add fixture to capture output in tests less fragile

Now we always remove previous output before capturing.

pkgs/clan-cli/tests/conftest.py

@@ -15,6 +15,7 @@ pytest_plugins = [
     "ports",
     "host_group",
     "fixtures_flakes",
+    "stdout",
 ]
 
 

pkgs/clan-cli/tests/stdout.py

@@ -0,0 +1,23 @@
+from typing import Any
+
+import pytest
+from pytest import CaptureFixture
+
+
+class CaptureOutput:
+    def __init__(self, capsys: CaptureFixture) -> None:
+        self.capsys = capsys
+
+    def __enter__(self) -> "CaptureOutput":
+        self.capsys.readouterr()
+        return self
+
+    def __exit__(self, exc_type: Any, exc_value: Any, exc_traceback: Any) -> bool:
+        res = self.capsys.readouterr()
+        self.out = res.out
+        self.err = res.err
+
+
+@pytest.fixture
+def capture_output(capsys: CaptureFixture) -> CaptureOutput:
+    return CaptureOutput(capsys)

pkgs/clan-cli/tests/test_cli.py

@@ -1,9 +1,9 @@
 import pytest
 from helpers import cli
+from stdout import CaptureOutput
 
 
-def test_help(capsys: pytest.CaptureFixture) -> None:
-    with pytest.raises(SystemExit):
+def test_help(capture_output: CaptureOutput) -> None:
+    with capture_output as output, pytest.raises(SystemExit):
         cli.run(["--help"])
-    captured = capsys.readouterr()
-    assert captured.out.startswith("usage:")
+    assert output.out.startswith("usage:")

pkgs/clan-cli/tests/test_create_flake.py

@@ -5,14 +5,15 @@ from pathlib import Path
 import pytest
 from fixtures_flakes import substitute
 from helpers import cli
+from stdout import CaptureOutput
 
 
 @pytest.mark.impure
 def test_create_flake(
     monkeypatch: pytest.MonkeyPatch,
-    capsys: pytest.CaptureFixture,
     temporary_home: Path,
     clan_core: Path,
+    capture_output: CaptureOutput,
 ) -> None:
     flake_dir = temporary_home / "test-flake"
 
@@ -29,7 +30,6 @@ def test_create_flake(
 
     monkeypatch.chdir(flake_dir)
     cli.run(["machines", "create", "machine1"])
-    capsys.readouterr()  # flush cache
 
     # create a hardware-configuration.nix that doesn't throw an eval error
 
@@ -39,8 +39,9 @@ def test_create_flake(
         ) as hw_config_nix:
             hw_config_nix.write("{}")
 
+    with capture_output as output:
         cli.run(["machines", "list"])
-    assert "machine1" in capsys.readouterr().out
+    assert "machine1" in output.out
     flake_show = subprocess.run(
         ["nix", "flake", "show", "--json"],
         check=True,
@@ -57,9 +58,9 @@ def test_create_flake(
 @pytest.mark.impure
 def test_ui_template(
     monkeypatch: pytest.MonkeyPatch,
-    capsys: pytest.CaptureFixture,
     temporary_home: Path,
     clan_core: Path,
+    capture_output: CaptureOutput,
 ) -> None:
     flake_dir = temporary_home / "test-flake"
     url = f"{clan_core}#minimal"
@@ -73,10 +74,10 @@ def test_ui_template(
 
     monkeypatch.chdir(flake_dir)
     cli.run(["machines", "create", "machine1"])
-    capsys.readouterr()  # flush cache
 
+    with capture_output as output:
         cli.run(["machines", "list"])
-    assert "machine1" in capsys.readouterr().out
+    assert "machine1" in output.out
     flake_show = subprocess.run(
         ["nix", "flake", "show", "--json"],
         check=True,

pkgs/clan-cli/tests/test_history_cli.py

@@ -4,7 +4,7 @@ from typing import TYPE_CHECKING
 import pytest
 from fixtures_flakes import FlakeForTest
 from helpers import cli
-from pytest import CaptureFixture
+from stdout import CaptureOutput
 
 from clan_cli.dirs import user_history_file
 from clan_cli.history.add import HistoryEntry
@@ -32,15 +32,15 @@ def test_history_add(
 
 @pytest.mark.impure
 def test_history_list(
-    capsys: CaptureFixture,
+    capture_output: CaptureOutput,
     test_flake_with_core: FlakeForTest,
 ) -> None:
-    capsys.readouterr()
+    with capture_output as output:
         cli.run(["history", "list"])
-    assert str(test_flake_with_core.path) not in capsys.readouterr().out
+    assert str(test_flake_with_core.path) not in output.out
 
     cli.run(["history", "add", f"clan://{test_flake_with_core.path}#vm1"])
 
-    capsys.readouterr()
+    with capture_output as output:
         cli.run(["history", "list"])
-    assert str(test_flake_with_core.path) in capsys.readouterr().out
+    assert str(test_flake_with_core.path) in output.out

pkgs/clan-cli/tests/test_vms_cli.py

@@ -3,6 +3,7 @@ from pathlib import Path
 from typing import TYPE_CHECKING
 
 import pytest
+from stdout import CaptureOutput
 
 from tests.fixtures_flakes import FlakeForTest, generate_flake
 from tests.helpers import cli
@@ -18,11 +19,11 @@ no_kvm = not os.path.exists("/dev/kvm")
 
 @pytest.mark.impure
 def test_inspect(
-    test_flake_with_core: FlakeForTest, capsys: pytest.CaptureFixture
+    test_flake_with_core: FlakeForTest, capture_output: CaptureOutput
 ) -> None:
+    with capture_output as output:
         cli.run(["vms", "inspect", "--flake", str(test_flake_with_core.path), "vm1"])
-    out = capsys.readouterr()  # empty the buffer
-    assert "Cores" in out.out
+    assert "Cores" in output.out
 
 
 @pytest.mark.skipif(no_kvm, reason="Requires KVM")