test_install: add test_pip_args_with_constraint_relative_path

tests/test_install.py

@@ -264,6 +264,27 @@ def test_pip_args_with_windows_path(pipx_temp_env, capsys):
     assert r"D:\\TEST\\DIR" in captured.err
 
 
+@pytest.mark.parametrize("constraint_flag", ["-c ", "--constraint ", "--constraint="])
+def test_pip_args_with_constraint_relative_path(constraint_flag, pipx_temp_env, tmp_path, caplog):
+    constraint_file_name = "constraint.txt"
+    pycowsay_version = "0.0.0.1"
+
+    os.chdir(tmp_path)
+    current_directory = Path(".").expanduser().resolve()
+
+    temp_file = current_directory / constraint_file_name
+    temp_file.touch()
+    temp_file.write_text(f"pycowsay=={pycowsay_version}")
+
+    assert run_pipx_cli(["install", f"--pip-args='{constraint_flag}{constraint_file_name}'", "pycowsay"]) == 0
+
+    assert f"{constraint_flag}{temp_file}" in caplog.text
+
+    subprocess_pycowsay_version = subprocess.run(["pycowsay", "--version"], capture_output=True, text=True, check=False)
+    subprocess_pycowsay_version_output = subprocess_pycowsay_version.stdout.strip()
+    assert subprocess_pycowsay_version_output == pycowsay_version
+
+
 def test_install_suffix(pipx_temp_env, capsys):
     name = "pbr"