diff --git a/fuzzer_runner/pyproject.toml b/fuzzer_runner/pyproject.toml
index 242af9f1..efc21d0d 100644
--- a/fuzzer_runner/pyproject.toml
+++ b/fuzzer_runner/pyproject.toml
@@ -9,6 +9,7 @@ dependencies = [
     "common",
     "clusterfuzz ==2.6.0",
     "pydantic ~=2.11.7",
+    "setuptools",  # Required for pkg_resources used by google-cloud-ndb (clusterfuzz dep)
 ]
 
 [project.urls]
diff --git a/fuzzer_runner/tests/test_fuzzer.py b/fuzzer_runner/tests/test_fuzzer.py
deleted file mode 100644
index 4b9095b6..00000000
--- a/fuzzer_runner/tests/test_fuzzer.py
+++ /dev/null
@@ -1,2 +0,0 @@
-def test_empty():
-    pass
diff --git a/fuzzer_runner/tests/test_runner.py b/fuzzer_runner/tests/test_runner.py
new file mode 100644
index 00000000..8b1bc4e8
--- /dev/null
+++ b/fuzzer_runner/tests/test_runner.py
@@ -0,0 +1,83 @@
+"""Tests for the fuzzer runner module."""
+
+from unittest.mock import MagicMock, patch
+
+from buttercup.fuzzer_runner.runner import Conf, Runner
+
+
+class TestRunner:
+    """Tests for the Runner class."""
+
+    @patch("buttercup.fuzzer_runner.runner.patched_temp_dir")
+    @patch("buttercup.fuzzer_runner.runner.scratch_cwd")
+    @patch("os.makedirs")
+    def test_run_fuzzer_initializes_engine(self, mock_makedirs, mock_scratch_cwd, mock_patched_temp_dir):
+        """Test run_fuzzer"""
+        from buttercup.common.types import FuzzConfiguration
+        from clusterfuzz._internal.bot.fuzzers.libFuzzer import engine as libfuzzer_engine
+
+        mock_patched_temp_dir.return_value.__enter__ = MagicMock()
+        mock_patched_temp_dir.return_value.__exit__ = MagicMock(return_value=False)
+        mock_scratch_cwd.return_value.__enter__ = MagicMock()
+        mock_scratch_cwd.return_value.__exit__ = MagicMock(return_value=False)
+
+        # Mock the engine methods that would fail without a real fuzzer binary
+        mock_opts = MagicMock()
+        mock_opts.corpus_dir = "/corpus"
+        mock_opts.arguments = []
+        mock_opts.strategies = []
+
+        mock_result = MagicMock()
+        mock_result.crashes = []
+        mock_result.logs = "test"
+        mock_result.stats = {}
+        mock_result.time_executed = 1.0
+        mock_result.timed_out = False
+
+        with (
+            patch.object(libfuzzer_engine.Engine, "prepare", return_value=mock_opts),
+            patch.object(libfuzzer_engine.Engine, "fuzz", return_value=mock_result),
+        ):
+            conf = Conf(timeout=60)
+            runner = Runner(conf)
+            fuzzconf = FuzzConfiguration(
+                corpus_dir="/corpus",
+                target_path="/target",
+                engine="libfuzzer",
+                sanitizer="address",
+            )
+
+            result = runner.run_fuzzer(fuzzconf)
+
+            assert result.crashes == []
+            assert result.timed_out is False
+
+    @patch("buttercup.fuzzer_runner.runner.scratch_dir")
+    @patch("buttercup.fuzzer_runner.runner.patched_temp_dir")
+    @patch("buttercup.fuzzer_runner.runner.scratch_cwd")
+    def test_merge_corpus_initializes_engine(self, mock_scratch_cwd, mock_patched_temp_dir, mock_scratch_dir):
+        """Test merge_corpus."""
+        from buttercup.common.types import FuzzConfiguration
+        from clusterfuzz._internal.bot.fuzzers.libFuzzer import engine as libfuzzer_engine
+
+        mock_patched_temp_dir.return_value.__enter__ = MagicMock()
+        mock_patched_temp_dir.return_value.__exit__ = MagicMock(return_value=False)
+        mock_scratch_cwd.return_value.__enter__ = MagicMock()
+        mock_scratch_cwd.return_value.__exit__ = MagicMock(return_value=False)
+
+        mock_td = MagicMock()
+        mock_td.path = "/tmp/scratch"
+        mock_scratch_dir.return_value.__enter__ = MagicMock(return_value=mock_td)
+        mock_scratch_dir.return_value.__exit__ = MagicMock(return_value=False)
+
+        with patch.object(libfuzzer_engine.Engine, "minimize_corpus"):
+            conf = Conf(timeout=60)
+            runner = Runner(conf)
+            fuzzconf = FuzzConfiguration(
+                corpus_dir="/corpus",
+                target_path="/target",
+                engine="libfuzzer",
+                sanitizer="address",
+            )
+
+            runner.merge_corpus(fuzzconf, "/output")
diff --git a/fuzzer_runner/uv.lock b/fuzzer_runner/uv.lock
index 4ba3cc5b..3167ebf4 100644
--- a/fuzzer_runner/uv.lock
+++ b/fuzzer_runner/uv.lock
@@ -264,6 +264,7 @@ dependencies = [
     { name = "clusterfuzz" },
     { name = "common" },
     { name = "pydantic" },
+    { name = "setuptools" },
 ]
 
 [package.dev-dependencies]
@@ -281,6 +282,7 @@ requires-dist = [
     { name = "clusterfuzz", specifier = "==2.6.0" },
     { name = "common", editable = "../common" },
     { name = "pydantic", specifier = "~=2.11.7" },
+    { name = "setuptools" },
 ]
 
 [package.metadata.requires-dev]
@@ -1252,6 +1254,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/9e/6a/40fee331a52339926a92e17ae748827270b288a35ef4a15c9c8f2ec54715/ruff-0.14.14-py3-none-win_arm64.whl", hash = "sha256:56e6981a98b13a32236a72a8da421d7839221fa308b223b9283312312e5ac76c", size = 10920448, upload-time = "2026-01-22T22:30:15.417Z" },
 ]
 
+[[package]]
+name = "setuptools"
+version = "80.10.2"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/76/95/faf61eb8363f26aa7e1d762267a8d602a1b26d4f3a1e758e92cb3cb8b054/setuptools-80.10.2.tar.gz", hash = "sha256:8b0e9d10c784bf7d262c4e5ec5d4ec94127ce206e8738f29a437945fbc219b70", size = 1200343, upload-time = "2026-01-25T22:38:17.252Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/94/b8/f1f62a5e3c0ad2ff1d189590bfa4c46b4f3b6e49cef6f26c6ee4e575394d/setuptools-80.10.2-py3-none-any.whl", hash = "sha256:95b30ddfb717250edb492926c92b5221f7ef3fbcc2b07579bcd4a27da21d0173", size = 1064234, upload-time = "2026-01-25T22:38:15.216Z" },
+]
+
 [[package]]
 name = "six"
 version = "1.17.0"