Adds tests

Author: arielf212

tests/test_type_conversion.py

@@ -1,6 +1,6 @@
 from enum import Enum
 from pathlib import Path
-from typing import Any, List, Optional, Tuple
+from typing import Any, List, Optional, Tuple, Union
 
 import click
 import pytest
@@ -50,6 +50,31 @@ def opt(user: str | None = None):
     assert result.exit_code == 0
     assert "User: Camila" in result.output
 
+@pytest.mark.parametrize(
+    ("value", "expected"),
+    [
+        ("0", "ROOTED!"),
+        ("12", "ID: 12"),
+        ("name", "USER: name")
+    ],
+)
+def test_union(value, expected):
+    app = typer.Typer()
+    
+    @app.command()
+    def opt(id_or_name: Union[int, str]):
+        if isinstance(id_or_name, int):
+            if id_or_name == 0:
+                print("ROOTED!")
+            else:
+                print(f"ID: {id_or_name}")
+        else:
+            print(f"USER: {id_or_name}")
+    
+    result = runner.invoke(app, [value])
+    assert result.exit_code == 0
+    assert expected  in result.output
+        
 
 def test_optional_tuple():
     app = typer.Typer()