Refactor for cluster usage

Signed-off-by: Andrey Berezin <a.berezin@yadro.com>

pytest_tests/steps/cluster_test_base.py

@@ -0,0 +1,25 @@
+import epoch
+import pytest
+from cluster import Cluster
+from neofs_testlib.shell import Shell
+
+
+# To skip adding every mandatory singleton dependency to EACH test function
+class ClusterTestBase:
+    shell: Shell
+    cluster: Cluster
+
+    @pytest.fixture(scope="session", autouse=True)
+    def fill_mandatory_dependencies(self, cluster: Cluster, client_shell: Shell):
+        ClusterTestBase.shell = client_shell
+        ClusterTestBase.cluster = cluster
+        yield
+
+    def tick_epoch(self):
+        epoch.tick_epoch(self.shell, self.cluster)
+
+    def get_epoch(self):
+        return epoch.get_epoch(self.shell, self.cluster)
+
+    def ensure_fresh_epoch(self):
+        return epoch.ensure_fresh_epoch(self.shell, self.cluster)