diff --git a/tuner/tuner/libtuner.py b/tuner/tuner/libtuner.py
index 91c7b417a..3aa932dc4 100644
--- a/tuner/tuner/libtuner.py
+++ b/tuner/tuner/libtuner.py
@@ -38,7 +38,7 @@
 import random
 import json
 from abc import ABC, abstractmethod
-import iree.runtime as ireert
+import iree.runtime as ireert  # type: ignore
 from . import candidate_gen
 
 
@@ -250,10 +250,11 @@ def get_mean_time_us(self) -> Optional[float]:
         mean_benchmark = self.find_mean_benchmark(self.result_json)
 
         if mean_benchmark:
-            real_time = mean_benchmark.get("real_time")
-            time_unit = mean_benchmark.get("time_unit")
+            real_time: float | None = mean_benchmark.get("real_time")
+            time_unit: str | None = mean_benchmark.get("time_unit")
 
             if real_time is not None:
+                assert time_unit is not None
                 return self.unit_to_microseconds(real_time, time_unit)
 
         return None
@@ -549,7 +550,7 @@ def create_worker_context_queue(device_ids: list[int]) -> queue.Queue[tuple[int,
     return worker_contexts_queue
 
 
-def run_command(run_pack: RunPack) -> TaskResult:
+def run_command(run_pack: RunPack) -> RunResult:
     command = run_pack.command
     check = run_pack.check
     timeout_seconds = run_pack.timeout_seconds
@@ -946,6 +947,7 @@ def parse_dispatch_benchmark_results(
             continue
 
         res_json = extract_benchmark_from_run_result(benchmark_result.run_result)
+        assert res_json is not None
         res = IREEBenchmarkResult(candidate_id, res_json)
         benchmark_time = res.get_mean_time_us()
         assert benchmark_time is not None
@@ -985,7 +987,10 @@ def generate_sample_task_result(
         stdout=stdout,
         returncode=0,
     )
-    return TaskResult(result=res, candidate_id=candidate_id, device_id=device_id)
+    run_result = RunResult(res, False)
+    return TaskResult(
+        run_result=run_result, candidate_id=candidate_id, device_id=device_id
+    )
 
 
 def generate_dryrun_dispatch_benchmark_results(
@@ -1235,6 +1240,7 @@ def parse_model_benchmark_results(
                 continue
 
             result_json = extract_benchmark_from_run_result(task_result.run_result)
+            assert result_json is not None
             res = IREEBenchmarkResult(candidate_id, result_json)
             benchmark_time = res.get_mean_time_us()
             assert benchmark_time is not None
diff --git a/tuner/tuner/libtuner_test.py b/tuner/tuner/libtuner_test.py
index 36bda3bd5..11af59af4 100644
--- a/tuner/tuner/libtuner_test.py
+++ b/tuner/tuner/libtuner_test.py
@@ -7,6 +7,7 @@
 import argparse
 import pytest
 import json
+from subprocess import CompletedProcess
 from unittest.mock import call, patch, MagicMock
 from . import libtuner
 
@@ -15,15 +16,15 @@
 """
 
 
-def test_group_benchmark_results_by_device_id():
+def test_group_benchmark_results_by_device_id() -> None:
     # Create mock TaskResult objects with device_id attributes
-    task_result_1 = MagicMock()
+    task_result_1: libtuner.TaskResult = MagicMock(spec=libtuner.TaskResult)
     task_result_1.device_id = "device_1"
 
-    task_result_2 = MagicMock()
+    task_result_2: libtuner.TaskResult = MagicMock(spec=libtuner.TaskResult)
     task_result_2.device_id = "device_2"
 
-    task_result_3 = MagicMock()
+    task_result_3: libtuner.TaskResult = MagicMock(spec=libtuner.TaskResult)
     task_result_3.device_id = "device_1"
 
     benchmark_results = [task_result_1, task_result_2, task_result_3]
@@ -40,7 +41,7 @@ def test_group_benchmark_results_by_device_id():
     assert grouped_results[1][0].device_id == "device_2"
 
 
-def test_find_collisions():
+def test_find_collisions() -> None:
     input = [(1, "abc"), (2, "def"), (3, "abc")]
     assert libtuner.find_collisions(input) == (True, [("abc", [1, 3]), ("def", [2])])
     input = [(1, "abc"), (2, "def"), (3, "hig")]
@@ -50,14 +51,14 @@ def test_find_collisions():
     )
 
