/datatypes/datasets/split.py
+++ b/src/ria_toolkit_oss/datatypes/datasets/split.py
@@ -247,7 +247,7 @@ def _validate_sublists(list_of_lists: list[list[str]], ids: list[str]) -> None:
     """Ensure that each ID is present in one and only one sublist."""
     all_elements = [item for sublist in list_of_lists for item in sublist]
 
-    assert len(all_elements) == len(set(all_elements)) and list(set(ids)).sort() == list(set(all_elements)).sort()
+    assert len(all_elements) == len(set(all_elements)) and sorted(set(ids)) == sorted(set(all_elements))
 
 
 def _generate_split_source_filenames(
diff --git a/src/ria_toolkit_oss/datatypes/recording.py b/src/ria_toolkit_oss/datatypes/recording.py
index 417dee8..11989f9 100644
--- a/src/ria_toolkit_oss/datatypes/recording.py
+++ b/src/ria_toolkit_oss/datatypes/recording.py
@@ -146,7 +146,7 @@ class Recording:
                 self._metadata["timestamp"] = time.time()
         else:
             if not isinstance(self._metadata["timestamp"], (int, float)):
-                raise ValueError("timestamp must be int or float, not ", type(self._metadata["timestamp"]))
+                raise ValueError(f"timestamp must be int or float, not {type(self._metadata['timestamp'])}")
 
         if "rec_id" not in self.metadata:
             self._metadata["rec_id"] = generate_recording_id(data=self.data, timestamp=self._metadata["timestamp"])
@@ -445,7 +445,7 @@ class Recording:
         'rec_id': 'fda0f41...'}  # Example value
         """
         if key not in PROTECTED_KEYS:
-            self._metadata.pop(key)
+            self._metadata.pop(key, None)
         else:
             raise ValueError(f"Key {key} is protected and cannot be modified or removed.")
 
diff --git a/src/ria_toolkit_oss/io/recording.py b/src/ria_toolkit_oss/io/recording.py
index 27aeee1..ae38bc8 100644
--- a/src/ria_toolkit_oss/io/recording.py
+++ b/src/ria_toolkit_oss/io/recording.py
@@ -330,7 +330,7 @@ def to_sigmf(
     converted_metadata = {
         sigmf_key: metadata[metadata_key]
         for sigmf_key, metadata_key in SIGMF_KEY_CONVERSION.items()
-        if metadata_key in metadata
+        if metadata_key in metadata and sigmf_key != SigMFFile.HASH_KEY
     }
 
     # Merge dictionaries, giving priority to sigmf_meta
@@ -387,9 +387,8 @@ def from_sigmf(file: os.PathLike | str) -> Recording:
     """
 
     file = str(file)
-    if len(file) > 11:
-        if file[-11:-5] != ".sigmf":
-            file = file + ".sigmf-data"
+    if not file.endswith((".sigmf-data", ".sigmf-meta", ".sigmf")):
+        file = file + ".sigmf-data"
 
     sigmf_file = sigmffile.fromfile(file)
 
diff --git a/src/ria_toolkit_oss/orchestration/campaign.py b/src/ria_toolkit_oss/orchestration/campaign.py
index 61c3cb6..9d96c96 100644
--- a/src/ria_toolkit_oss/orchestration/campaign.py
+++ b/src/ria_toolkit_oss/orchestration/campaign.py
@@ -213,7 +213,7 @@ class CaptureStep:
             bandwidth_mhz=parse_bandwidth_mhz(d.get("bandwidth")),
             traffic=d.get("traffic"),
             connection_interval_ms=d.get("connection_interval_ms"),
-            power_dbm=float(d["power"].rstrip("dBm").strip()) if d.get("power") else None,
+            power_dbm=float(d["power"].removesuffix("dBm").strip()) if d.get("power") else None,
         )
 
