diff --git a/python/grass/script/core.py b/python/grass/script/core.py
index afac1b15ac1..59d96577a4d 100644
--- a/python/grass/script/core.py
+++ b/python/grass/script/core.py
@@ -128,7 +128,7 @@ def _make_unicode(val, enc):
             return decode(val, encoding=enc)
 
 
-def get_commands():
+def get_commands(*, env=None):
     """Create list of available GRASS commands to use when parsing
     string from the command line
 
@@ -141,7 +141,17 @@ def get_commands():
     ['d.barscale', 'd.colorlist', 'd.colortable', 'd.correlate', 'd.erase']
 
     """
-    gisbase = os.environ["GISBASE"]
+    if not env:
+        env = os.environ
+    gisbase = env.get("GISBASE")
+
+    # Lazy-importing to avoid circular dependencies.
+    # pylint: disable=import-outside-toplevel
+    if not gisbase:
+        from grass.script.setup import get_install_path
+
+        gisbase = get_install_path()
+
     cmd = list()
     scripts = {".py": list()} if sys.platform == "win32" else {}
 
diff --git a/python/grass/script/tests/conftest.py b/python/grass/script/tests/conftest.py
new file mode 100644
index 00000000000..ce666fbdeef
--- /dev/null
+++ b/python/grass/script/tests/conftest.py
@@ -0,0 +1,20 @@
+"""Fixtures for grass.script"""
+
+import pytest
+
+
+@pytest.fixture
+def mock_no_session(monkeypatch):
+    """Set the environment variables as if there would be no background session.
+
+    Use with usefixtures (not as a paramter) to avoid warnings about an unused
+    parameter::
+
+        @pytest.mark.usefixtures("mock_no_session")
+        def test_session_handling():
+            pass
+
+    There may or may not be a session in the background (we don't check either way).
+    """
+    monkeypatch.delenv("GISRC", raising=False)
+    monkeypatch.delenv("GISBASE", raising=False)
diff --git a/python/grass/script/tests/grass_script_core_get_commands.py b/python/grass/script/tests/grass_script_core_get_commands.py
new file mode 100644
index 00000000000..afb2f6c62dc
--- /dev/null
+++ b/python/grass/script/tests/grass_script_core_get_commands.py
@@ -0,0 +1,47 @@
+"""Test grass.script.core.get_commands function"""
+
+import sys
+
+import pytest
+
+import grass.script as gs
+
+
+def common_test_code(executables_set, scripts_dict):
+    """Assert results
+
+    Assuming we should always have some executables on path for this to pass a test.
+    """
+    assert len(executables_set)
+    assert "g.region" in executables_set
+    if sys.platform == "win32":
+        assert len(scripts_dict.items())
+        # Just in case this is not a standard dictionary object.
+        assert len(scripts_dict.keys()) == len(scripts_dict.items())
+        assert "r.shade" in scripts_dict["py"]
+    else:
+        assert "r.shade" in executables_set
+
+
+def test_no_explicit_session():
+    """Test without explicit session setup here"""
+    executables_set, scripts_dict = gs.get_commands()
+    common_test_code(executables_set, scripts_dict)
+
+
+@pytest.mark.usefixtures("mock_no_session")
+def test_no_session_mocked():
+    """Test with mocked no session"""
+    executables_set, scripts_dict = gs.get_commands()
+    common_test_code(executables_set, scripts_dict)
+
+
+@pytest.mark.usefixtures("mock_no_session")
+def test_in_session(tmp_path):
+    """Test with mocked no session"""
+    # TODO: Use env=os.environ.copy()
+    project = tmp_path / "project"
+    gs.create_project(project)
+    with gs.setup.init(project) as session:
+        executables_set, scripts_dict = gs.get_commands(env=session.env)
+    common_test_code(executables_set, scripts_dict)