 
-def test_collision_handler():
+def test_collision_handler() -> None:
     input = [(1, "abc"), (2, "def"), (3, "abc"), (4, "def"), (5, "hig")]
     assert libtuner.collision_handler(input) == (True, [1, 2, 5])
     input = [(1, "abc"), (2, "def"), (3, "hig")]
     assert libtuner.collision_handler(input) == (False, [])
 
 
-def test_IREEBenchmarkResult_get():
+def test_IREEBenchmarkResult_get() -> None:
     # Time is int in us
     int_json = [{"aggregate_name": "mean", "real_time": 1, "time_unit": "us"}]
 
@@ -108,7 +109,7 @@ def test_IREEBenchmarkResult_get():
     assert res.get_mean_time_us() == None
 
     # Invalid json: empty dictionary
-    res = libtuner.IREEBenchmarkResult(candidate_id=8, result_json={})
+    res = libtuner.IREEBenchmarkResult(candidate_id=8, result_json=[])
     assert res.get_mean_time_us() is None
 
     # Invalid json: invalid time unit
@@ -131,7 +132,7 @@ def test_IREEBenchmarkResult_get():
     assert res.get_mean_time_us() is None
 
 
-def test_generate_display_BR():
+def test_generate_display_BR() -> None:
     output = libtuner.generate_display_DBR(1, 3.14)
     expected = f"1\tMean Time: 3.1"
     assert output == expected, "DispatchBenchmarkResult generates invalid sample string"
@@ -147,29 +148,38 @@ def test_generate_display_BR():
     assert output == expected, "ModelBenchmarkResult generates invalid sample string"
 
 
-def test_parse_dispatch_benchmark_results():
+def make_mock_task_result() -> libtuner.TaskResult:
+    process: CompletedProcess = MagicMock(spec=CompletedProcess)
+    run_result = libtuner.RunResult(process, False)
+    task_result = libtuner.TaskResult(run_result, 0, "")
+    return task_result
+
+
+def test_parse_dispatch_benchmark_results() -> None:
     base_path = libtuner.Path("/mock/base/dir")
     spec_dir = base_path / "specs"
     path_config = libtuner.PathConfig()
     object.__setattr__(path_config, "specs_dir", spec_dir)
 
-    mock_result_1 = MagicMock()
+    mock_result_1 = make_mock_task_result()
     mock_json_1 = {
         "benchmarks": [
             {"aggregate_name": "mean", "real_time": 100.0, "time_unit": "us"}
         ]
     }
+    assert mock_result_1.run_result.process_res is not None
     mock_result_1.run_result.process_res.stdout = json.dumps(mock_json_1)
     mock_result_1.candidate_id = 1
-    mock_result_2 = MagicMock()
+    mock_result_2 = make_mock_task_result()
     mock_json_2 = {
         "benchmarks": [
             {"aggregate_name": "mean", "real_time": 200.0, "time_unit": "us"}
         ]
     }
+    assert mock_result_2.run_result.process_res is not None
     mock_result_2.run_result.process_res.stdout = json.dumps(mock_json_2)
     mock_result_2.candidate_id = 2
-    mock_result_3 = MagicMock()
+    mock_result_3 = make_mock_task_result()
     mock_json_3 = {
         "benchmarks": [
             {
@@ -179,11 +189,11 @@ def test_parse_dispatch_benchmark_results():
             }
         ]
     }
+    assert mock_result_3.run_result.process_res is not None
     mock_result_3.run_result.process_res.stdout = json.dumps(mock_json_3)
     mock_result_3.candidate_id = 3
-    mock_result_4 = MagicMock()
-    mock_result_4.run_result.process_res = None  # Incomplete result
-    mock_result_4.candidate_id = 4
+    # Incomplete result.
+    mock_result_4 = libtuner.TaskResult(libtuner.RunResult(None, True), 4, "4")
     benchmark_results = [mock_result_1, mock_result_2, mock_result_3, mock_result_4]
 
     candidate_trackers = []
@@ -239,7 +249,7 @@ def test_parse_dispatch_benchmark_results():
     )
 
 
-def test_parse_model_benchmark_results():
+def test_parse_model_benchmark_results() -> None:
     # Setup mock data for candidate_trackers
     tracker0 = libtuner.CandidateTracker(0)
     tracker0.compiled_model_path = libtuner.Path("/path/to/baseline.vmfb")
@@ -256,38 +266,40 @@ def test_parse_model_benchmark_results():
     candidate_trackers = [tracker0, tracker1, tracker2, tracker3]
 