 
diff --git a/src/ria_toolkit_oss/orchestration/executor.py b/src/ria_toolkit_oss/orchestration/executor.py
index 1805915..629c0d8 100644
--- a/src/ria_toolkit_oss/orchestration/executor.py
+++ b/src/ria_toolkit_oss/orchestration/executor.py
@@ -139,9 +139,9 @@ def _run_script(script: str, *args: str, timeout: float = 15.0) -> str:
     Returns:
         Script stdout as a string.
     """
-    script_path = Path(script).resolve()
-    if not script_path.is_absolute():
+    if not Path(script).is_absolute():
         raise RuntimeError(f"Script path must be absolute: {script}")
+    script_path = Path(script).resolve()
     if not script_path.is_file():
         raise RuntimeError(f"Script not found or is not a regular file: {script}")
 
diff --git a/src/ria_toolkit_oss/orchestration/qa.py b/src/ria_toolkit_oss/orchestration/qa.py
index efa1395..8836e75 100644
--- a/src/ria_toolkit_oss/orchestration/qa.py
+++ b/src/ria_toolkit_oss/orchestration/qa.py
@@ -51,7 +51,7 @@ def estimate_snr_db(samples: np.ndarray, signal_fraction: float = 0.7) -> float:
     psd = np.abs(np.fft.fft(samples[:n_fft] * window)) ** 2
 
     psd_sorted = np.sort(psd)[::-1]
-    n_signal = max(1, int(n_fft * signal_fraction))
+    n_signal = min(max(1, int(n_fft * signal_fraction)), n_fft - 1)
     signal_power = psd_sorted[:n_signal].mean()
     noise_power = psd_sorted[n_signal:].mean()
 
diff --git a/src/ria_toolkit_oss/sdr/pluto.py b/src/ria_toolkit_oss/sdr/pluto.py
index 47af8df..52cd7e6 100644
--- a/src/ria_toolkit_oss/sdr/pluto.py
+++ b/src/ria_toolkit_oss/sdr/pluto.py
@@ -333,7 +333,12 @@ class Pluto(SDR):
         elif tx_time is not None:
             pass
         else:
-            tx_time = len(recording) / self.tx_sample_rate
+            if isinstance(recording, Recording):
+                tx_time = recording.data.shape[-1] / self.tx_sample_rate
+            elif isinstance(recording, np.ndarray):
+                tx_time = recording.shape[-1] / self.tx_sample_rate
+            else:
+                tx_time = len(recording[0]) / self.tx_sample_rate
 
         data = self._format_tx_data(recording=recording)
 
@@ -437,7 +442,7 @@ class Pluto(SDR):
                 abs_gain = gain
 
             if abs_gain < rx_gain_min or abs_gain > rx_gain_max:
-                abs_gain = min(max(gain, rx_gain_min), rx_gain_max)
+                abs_gain = min(max(abs_gain, rx_gain_min), rx_gain_max)
                 print(f"Gain {gain} out of range for Pluto.")
                 print(f"Gain range: {rx_gain_min} to {rx_gain_max} dB")
 
@@ -591,6 +596,8 @@ class Pluto(SDR):
         self.tx_buffer_size = buffer_size
 
     def close(self):
+        if not hasattr(self, "radio"):
+            return
         if self.radio.tx_cyclic_buffer:
             self.radio.tx_destroy_buffer()
         del self.radio
diff --git a/src/ria_toolkit_oss/server/routers/inference.py b/src/ria_toolkit_oss/server/routers/inference.py
index 83ae705..2c7b5c7 100644
--- a/src/ria_toolkit_oss/server/routers/inference.py
+++ b/src/ria_toolkit_oss/server/routers/inference.py
@@ -103,6 +103,7 @@ def _inference_loop(state: InferenceState, sdr) -> None:
     from ria_toolkit_oss.orchestration.qa import estimate_snr_db
 
     state.sdr = sdr
+    state.set_running(True)
     session = state.session
     input_name = session.get_inputs()[0].name
     expected_shape = tuple(
@@ -189,7 +190,7 @@ async def start_inference(request: StartInferenceRequest):
 
     try:
         from ria_toolkit_oss.orchestration.executor import _DEVICE_ALIASES
-        from ria_toolkit_oss_cli.ria_toolkit_oss.common import get_sdr_device
+        from ria_toolkit_oss.sdr import get_sdr_device
     except ImportError as e:
         raise HTTPException(status_code=status.HTTP_503_SERVICE_UNAVAILABLE, detail=f"SDR import failed: {e}")
 
