Add CLI tests

CHANGELOG.md

@@ -96,6 +96,8 @@
   - Added focused tests for empty threshold iterables, mixed `None` threshold groups in dict mode, and explicit all-`None` threshold handling across return formats.
 - **Expanded IPW diagnostics coverage for fit-parameter reporting**
   - Refactored diagnostics tests to use a shared IPW setup helper (removing repeated fixture construction), added edge-case assertions for filtered non-string solver/penalty values and NaN coercion of non-scalar `tol`/`l1_ratio` inputs, and now assert solver/penalty labels match fitted model parameters.
+- **Added unit coverage for CLI I/O and empty-batch handling**
+  - Added focused tests for `BalanceCLI.process_batch()` empty-sample failure payloads, `load_and_check_input()` CSV loading paths, and `write_outputs()` delimiter-aware output writing for both adjusted and diagnostics files.
 
 # 0.16.0 (2026-02-09)
 

balance/cli.py

@@ -667,7 +667,6 @@ def process_batch(
                 set(result.keys()) == {"adjusted", "diagnostics"}
                 # True
         """
-        # TODO: add unit tests
         sample_df, target_df = self.split_sample(batch_df)
 
         if sample_df.shape[0] == 0:
@@ -890,7 +889,6 @@ def load_and_check_input(self) -> pd.DataFrame:
                     loaded.shape
                     # (1, 2)
         """
-        # TODO: Add unit tests for function
         # Load and check input
         input_df = pd.read_csv(self.args.input_file, sep=self.args.sep_input_file)
         logger.info("Number of rows in input file: %d" % input_df.shape[0])
@@ -932,7 +930,6 @@ def write_outputs(
                 )
                 cli.write_outputs(output_df, diagnostics_df)
         """
-        # TODO: Add unit tests for function
         # Write output
         output_df.to_csv(
             path_or_buf=self.args.output_file,

tests/test_cli.py

@@ -278,6 +278,119 @@ def test_cli_weights_impact_on_outcome_method(self) -> None:
             cli_none = BalanceCLI(args_none)
             self.assertIsNone(cli_none.weights_impact_on_outcome_method())
 
+    def test_process_batch_returns_failure_payload_for_empty_sample(self) -> None:
+        with tempfile.TemporaryDirectory() as temp_dir:
+            input_file = os.path.join(temp_dir, "input.csv")
+            output_file = os.path.join(temp_dir, "output.csv")
+            parser = make_parser()
+            args = parser.parse_args(
+                [
+                    "--input_file",
+                    input_file,
+                    "--output_file",
+                    output_file,
+                    "--sample_column",
+                    "is_respondent",
+                    "--covariate_columns",
+                    "x",
+                ]
+            )
+            cli = BalanceCLI(args)
+
+            batch_df = pd.DataFrame(
+                {
+                    "is_respondent": [0, 0],
+                    "id": [1, 2],
+                    "weight": [1.0, 1.0],
+                    "x": [1.0, 2.0],
+                }
+            )
+            result = cli.process_batch(batch_df)
+
+            self.assertTrue(result["adjusted"].empty)
+            self.assertEqual(
+                result["diagnostics"].to_dict("records"),
+                [
+                    {
+                        "metric": "adjustment_failure",
+                        "var": None,
+                        "val": 1,
+                    },
+                    {
+                        "metric": "adjustment_failure_reason",
+                        "var": None,
+                        "val": "No input data",
+                    },
+                ],
+            )
+
+    def test_load_and_check_input_reads_file_and_columns(self) -> None:
+        with tempfile.TemporaryDirectory() as temp_dir:
+            input_file = os.path.join(temp_dir, "input.csv")
+            output_file = os.path.join(temp_dir, "output.csv")
+            parser = make_parser()
+            args = parser.parse_args(
+                [
+                    "--input_file",
+                    input_file,
+                    "--output_file",
+                    output_file,
+                    "--sample_column",
+                    "is_respondent",
+                    "--covariate_columns",
+                    "x",
+                    "--keep_row_column",
+                    "keep",
+                ]
+            )
+            cli = BalanceCLI(args)
+
+            input_df = pd.DataFrame(
+                {
+                    "is_respondent": [1, 0],
+                    "id": [1, 2],
+                    "weight": [1.0, 1.0],
+                    "x": [1.0, 2.0],
+                    "keep": [1, 0],
+                }
+            )
+            input_df.to_csv(input_file, index=False)
+
+            loaded = cli.load_and_check_input()
+            pd.testing.assert_frame_equal(loaded, input_df)
+
+    def test_write_outputs_skips_diagnostics_when_no_output_path(self) -> None:
+        with tempfile.TemporaryDirectory() as temp_dir:
+            input_file = os.path.join(temp_dir, "input.csv")
+            output_file = os.path.join(temp_dir, "output.csv")
+            parser = make_parser()
+            args = parser.parse_args(
+                [
+                    "--input_file",
+                    input_file,
+                    "--output_file",
+                    output_file,
+                    "--sample_column",
+                    "is_respondent",
+                    "--covariate_columns",
+                    "x",
+                ]
+            )
+            cli = BalanceCLI(args)
+
+            output_df = pd.DataFrame({"id": [1], "weight": [1.25]})
+            diagnostics_df = pd.DataFrame(
+                {"metric": ["adjustment_failure"], "var": [None], "val": [0]}
+            )
+
+            cli.write_outputs(output_df, diagnostics_df)
+
+            pd.testing.assert_frame_equal(
+                pd.read_csv(output_file, sep=","),
+                output_df,
+            )
+            self.assertIsNone(cli.args.diagnostics_output_file)
+
     def test_cli_help(self) -> None:
         """Test that CLI help command executes without errors."""
         parser = make_parser()