     # Setup mock data for task results
-    result1 = MagicMock()
+    result1 = make_mock_task_result()
     result_json_1 = {"benchmarks": [{"real_time": 1.23}]}
+    assert result1.run_result.process_res is not None
     result1.run_result.process_res.stdout = json.dumps(result_json_1)
     result1.candidate_id = 1
     result1.device_id = "device1"
 
-    result2 = MagicMock()
+    result2 = make_mock_task_result()
     result_json_2 = {"benchmarks": [{"real_time": 4.56}]}
+    assert result2.run_result.process_res is not None
     result2.run_result.process_res.stdout = json.dumps(result_json_2)
     result2.candidate_id = 2
     result2.device_id = "device2"
 
-    result3 = MagicMock()
+    result3 = make_mock_task_result()
     result_json_3 = {"benchmarks": [{"real_time": 0.98}]}
+    assert result3.run_result.process_res is not None
     result3.run_result.process_res.stdout = json.dumps(result_json_3)
     result3.candidate_id = 0
     result3.device_id = "device1"
 
-    result4 = MagicMock()
+    result4 = make_mock_task_result()
     result_json_4 = {"benchmarks": [{"real_time": 4.13}]}
+    assert result4.run_result.process_res is not None
     result4.run_result.process_res.stdout = json.dumps(result_json_4)
     result4.candidate_id = 0
     result4.device_id = "device2"
 
     # Incomplete baseline on device3
-    result5 = MagicMock()
-    result5.run_result.process_res = None
-    result5.candidate_id = 0
-    result5.device_id = "device3"
+    result5 = libtuner.TaskResult(libtuner.RunResult(None, True), 0, "device3")
 
-    result6 = MagicMock()
+    result6 = make_mock_task_result()
     result_json_6 = {"benchmarks": [{"real_time": 3.38}]}
+    assert result6.run_result.process_res is not None
     result6.run_result.process_res.stdout = json.dumps(result_json_6)
     result6.candidate_id = 3
     result6.device_id = "device3"
@@ -347,14 +359,14 @@ def mock_get_mean_time_us(self):
             )
 
 
-def test_extract_driver_names():
+def test_extract_driver_names() -> None:
     user_devices = ["hip://0", "local-sync://default", "cuda://default"]
     expected_output = {"hip", "local-sync", "cuda"}
 
     assert libtuner.extract_driver_names(user_devices) == expected_output
 
 
-def test_fetch_available_devices_success():
+def test_fetch_available_devices_success() -> None:
     drivers = ["hip", "local-sync", "cuda"]
     mock_devices = {
         "hip": [{"path": "ABCD", "device_id": 1}],
@@ -384,7 +396,7 @@ def get_mock_driver(name):
         assert actual_output == expected_output
 
 
-def test_fetch_available_devices_failure():
+def test_fetch_available_devices_failure() -> None:
     drivers = ["hip", "local-sync", "cuda"]
     mock_devices = {
         "hip": [{"path": "ABCD", "device_id": 1}],
@@ -421,7 +433,7 @@ def get_mock_driver(name):
             )
 
 
-def test_parse_devices():
+def test_parse_devices() -> None:
     user_devices_str = "hip://0, local-sync://default, cuda://default"
     expected_output = ["hip://0", "local-sync://default", "cuda://default"]
 
@@ -432,7 +444,7 @@ def test_parse_devices():
         mock_handle_error.assert_not_called()
 
 
-def test_parse_devices_with_invalid_input():
+def test_parse_devices_with_invalid_input() -> None:
     user_devices_str = "hip://0, local-sync://default, invalid_device, cuda://default"
     expected_output = [
         "hip://0",
@@ -452,7 +464,7 @@ def test_parse_devices_with_invalid_input():
         )
 
 
-def test_validate_devices():
+def test_validate_devices() -> None:
     user_devices = ["hip://0", "local-sync://default"]
     user_drivers = {"hip", "local-sync"}
 
@@ -469,7 +481,7 @@ def test_validate_devices():
                 )
 
 
-def test_validate_devices_with_invalid_device():
+def test_validate_devices_with_invalid_device() -> None:
     user_devices = ["hip://0", "local-sync://default", "cuda://default"]
     user_drivers = {"hip", "local-sync", "cuda"}