diff --git a/src/itzi/itzi.py b/src/itzi/itzi.py
index 6a2080b..51979ef 100644
--- a/src/itzi/itzi.py
+++ b/src/itzi/itzi.py
@@ -33,7 +33,7 @@
 from datetime import datetime, timedelta
 from importlib.metadata import version
 from multiprocessing import Process
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Callable
 
 import numpy as np
 
@@ -41,7 +41,7 @@
 import itzi.itzi_error as itzi_error
 import itzi.messenger as msgr
 from itzi.const import VerbosityLevel
-from itzi import parser
+from itzi.parser import build_parser
 from itzi.profiler import profile_context
 from itzi.simulation_builder import SimulationBuilder
 from itzi.grass_session import GrassSessionManager
@@ -52,16 +52,17 @@
     from itzi.simulation import Simulation
 
 
-def main():
-    # default functions for subparsers
-    parser.run_parser.set_defaults(func=itzi_run)
-    parser.version_parser.set_defaults(func=itzi_version)
-    # get parsed arguments
-    args = parser.arg_parser.parse_args()
-    try:
-        args.func(args)
-    except AttributeError:
-        parser.arg_parser.print_usage()
+def main(argv=None):
+    """argv: alternative CLI arguments, used for testing (default to sys.argv)"""
+    args = build_parser().parse_args(argv)
+
+    command_mapper: dict[str, Callable] = {
+        "run": itzi_run,
+        "version": itzi_version,
+    }
+
+    # args.command is the name of the subcommand
+    command_mapper[args.command](args)
 
 
 class SimulationRunner:
diff --git a/src/itzi/parser.py b/src/itzi/parser.py
index f24c1e8..cb63aa8 100644
--- a/src/itzi/parser.py
+++ b/src/itzi/parser.py
@@ -5,21 +5,24 @@
 
 DESCR = "A dynamic, fully distributed hydraulic and hydrologic model."
 
-arg_parser = argparse.ArgumentParser(description=DESCR)
-subparsers = arg_parser.add_subparsers()
-
-# run a simulation
-run_parser = subparsers.add_parser("run", help="run a simulation")
-run_parser.add_argument(
-    "config_file",
-    nargs="+",
-    help=("an Itzï configuration file (if several given, run in batch mode)"),
-)
-run_parser.add_argument("-o", action="store_true", help="overwrite files if exist")
-verbosity_parser = run_parser.add_mutually_exclusive_group()
-verbosity_parser.add_argument("-v", action="count", help="increase verbosity")
-verbosity_parser.add_argument("-q", action="count", help="decrease verbosity")
-
-
-# display version
-version_parser = subparsers.add_parser("version", help="display software version number")
+
+def build_parser() -> argparse.ArgumentParser:
+    arg_parser = argparse.ArgumentParser(description=DESCR)
+    subparsers = arg_parser.add_subparsers(dest="command", required=True)
+
+    # run a simulation
+    run_parser = subparsers.add_parser("run", help="run a simulation")
+    run_parser.add_argument(
+        "config_file",
+        nargs="+",
+        help=("an Itzï configuration file (if several given, run in batch mode)"),
+    )
+    run_parser.add_argument("-o", action="store_true", help="overwrite files if exist")
+    verbosity_parser = run_parser.add_mutually_exclusive_group()
+    verbosity_parser.add_argument("-v", action="count", help="increase verbosity")
+    verbosity_parser.add_argument("-q", action="count", help="decrease verbosity")
+
+    # display version
+    subparsers.add_parser("version", help="display software version number")
+
+    return arg_parser
diff --git a/tests/cli/test_cli.py b/tests/cli/test_cli.py
new file mode 100644
index 0000000..c421bb0
--- /dev/null
+++ b/tests/cli/test_cli.py
@@ -0,0 +1,52 @@
+"""Test the CLI"""
+
+import argparse
+import os
+
+import pytest
+
+from itzi.const import VerbosityLevel
+from itzi.itzi import main, itzi_run
+from itzi.parser import build_parser
+
+
+def test_run_parser_accepts_multiple_config_files():
+    args = build_parser().parse_args(["run", "a.ini", "b.ini", "-o", "-vv"])
+    assert args.config_file == ["a.ini", "b.ini"]
+    assert args.o is True
+    assert args.v == 2
+    assert args.q is None
+
+
+def test_run_parser_rejects_v_and_q_together():
+    with pytest.raises(SystemExit):
+        build_parser().parse_args(["run", "a.ini", "-v", "-q"])
+
+
+def test_prints_version(monkeypatch, capsys):
+    monkeypatch.setattr("itzi.itzi.version", lambda _: "22.2")
+    assert main(["version"]) is None
+    assert capsys.readouterr().out.strip() == "22.2"
+
+
+def test_itzi_run_sets_env_and_dispatches(monkeypatch):
+    calls = []
+    messages = []
+
+    monkeypatch.setattr("itzi.itzi.itzi_run_one", calls.append)
+    monkeypatch.setattr("itzi.itzi.msgr.message", messages.append)
+
+    args = argparse.Namespace(
+        config_file=["a.ini", "b.ini"],
+        o=True,
+        v=1,
+        q=None,
+    )
+
+    itzi_run(args)
+
+    assert calls == ["a.ini", "b.ini"]
+    assert os.environ["GRASS_OVERWRITE"] == "1"
+    assert os.environ["ITZI_VERBOSE"] == str(VerbosityLevel.VERBOSE)
+    assert os.environ["GRASS_VERBOSE"] == "2"
+    assert any("Simulation(s) complete" in m for m in messages)
diff --git a/tests/core/test_configreader.py b/tests/cli/test_configreader.py
similarity index 100%
rename from tests/core/test_configreader.py
rename to tests/cli/test_configreader.py