diff --git a/test/fixtures/reverse.csv b/test/fixtures/reverse.csv
new file mode 100644
index 0000000..93d2e2b
--- /dev/null
+++ b/test/fixtures/reverse.csv
@@ -0,0 +1 @@
+1,51.9526622,7.6324709
\ No newline at end of file
diff --git a/test/test_cli_args.py b/test/test_cli_args.py
index 0f918ab..c75b776 100644
--- a/test/test_cli_args.py
+++ b/test/test_cli_args.py
@@ -6,7 +6,7 @@
 @pytest.fixture(autouse=True)
 def around():
     yield
-    pathlib.Path("test/fixtures/output.txt").unlink(True)
+    pathlib.Path("test/fixtures/output.csv").unlink(True)
 
 def assert_parse_args_error(args, message, capfd):
     with pytest.raises(SystemExit):
@@ -27,7 +27,7 @@ def test_invalid_api_key(capfd):
         [
             "--api-key", "invalid",
             "--input", "test/fixtures/input.txt",
-            "--output", "test/fixtures/output.txt",
+            "--output", "test/fixtures/output.csv",
             "--forward"
         ],
         'invalid API key',
@@ -51,7 +51,7 @@ def test_requires_forward_or_reverse(capfd):
         [
             "--api-key", "oc_gc_12345678901234567890123456789012",
             "--input", "test/fixtures/input.txt",
-            "--output", "test/fixtures/output.txt",
+            "--output", "test/fixtures/output.csv",
         ],
         'one of the arguments --forward --reverse is required',
         capfd
@@ -62,7 +62,7 @@ def test_argument_range(capfd):
         [
             "--api-key", "oc_gc_12345678901234567890123456789012",
             "--input", "test/fixtures/input.txt",
-            "--output", "test/fixtures/output.txt",
+            "--output", "test/fixtures/output.csv",
             "--forward",
             "--workers", "200"
         ],
@@ -74,7 +74,7 @@ def test_full_argument_list():
     args = parse_args([
         "--api-key", "oc_gc_12345678901234567890123456789012",
         "--input", "test/fixtures/input.txt",
-        "--output", "test/fixtures/output.txt",
+        "--output", "test/fixtures/output.csv",
         "--reverse",
         "--has-header",
         "--input-columns", "1,2",
@@ -92,7 +92,7 @@ def test_full_argument_list():
 
     assert args.api_key == "oc_gc_12345678901234567890123456789012"
     assert args.input.name == "test/fixtures/input.txt"
-    assert args.output.name == "test/fixtures/output.txt"
+    assert args.output.name == "test/fixtures/output.csv"
     assert args.reverse is True
     assert args.forward is False
     assert args.has_headers is True
@@ -112,7 +112,7 @@ def test_defaults():
     args = parse_args([
         "--api-key", "12345678901234567890123456789012",
         "--input", "test/fixtures/input.txt",
-        "--output", "test/fixtures/output.txt",
+        "--output", "test/fixtures/output.csv",
         "--reverse"
     ])
 
diff --git a/test/test_cli_run.py b/test/test_cli_run.py
index b2039ca..85f67f4 100644
--- a/test/test_cli_run.py
+++ b/test/test_cli_run.py
@@ -8,21 +8,44 @@
 @pytest.fixture(autouse=True)
 def around():
     yield
-    pathlib.Path("test/fixtures/output.txt").unlink(True)
+    pathlib.Path("test/fixtures/output.csv").unlink(True)
 
-@pytest.mark.asyncio
-def test_main():
+def assert_output(path, length, lines):
+    assert pathlib.Path(path).exists()
+
+    with open(path, "r") as f:
+        actual = f.readlines()
+        assert len(actual) == length
+
+        for i, expected in enumerate(lines):
+            assert actual[i].strip() == expected
+
+def test_forward():
     main([
         "--api-key", "6d0e711d72d74daeb2b0bfd2a5cdfdba",
         "--input", "test/fixtures/forward.csv",
-        "--output", "test/fixtures/output.txt",
+        "--output", "test/fixtures/output.csv",
         "--forward",
         "--input-columns", "2,3,4",
     ])
 
-    assert pathlib.Path("test/fixtures/output.txt").exists()
+    assert_output(
+        path="test/fixtures/output.csv",
+        length=3,
+        lines=['1,51.9526622,7.6324709,social_facility,Germany,,Münster,48153,Friedrich-Ebert-Straße,7,9,"Chance e.V., Friedrich-Ebert-Straße 7, 48153 Münster, Germany"']
+    )
+
+def test_reverse():
+    main([
+        "--api-key", "6d0e711d72d74daeb2b0bfd2a5cdfdba",
+        "--input", "test/fixtures/reverse.csv",
+        "--output", "test/fixtures/output.csv",
+        "--reverse",
+        "--add-columns", "city,postcode"
+    ])
 
-    with open("test/fixtures/output.txt", "r") as f:
-        lines = f.readlines()
-        assert len(lines) == 3
-        assert lines[0].strip() == '1,51.9526622,7.6324709,social_facility,Germany,,Münster,48153,Friedrich-Ebert-Straße,7,9,"Chance e.V., Friedrich-Ebert-Straße 7, 48153 Münster, Germany"'
+    assert_output(
+        path="test/fixtures/output.csv",
+        length=1,
+        lines=['1,51.9526622,7.6324709,Münster,48153']
+    )