diff --git a/dangerzone/errors.py b/dangerzone/errors.py
index 63dc4e7..dbbcb4b 100644
--- a/dangerzone/errors.py
+++ b/dangerzone/errors.py
@@ -95,7 +95,7 @@ class SuffixNotApplicableException(DocumentFilenameException):
 
 
 def handle_document_errors(func: F) -> F:
-    """Log document-related errors and exit gracefully."""
+    """Decorator to log document-related errors and exit gracefully."""
 
     @functools.wraps(func)
     def wrapper(*args, **kwargs):  # type: ignore
diff --git a/dangerzone/isolation_provider/base.py b/dangerzone/isolation_provider/base.py
index 5b05789..308a05e 100644
--- a/dangerzone/isolation_provider/base.py
+++ b/dangerzone/isolation_provider/base.py
@@ -55,7 +55,7 @@ class IsolationProvider(ABC):
     """
 
     def __init__(self) -> None:
-        if getattr(sys, "dangerzone_dev", False) == True:
+        if getattr(sys, "dangerzone_dev", False) is True:
             self.proc_stderr = subprocess.PIPE
         else:
             self.proc_stderr = subprocess.DEVNULL
diff --git a/dangerzone/isolation_provider/qubes.py b/dangerzone/isolation_provider/qubes.py
index 5a2395d..aa59006 100644
--- a/dangerzone/isolation_provider/qubes.py
+++ b/dangerzone/isolation_provider/qubes.py
@@ -51,7 +51,7 @@ class Qubes(IsolationProvider):
         return 1
 
     def start_doc_to_pixels_proc(self, document: Document) -> subprocess.Popen:
-        dev_mode = getattr(sys, "dangerzone_dev", False) == True
+        dev_mode = getattr(sys, "dangerzone_dev", False) is True
         if dev_mode:
             # Use dz.ConvertDev RPC call instead, if we are in development mode.
             # Basically, the change is that we also transfer the necessary Python
diff --git a/tests/gui/test_main_window.py b/tests/gui/test_main_window.py
index b649dc7..23e0da9 100644
--- a/tests/gui/test_main_window.py
+++ b/tests/gui/test_main_window.py
@@ -58,7 +58,7 @@ def test_default_menu(
 
     toggle_updates_action.trigger()
     assert not toggle_updates_action.isChecked()
-    assert updater.dangerzone.settings.get("updater_check") == False
+    assert updater.dangerzone.settings.get("updater_check") is False
 
 
 def test_no_update(
@@ -365,13 +365,13 @@ def test_change_document_button(
         file_dialog_mock.accept()
 
     # Then two dialogs should have been open
-    assert file_dialog_mock.exec.call_count is 2
-    assert file_dialog_mock.selectedFiles.call_count is 2
+    assert file_dialog_mock.exec.call_count == 2
+    assert file_dialog_mock.selectedFiles.call_count == 2
 
     # Then the final document should be only the second one
     docs = [
         doc.input_filename
         for doc in content_widget.dangerzone.get_unconverted_documents()
     ]
-    assert len(docs) is 1
+    assert len(docs) == 1
     assert docs[0] == str(tmp_sample_doc)
diff --git a/tests/gui/test_updater.py b/tests/gui/test_updater.py
index e6f76c2..8572ad7 100644
--- a/tests/gui/test_updater.py
+++ b/tests/gui/test_updater.py
@@ -114,7 +114,7 @@ def test_linux_no_check(updater: UpdaterThread, monkeypatch: MonkeyPatch) -> Non
     # XXX: Simulate Dangerzone installed via package manager.
     monkeypatch.delattr(sys, "dangerzone_dev")
 
-    assert updater.should_check_for_updates() == False
+    assert updater.should_check_for_updates() is False
     assert updater.dangerzone.settings.get_updater_settings() == expected_settings
 
 
@@ -129,7 +129,7 @@ def test_user_prompts(
     expected_settings = default_updater_settings()
     expected_settings["updater_check"] = None
     expected_settings["updater_last_check"] = 0
-    assert updater.should_check_for_updates() == False
+    assert updater.should_check_for_updates() is False
     assert updater.dangerzone.settings.get_updater_settings() == expected_settings
 
     # Second run
@@ -143,14 +143,14 @@ def test_user_prompts(
     # Check disabling update checks.
     prompt_mock().launch.return_value = False  # type: ignore [attr-defined]
     expected_settings["updater_check"] = False
-    assert updater.should_check_for_updates() == False
+    assert updater.should_check_for_updates() is False
     assert updater.dangerzone.settings.get_updater_settings() == expected_settings
 
