diff --git a/docs/getting_started/quickstart.ipynb b/docs/getting_started/quickstart.ipynb
index d9a9de3..daf9cfe 100644
--- a/docs/getting_started/quickstart.ipynb
+++ b/docs/getting_started/quickstart.ipynb
@@ -477,8 +477,8 @@
     }
    ],
    "source": [
-    "first_result = [row[0] for row in result[\"results\"]]\n",
-    "second_result = [row[1] for row in result[\"results\"]]\n",
+    "first_result = [row[0] for row in result[\"result\"]]\n",
+    "second_result = [row[1] for row in result[\"result\"]]\n",
     "\n",
     "print(first_result.count(None))\n",
     "print(second_result.count(None))"
diff --git a/fastrepl/runner.py b/fastrepl/runner.py
index b35d713..e4965de 100644
--- a/fastrepl/runner.py
+++ b/fastrepl/runner.py
@@ -24,17 +24,26 @@ def __init__(
         evaluator: fastrepl.Evaluator,
         dataset: Dataset,
         output_feature="result",
-        output_feature_multiple="results",
     ) -> None:
         self._evaluator = evaluator
         self._dataset = dataset
 
-        self._output_feature = output_feature
-        self._output_feature_multiple = output_feature_multiple
-
         self._input_features = [
             param for param in inspect.signature(evaluator.run).parameters.keys()
         ]
+        self._output_feature = output_feature
+
+    def _validate(
+        self,
+        evaluator: fastrepl.Evaluator,
+        dataset: Dataset,
+    ) -> None:
+        if any(feature not in dataset.column_names for feature in self._input_features):
+            eval_name = type(evaluator).__name__
+
+            raise ValueError(  # TODO: custom error
+                f"{eval_name} requires {self._input_features}, but the provided dataset has {dataset.column_names}"
+            )
 
     def _run_eval(self, **kwargs) -> Optional[Any]:
         return self._evaluator.run(**kwargs)
@@ -62,24 +71,19 @@ def _run(self, progress: Progress, task_id: TaskID) -> List[Optional[Any]]:
         return results
 
     def run(self, num=1) -> Dataset:
+        self._validate(self._evaluator, self._dataset)
+
         with Progress() as progress:
             msg = "[cyan]Processing..."
             task_id = progress.add_task(msg, total=len(self._dataset) * num)
 
-            if num == 1:
-                result = self._run(progress, task_id)
-
-                return self._dataset.add_column(
-                    self._output_feature,
-                    result,
-                )
-            else:
+            if num > 1:
                 results = [self._run(progress, task_id) for _ in range(num)]
+                column = list(zip(*results))
+                return self._dataset.add_column(self._output_feature, column)
 
-                return self._dataset.add_column(
-                    self._output_feature_multiple,
-                    list(zip(*results)),
-                )
+            column = self._run(progress, task_id)
+            return self._dataset.add_column(self._output_feature, column)
 
 
 class LocalRunnerREPL(LocalRunner):
diff --git a/tests/unit/test_runner.py b/tests/unit/test_runner.py
index 33faf80..81c0ea8 100644
--- a/tests/unit/test_runner.py
+++ b/tests/unit/test_runner.py
@@ -1,5 +1,4 @@
 import pytest
-import warnings
 from datasets import Dataset
 
 import fastrepl
@@ -19,40 +18,49 @@ def mock_run(*args, **kwargs):
 
 
 class TestLocalRunner:
-    def test_runner_num_1(self, mock_runs):
+    def test_num_1(self, mock_runs):
         mock_runs([[1]])
 
-        ds = Dataset.from_dict({"input": [1]})
+        ds = Dataset.from_dict({"sample": [1]})
         eval = fastrepl.SimpleEvaluator(
             node=fastrepl.LLMClassificationHead(context="", labels={})
         )
 
         result = fastrepl.LocalRunner(evaluator=eval, dataset=ds).run(num=1)
 
-        assert result.column_names == ["input", "result"]
+        assert result.column_names == ["sample", "result"]
 
-    def test_runner_num_2(self, mock_runs):
+    def test_num_2(self, mock_runs):
         mock_runs([[1, 2, 3, 4], [1, 2, 3, 5]])
 
-        ds = Dataset.from_dict({"input": [1, 2, 3, 4]})
+        ds = Dataset.from_dict({"sample": [1, 2, 3, 4]})
         eval = fastrepl.SimpleEvaluator(
             node=fastrepl.LLMClassificationHead(context="", labels={})
         )
 
         result = fastrepl.LocalRunner(evaluator=eval, dataset=ds).run(num=2)
 
-        assert result.column_names == ["input", "results"]
-        assert result["results"] == [[1, 1], [2, 2], [3, 3], [4, 5]]
+        assert result.column_names == ["sample", "result"]
+        assert result["result"] == [[1, 1], [2, 2], [3, 3], [4, 5]]
 
-    def test_runner_num_2_handle_none(self, mock_runs):
+    def test_num_2_handle_none(self, mock_runs):
         mock_runs([[1, 2, 3, 4], [1, 2, 3, None]])
 
-        ds = Dataset.from_dict({"input": [1, 2, 3, 4]})
+        ds = Dataset.from_dict({"sample": [1, 2, 3, 4]})
         eval = fastrepl.SimpleEvaluator(
             node=fastrepl.LLMClassificationHead(context="", labels={})
         )
 
         result = fastrepl.LocalRunner(evaluator=eval, dataset=ds).run(num=2)
 
-        assert result.column_names == ["input", "results"]
-        assert result["results"] == [[1, 1], [2, 2], [3, 3], [4, None]]
+        assert result.column_names == ["sample", "result"]
+        assert result["result"] == [[1, 1], [2, 2], [3, 3], [4, None]]
+
+    def test_validation(self):
+        ds = Dataset.from_dict({"input": [1, 2, 3, 4]})
+        eval = fastrepl.SimpleEvaluator(
+            node=fastrepl.LLMClassificationHead(context="", labels={})
+        )
+
+        with pytest.raises(ValueError):
+            fastrepl.LocalRunner(evaluator=eval, dataset=ds).run()