--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test_tables_ops.py	Mon Dec 08 15:03:06 2025 +0000
@@ -0,0 +1,105 @@
+import unittest
+import subprocess
+import os
+import csv
+
+
+class TestTableOps(unittest.TestCase):
+    TEST_DATA_DIR = "test-data"
+
+    def _run_command(self, command, input_data=None):
+        process = subprocess.Popen(
+            command,
+            stdin=subprocess.PIPE if input_data else None,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            text=True,  # Important for handling text I/O
+        )
+        stdout, stderr = process.communicate(input_data)
+        return process.returncode, stdout, stderr
+
+    def _compare_tsv(self, expected_file, actual_output):
+        with open(
+            os.path.join(self.TEST_DATA_DIR, expected_file), "r", encoding="utf-8"
+        ) as f:
+            expected_lines = list(csv.reader(f, delimiter="\t"))
+        actual_lines = list(csv.reader(actual_output.splitlines(), delimiter="\t"))
+        self.assertEqual(expected_lines, actual_lines)
+
+    def test_table_union_union(self):
+        returncode, stdout, stderr = self._run_command(
+            [
+                "table-union",
+                os.path.join(self.TEST_DATA_DIR, "dingbat.tsv"),
+                os.path.join(self.TEST_DATA_DIR, "loki.tsv"),
+            ]
+        )
+        self.assertEqual(returncode, 0)
+        self._compare_tsv("combined.tsv", stdout)
+        self.assertEqual(stderr, "")
+
+    def test_table_union_join(self):
+        returncode, stdout, stderr = self._run_command(
+            [
+                "table-union",
+                "--no-union",
+                os.path.join(self.TEST_DATA_DIR, "users.tsv"),
+                os.path.join(self.TEST_DATA_DIR, "orders.tsv"),
+            ]
+        )
+        self.assertEqual(returncode, 0)
+        self._compare_tsv("merged_expected.tsv", stdout)
+        self.assertEqual(stderr, "")
+
+    def test_table_summarize(self):
+        returncode, stdout, stderr = self._run_command(
+            ["table-summarize", os.path.join(self.TEST_DATA_DIR, "data_summarize.tsv")]
+        )
+        self.assertEqual(returncode, 0)
+
+        expected_summary = """Summary:
+Category:
+\t - A: 3 of 6
+\t - B: 2 of 6
+\t - C: 1 of 6
+Value:
+\t - 10: 1 of 6
+\t - 12: 1 of 6
+\t - 15: 1 of 6
+\t - 20: 1 of 6
+\t - 25: 1 of 6
+\t - 30: 1 of 6
+"""
+        self.assertEqual(stdout.strip(), expected_summary.strip())
+        self.assertEqual(stderr, "")
+
+    def test_table_sort(self):
+        returncode, stdout, stderr = self._run_command(
+            [
+                "table-sort",
+                "-k",
+                "Age",
+                "-k",
+                "Name",
+                os.path.join(self.TEST_DATA_DIR, "data_sort.tsv"),
+            ]
+        )
+        self.assertEqual(returncode, 0)
+        self._compare_tsv("sorted_data_expected.tsv", stdout)
+        self.assertEqual(stderr, "")
+
+    def test_table_sort_pipe(self):
+        with open(
+            os.path.join(self.TEST_DATA_DIR, "data_sort.tsv"), "r", encoding="utf-8"
+        ) as infile:
+            input_data = infile.read()
+        returncode, stdout, stderr = self._run_command(
+            ["table-sort", "-k", "Age", "-k", "Name"], input_data
+        )
+        self.assertEqual(returncode, 0)
+        self._compare_tsv("sorted_data_expected.tsv", stdout)
+        self.assertEqual(stderr, "")
+
+
+if __name__ == "__main__":
+    unittest.main()