     # Reset the "updater_check" field and check enabling update checks.
     updater.dangerzone.settings.set("updater_check", None)
     prompt_mock().launch.return_value = True  # type: ignore [attr-defined]
     expected_settings["updater_check"] = True
-    assert updater.should_check_for_updates() == True
+    assert updater.should_check_for_updates() is True
     assert updater.dangerzone.settings.get_updater_settings() == expected_settings
 
     # Third run
@@ -232,7 +232,7 @@ def test_update_checks_cooldown(updater: UpdaterThread, mocker: MockerFixture) -
     timestamp_mock.return_value = curtime
 
     report = updater.check_for_updates()
-    assert cooldown_spy.spy_return == False
+    assert cooldown_spy.spy_return is False
     assert updater.dangerzone.settings.get("updater_last_check") == curtime
     assert_report_equal(report, UpdateReport("99.9.9", "<p>changelog</p>"))
 
@@ -246,7 +246,7 @@ def test_update_checks_cooldown(updater: UpdaterThread, mocker: MockerFixture) -
     updater.dangerzone.settings.set("updater_latest_changelog", None)
 
     report = updater.check_for_updates()
-    assert cooldown_spy.spy_return == True
+    assert cooldown_spy.spy_return is True
     assert updater.dangerzone.settings.get("updater_last_check") == curtime - 1
     assert_report_equal(report, UpdateReport())
 
@@ -257,7 +257,7 @@ def test_update_checks_cooldown(updater: UpdaterThread, mocker: MockerFixture) -
     requests_mock.side_effect = None  # type: ignore [attr-defined]
 
     report = updater.check_for_updates()
-    assert cooldown_spy.spy_return == False
+    assert cooldown_spy.spy_return is False
     assert updater.dangerzone.settings.get("updater_last_check") == curtime
     assert_report_equal(report, UpdateReport("99.9.9", "<p>changelog</p>"))
 
@@ -272,7 +272,7 @@ def test_update_checks_cooldown(updater: UpdaterThread, mocker: MockerFixture) -
     requests_mock.side_effect = Exception("failed")  # type: ignore [attr-defined]
 
     report = updater.check_for_updates()
-    assert cooldown_spy.spy_return == False
+    assert cooldown_spy.spy_return is False
     assert updater.dangerzone.settings.get("updater_last_check") == curtime
     error_msg = (
         f"Encountered an exception while checking {updater.GH_RELEASE_URL}: failed"
@@ -388,7 +388,7 @@ def test_update_check_prompt(
     QtCore.QTimer.singleShot(500, check_button_labels)
     res = qt_updater.should_check_for_updates()
 
-    assert res == True
+    assert res is True
 
     # Test 2 - Check that when the user chooses to enable update checks, we
     # store that decision in the settings.
@@ -401,8 +401,8 @@ def test_update_check_prompt(
     QtCore.QTimer.singleShot(500, click_ok)
     res = qt_updater.should_check_for_updates()
 
-    assert res == True
-    assert qt_updater.check == True
+    assert res is True
+    assert qt_updater.check is True
 
     # Test 3 - Same as the previous test, but check that clicking on cancel stores the
     # opposite decision.
@@ -415,8 +415,8 @@ def test_update_check_prompt(
     QtCore.QTimer.singleShot(500, click_cancel)
     res = qt_updater.should_check_for_updates()
 
-    assert res == False
-    assert qt_updater.check == False
+    assert res is False
+    assert qt_updater.check is False
 
     # Test 4 - Same as the previous test, but check that clicking on "X" does not store
     # any decision.
@@ -429,5 +429,5 @@ def test_update_check_prompt(
     QtCore.QTimer.singleShot(500, click_x)
     res = qt_updater.should_check_for_updates()
 
-    assert res == False
-    assert qt_updater.check == None
+    assert res is False
+    assert qt_updater.check is None
diff --git a/tests/isolation_provider/test_dummy.py b/tests/isolation_provider/test_dummy.py
index 04ccf97..9d4041b 100644
--- a/tests/isolation_provider/test_dummy.py
+++ b/tests/isolation_provider/test_dummy.py
@@ -35,11 +35,10 @@ def provider_wait() -> DummyWait:
 
 
 @pytest.mark.skipif(
-    os.environ.get("DUMMY_CONVERSION", False) == False,
+    os.environ.get("DUMMY_CONVERSION", False) is False,
     reason="can only run for dummy conversions",
 )
 class TestDummyTermination(IsolationProviderTermination):
-
     def test_failed(
         self,
         provider_wait: IsolationProvider,