@@ -207,7 +208,6 @@ async def start_inference(request: StartInferenceRequest):
         raise HTTPException(status_code=status.HTTP_422_UNPROCESSABLE_ENTITY, detail=f"SDR initialisation failed: {e}")
 
     state.stop_event.clear()
-    state.set_running(True)
     state.thread = threading.Thread(target=_inference_loop, args=(state, sdr), daemon=True)
     state.thread.start()
     return StartInferenceResponse(running=True)
diff --git a/src/ria_toolkit_oss/server/routers/orchestrator.py b/src/ria_toolkit_oss/server/routers/orchestrator.py
index 5257561..dfc01af 100644
--- a/src/ria_toolkit_oss/server/routers/orchestrator.py
+++ b/src/ria_toolkit_oss/server/routers/orchestrator.py
@@ -67,7 +67,7 @@ async def deploy(request: DeployRequest):
     except (ValueError, KeyError) as e:
         raise HTTPException(status_code=status.HTTP_422_UNPROCESSABLE_ENTITY, detail=str(e))
 
-    if any(t.script for t in cfg.transmitters):
+    if cfg.transmitters and any(t.script for t in cfg.transmitters):
         raise HTTPException(
             status_code=status.HTTP_422_UNPROCESSABLE_ENTITY,
             detail="External scripts are not permitted in server-deployed campaigns. "
diff --git a/src/ria_toolkit_oss/signal/basic_signal_generator.py b/src/ria_toolkit_oss/signal/basic_signal_generator.py
index 067d85a..1f42b9a 100644
--- a/src/ria_toolkit_oss/signal/basic_signal_generator.py
+++ b/src/ria_toolkit_oss/signal/basic_signal_generator.py
@@ -2,6 +2,7 @@
 .. todo:: Need to add some information here about signal generation and the signal generators in this module.
 """
 
+import warnings
 from typing import Optional
 
 import numpy as np
@@ -227,7 +228,7 @@ def noise(
 
     # TODO figure out a better way to make it conform to [-1,1]
     if not np.array_equal(magnitude, magnitude2):
-        print("Warning: clipping in basic_signal_generator.noise")
+        warnings.warn("basic_signal_generator.noise: magnitude clipped to [-1, 1]")
 
     phase = np.random.uniform(low=0, high=2 * np.pi, size=length)
     complex_awgn = magnitude2 * np.exp(1j * phase)
@@ -268,6 +269,9 @@ def chirp(sample_rate: int, num_samples: int, center_frequency: Optional[float]
     .. todo:: Usage examples coming soon!
     """
     # Ensure that the generated chirp signal remains within a safe frequency range to avoid aliasing.
+    if num_samples < 2:
+        raise ValueError("num_samples must be >= 2 for chirp generation")
+
     chirp_start_frequency = center_frequency - sample_rate / 4
     chirp_end_frequency = center_frequency + sample_rate / 4
 
@@ -307,6 +311,9 @@ def lfm_chirp_complex(
         down_part = np.flip(up_part)
         baseband_chirp = np.concatenate([up_part, down_part])
 
