tests: fix and improve installer test coverage

This change improves test scenarios for installer with dependency
groups. Previously, the usage of populated installed repositories
could lead to tests incorrectly passing as no operations were
performed. These cases now forces syncronisation and uses a clean
installed repository instance instead.

tests/installation/test_installer.py

@@ -309,6 +309,7 @@ def _configure_run_install_dev(
     package: ProjectPackage,
     installed: CustomInstalledRepository,
     with_optional_group: bool = False,
+    with_packages_installed: bool = False,
 ) -> None:
     """
     Perform common test setup for `test_run_install_*dev*()` methods.
@@ -360,9 +361,10 @@ def _configure_run_install_dev(
     repo.add_package(package_b)
     repo.add_package(package_c)
 
-    installed.add_package(package_a)
-    installed.add_package(package_b)
-    installed.add_package(package_c)
+    if with_packages_installed:
+        installed.add_package(package_a)
+        installed.add_package(package_b)
+        installed.add_package(package_c)
 
     package.add_dependency(Factory.create_dependency("A", "~1.0"))
     package.add_dependency(Factory.create_dependency("B", "~1.1"))
@@ -372,41 +374,27 @@ def _configure_run_install_dev(
     package.add_dependency_group(group)
 
 
-def test_run_install_no_group(
-    installer: Installer,
-    locker: Locker,
-    repo: Repository,
-    package: ProjectPackage,
-    installed: CustomInstalledRepository,
-):
-    _configure_run_install_dev(locker, repo, package, installed)
-
-    installer.only_groups([])
-    installer.run()
-
-    assert installer.executor.installations_count == 0
-    assert installer.executor.updates_count == 0
-    assert installer.executor.removals_count == 0
-
-
-def test_run_install_group_only(
-    installer: Installer,
-    locker: Locker,
-    repo: Repository,
-    package: ProjectPackage,
-    installed: CustomInstalledRepository,
-):
-    _configure_run_install_dev(locker, repo, package, installed)
-
-    installer.only_groups(["dev"])
-    installer.run()
-
-    assert installer.executor.installations_count == 0
-    assert installer.executor.updates_count == 0
-    assert installer.executor.removals_count == 0
-
-
-def test_run_install_with_optional_group_not_selected(
+@pytest.mark.parametrize(
+    ("groups", "installs", "updates", "removals", "with_packages_installed"),
+    [
+        (None, 2, 0, 0, False),
+        (None, 0, 0, 1, True),
+        ([], 0, 0, 0, False),
+        ([], 0, 0, 3, True),
+        (["dev"], 1, 0, 0, False),
+        (["dev"], 0, 0, 2, True),
+        (["default"], 2, 0, 0, False),
+        (["default"], 0, 0, 1, True),
+        (["default", "dev"], 3, 0, 0, False),
+        (["default", "dev"], 0, 0, 0, True),
+    ],
+)
+def test_run_install_with_dependency_groups(
+    groups: list[str] | None,
+    installs: int,
+    updates: int,
+    removals: int,
+    with_packages_installed: bool,
     installer: Installer,
     locker: Locker,
     repo: Repository,
@@ -414,14 +402,23 @@ def test_run_install_with_optional_group_not_selected(
     installed: CustomInstalledRepository,
 ):
     _configure_run_install_dev(
-        locker, repo, package, installed, with_optional_group=True
+        locker,
+        repo,
+        package,
+        installed,
+        with_optional_group=True,
+        with_packages_installed=with_packages_installed,
     )
 
+    if groups is not None:
+        installer.only_groups(groups)
+
+    installer.requires_synchronization(True)
     installer.run()
 
-    assert installer.executor.installations_count == 0
-    assert installer.executor.updates_count == 0
-    assert installer.executor.removals_count == 0
+    assert installer.executor.installations_count == installs
+    assert installer.executor.updates_count == updates
+    assert installer.executor.removals_count == removals
 
 
 def test_run_install_does_not_remove_locked_packages_if_installed_but_not_required(
@@ -636,25 +633,6 @@ def test_run_install_removes_no_longer_locked_packages_if_installed(
     assert installer.executor.removals_count == 2
 
 
-def test_run_install_with_optional_group_selected(
-    installer: Installer,
-    locker: Locker,
-    repo: Repository,
-    package: ProjectPackage,
-    installed: CustomInstalledRepository,
-):
-    _configure_run_install_dev(
-        locker, repo, package, installed, with_optional_group=True
-    )
-
-    installer.only_groups(["default", "dev"])
-    installer.run()
-
-    assert installer.executor.installations_count == 0
-    assert installer.executor.updates_count == 0
-    assert installer.executor.removals_count == 0
-
-
 @pytest.mark.parametrize(
     "managed_reserved_package_names",
     itertools.chain(