diff --git a/changelog.md b/changelog.md
index c7e89e28..585fb5bc 100644
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,11 @@
+Upcoming (TBD)
+==============
+
+Internal
+---------
+* Improve test coverage for DSN variable expansion.
+
+
 1.76.0 (2026/06/20)
 ==============
 
diff --git a/test/pytests/test_cli_runner.py b/test/pytests/test_cli_runner.py
index 3e491e91..f7a65b5e 100644
--- a/test/pytests/test_cli_runner.py
+++ b/test/pytests/test_cli_runner.py
@@ -74,6 +74,31 @@ def run_with_client(
     return client
 
 
+def test_expand_dsn_alias_env_var_returns_none() -> None:
+    assert cli_runner.expand_dsn_alias_env_var(None, 'prod') is None
+
+
+def test_split_dsn_netloc_handles_user_without_password() -> None:
+    assert cli_runner.split_dsn_netloc('user@host:3306') == ('user', None, 'host', '3306')
+
+
+def test_split_dsn_netloc_handles_empty_host() -> None:
+    assert cli_runner.split_dsn_netloc('user:pass@') == ('user', 'pass', None, None)
+
+
+def test_split_dsn_netloc_handles_bracketed_ipv6_host() -> None:
+    assert cli_runner.split_dsn_netloc('user:pass@[::1]:3306') == ('user', 'pass', '::1', '3306')
+
+
+def test_expand_dsn_alias_env_vars_rejects_non_integer_port(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setenv('MYCLI_TEST_DSN_PORT', 'not-an-int')
+
+    with pytest.raises(cli_runner.DsnAliasEnvVarError) as excinfo:
+        cli_runner.expand_dsn_alias_env_vars('mysql://user:pass@host:${MYCLI_TEST_DSN_PORT}/db', 'prod')
+
+    assert str(excinfo.value) == 'Port in DSN alias prod must be an integer.'
+
+
 def test_run_from_cli_args_checkup_exits_zero(monkeypatch: pytest.MonkeyPatch) -> None:
     cli_args = make_cli_args()
     cli_args.checkup = True