+    else:
+        raise ValueError(f"Unknown chirp_type '{chirp_type}'. Must be 'up', 'down', or 'up_down'.")
+
     # Generate the full signal by tiling the windowed chirp
     num_chirps = round(total_time / chirp_period)
     full_signal = np.tile(baseband_chirp, num_chirps)
diff --git a/src/ria_toolkit_oss/transforms/iq_impairments.py b/src/ria_toolkit_oss/transforms/iq_impairments.py
index a93ca36..34a6eb0 100644
--- a/src/ria_toolkit_oss/transforms/iq_impairments.py
+++ b/src/ria_toolkit_oss/transforms/iq_impairments.py
@@ -204,7 +204,7 @@ def phase_shift(signal: ArrayLike | Recording, phase: Optional[float] = np.pi) -
     >>> rec = Recording(data=[[1+1j, 2+2j, 3+3j, 4+4j]])
     >>> new_rec = phase_shift(rec, np.pi/2)
     >>> new_rec.data
-    array([[-1+1j, -2+2j -3+3j -4+4j]])
+    array([[-1+1j, -2+2j, -3+3j, -4+4j]])
     """
     # TODO: Additional info needs to be added to docstring description
 
diff --git a/src/ria_toolkit_oss_cli/ria_toolkit_oss/capture.py b/src/ria_toolkit_oss_cli/ria_toolkit_oss/capture.py
index 5c61600..ea1ccd7 100644
--- a/src/ria_toolkit_oss_cli/ria_toolkit_oss/capture.py
+++ b/src/ria_toolkit_oss_cli/ria_toolkit_oss/capture.py
@@ -315,7 +315,7 @@ def capture(
     ident = ident or config.get("ident") or config.get("serial")  # Support legacy 'serial' in config
     sample_rate = sample_rate or config.get("sample_rate")
     center_frequency = center_frequency or config.get("center_frequency")
-    gain = gain or config.get("gain")
+    gain = gain if gain is not None else config.get("gain")
     bandwidth = bandwidth or config.get("bandwidth")
     num_samples = num_samples or config.get("num_samples")
     duration = duration or config.get("duration")
diff --git a/src/ria_toolkit_oss_cli/ria_toolkit_oss/generate.py b/src/ria_toolkit_oss_cli/ria_toolkit_oss/generate.py
index f2e14ba..fb6d92c 100644
--- a/src/ria_toolkit_oss_cli/ria_toolkit_oss/generate.py
+++ b/src/ria_toolkit_oss_cli/ria_toolkit_oss/generate.py
@@ -214,7 +214,7 @@ def apply_post_processing(
         )
 
     # 3. AWGN (Final stage usually)
-    if add_noise == "awgn":
+    if add_noise:
         npow = channel_params.get("noise_power", 0.1)
         echo_verbose(f"Applying AWGN (Power={npow})", verbose)
 
diff --git a/src/ria_toolkit_oss_cli/ria_toolkit_oss/transmit.py b/src/ria_toolkit_oss_cli/ria_toolkit_oss/transmit.py
index f411a0b..12c3aea 100644
--- a/src/ria_toolkit_oss_cli/ria_toolkit_oss/transmit.py
+++ b/src/ria_toolkit_oss_cli/ria_toolkit_oss/transmit.py
@@ -393,7 +393,7 @@ def transmit(
     ident = ident or config.get("ident") or config.get("serial")  # Support legacy 'serial' in config
     sample_rate = sample_rate or config.get("sample_rate")
     center_frequency = center_frequency or config.get("center_frequency")
-    gain = gain or config.get("gain")
+    gain = gain if gain is not None else config.get("gain")
     bandwidth = bandwidth or config.get("bandwidth")
     input_file = input_file or config.get("input")
     generate = generate or config.get("generate")
diff --git a/tests/transforms/test_iq_augmentations.py b/tests/transforms/test_iq_augmentations.py
index 5f19acf..7a12024 100644
--- a/tests/transforms/test_iq_augmentations.py
+++ b/tests/transforms/test_iq_augmentations.py
@@ -207,7 +207,7 @@ def test_cut_out_avg_snr_1():
     transformed_data = iq_augmentations.cut_out(TEST_DATA1, max_section_size=2, fill_type="avg-snr")
     assert np.allclose(
         transformed_data,
-        np.asarray([[-1.26516288 - 0.36655702j, -2.44693984 + 1.27294267j, 3 + 3j, 4.1583403 - 0.96625365j]]),
+        np.asarray([[1.04504475 - 3.19650874j, 2.18835276 + 1.87922077j, 3 + 3j, 3.38706877 - 0.53958902j]]),
     )
 
