quite a bit of development around get rates input handling

tests/tests_cli/test_xe_get_rates.py

@@ -0,0 +1,37 @@
+from click.testing import CliRunner
+
+from xexe.cli import get_rates
+
+
+def test_get_rates_reads_input_correctly():
+
+    runner = CliRunner()
+
+    run_result = runner.invoke(
+        get_rates,
+        [
+            "--start-date",
+            "2024-01-01",
+            "--end-date",
+            "2024-01-02",
+            "--currencies",
+            "USD,GBP",
+            "--output",
+            "test_output.csv",
+            "--dry-run",
+        ],
+    )
+
+    assert run_result.exit_code == 0
+
+
+def test_get_rates_works_with_defaults():
+    runner = CliRunner()
+    result = runner.invoke(get_rates, ["--output", "test_output.csv"])
+    assert result.exit_code == 0
+
+
+def test_get_rates_breaks_without_output():
+    runner = CliRunner()
+    result = runner.invoke(get_rates)
+    assert result.exit_code == 2