 
@@ -334,7 +334,7 @@ def test_drop_samples_invalid_real_raises():
 
 def test_quantize_tape_invalid_rounding_type_raises():
     # An unrecognised rounding_type must raise UserWarning.
-    with pytest.raises(UserWarning):
+    with pytest.warns(UserWarning):
         iq_augmentations.quantize_tape(TEST_DATA1, rounding_type="round")
 
 
@@ -347,7 +347,7 @@ def test_quantize_tape_invalid_real_raises():
 
 
 def test_quantize_parts_invalid_rounding_type_raises():
-    with pytest.raises(UserWarning):
+    with pytest.warns(UserWarning):
         iq_augmentations.quantize_parts(TEST_DATA1, rounding_type="round")
 
 
@@ -399,7 +399,7 @@ def test_cut_out_rec_input():
 
 
 def test_cut_out_invalid_fill_type_raises():
-    with pytest.raises(UserWarning):
+    with pytest.warns(UserWarning):
         iq_augmentations.cut_out(TEST_DATA1, max_section_size=2, fill_type="bad")
 
 
diff --git a/tests/transforms/test_iq_impairments.py b/tests/transforms/test_iq_impairments.py
index f685151..a5c5a4b 100644
--- a/tests/transforms/test_iq_impairments.py
+++ b/tests/transforms/test_iq_impairments.py
@@ -130,23 +130,14 @@ def test_time_shift_invalid_real_input():
 
 def test_time_shift_large_shift_warns():
     """shift > n raises a UserWarning."""
-    with pytest.raises(UserWarning):
+    with pytest.warns(UserWarning):
         iq_impairments.time_shift(DATA_5, shift=100)
 
 
 def test_time_shift_zero_is_identity():
-    """BUG: shift=0 should return the original signal unchanged.
-
-    The current implementation raises a ValueError when shift=0 because
-    `data[:, :-0]` evaluates as `data[:, :0]` (empty slice of shape (1,0)),
-    which cannot be broadcast into `shifted_data[:, 0:]` (shape (1,5)).
-
-    This test documents the bug: callers cannot safely pass shift=0.
-    Remove the `pytest.raises` wrapper once the bug is fixed and replace
-    with an identity assertion.
-    """
-    with pytest.raises((ValueError, AssertionError), match=".*"):
-        iq_impairments.time_shift(DATA_5, shift=0)
+    """shift=0 returns the original signal unchanged."""
+    result = iq_impairments.time_shift(DATA_5, shift=0)
+    assert np.array_equal(result, DATA_5)
 
 
 # ---------------------------------------------------------------------------
@@ -408,17 +399,8 @@ def test_resample_invalid_real_input():
         iq_impairments.resample(real_data)
 
 
-def test_resample_downsample_returns_shorter_array():
-    """BUG documentation: up=1, down=2 returns a shorter array instead of zero-padding.
-
-    The 'else' branch of resample() builds 'empty_array' but never returns it.
-    The shorter resampled_iqdata is returned directly. This test documents the
-    actual (potentially unintended) behaviour so any future fix is detectable.
-    """
+def test_resample_downsample_returns_same_length():
+    """Downsampling zero-pads output to match input length."""
     signal = np.array([[1 + 1j, 2 + 2j, 3 + 3j, 4 + 4j, 5 + 5j, 6 + 6j]], dtype=np.complex128)
     result = iq_impairments.resample(signal, up=1, down=2)
-    # Downsampling by 2 produces ~3 samples; the empty_array logic is dead code.
-    assert result.shape[1] < signal.shape[1], (
-        "resample with up<down should return fewer samples than the input "
-        "(empty_array is built but discarded — dead code)."
-    )
+    assert result.shape[1] == signal.shape[1]