[DPE-8276] Add unit tests

pyproject.toml

@@ -0,0 +1,98 @@
+# Copyright 2025 Canonical Ltd.
+# See LICENSE file for licensing details.
+
+[project]
+name = "postgresql-charms-single-kernel"
+dynamic = ["version"]
+description = "Shared and reusable code for PostgreSQL-related charms"
+readme = "README.md"
+license = "Apache-2.0"
+authors = [
+    {name = "Canonical Data Platform", email = "data-platform@lists.launchpad.net"}
+]
+classifiers = [
+ "Development Status :: 3 - Alpha",
+ "Intended Audience :: Developers",
+ "Operating System :: POSIX :: Linux",
+]
+requires-python = ">=3.8,<4.0"
+
+[dependency-groups]
+lib = [
+    "ops>=2.0.0",
+    "psycopg2>=2.9.10",
+]
+format = [
+    "ruff==0.12.11"
+]
+lint = [
+    "codespell==2.4.1"
+]
+unit = [
+    "coverage[toml]==7.9.1; python_version > '3.8'",
+    "pytest>=8.3.5; python_version < '3.9'",
+    "pytest==8.4.1; python_version >= '3.9'"
+]
+
+# Testing tools configuration
+[tool.coverage.run]
+branch = true
+
+[tool.coverage.report]
+show_missing = true
+exclude_lines = [
+    "logger\\.debug"
+]
+
+[tool.pytest.ini_options]
+minversion = "6.0"
+log_cli_level = "INFO"
+
+# Linting tools configuration
+[tool.ruff]
+# preview and explicit preview are enabled for CPY001
+preview = true
+target-version = "py38"
+src = ["src", "."]
+line-length = 99
+
+[tool.ruff.lint]
+explicit-preview-rules = true
+select = ["A", "E", "W", "F", "C", "N", "D", "I001", "B", "CPY001", "RUF", "S", "SIM", "UP", "TCH"]
+extend-ignore = [
+    "D203",
+    "D204",
+    "D213",
+    "D215",
+    "D400",
+    "D404",
+    "D406",
+    "D407",
+    "D408",
+    "D409",
+    "D413",
+]
+# Ignore E501 because using black creates errors with this
+# Ignore D107 Missing docstring in __init__
+ignore = ["E501", "D107"]
+
+[tool.ruff.lint.per-file-ignores]
+"tests/*" = [
+    "D100", "D101", "D102", "D103", "D104",
+    # Asserts
+    "B011",
+    # Disable security checks for tests
+    "S",
+]
+
+[tool.ruff.lint.flake8-copyright]
+# Check for properly formatted copyright header in each file
+author = "Canonical Ltd."
+notice-rgx = "Copyright\\s\\d{4}([-,]\\d{4})*\\s+"
+min-file-size = 1
+
+[tool.ruff.lint.mccabe]
+max-complexity = 10
+
+[tool.ruff.lint.pydocstyle]
+convention = "google"

single_kernel_postgresql/__init__.py

@@ -0,0 +1,3 @@
+# Copyright 2025 Canonical Ltd.
+# See LICENSE file for licensing details.
+"""PostgreSQL Operators Single Kernel."""

single_kernel_postgresql/abstract_charm.py

@@ -0,0 +1,26 @@
+# Copyright 2025 Canonical Ltd.
+# See LICENSE file for licensing details.
+"""Skeleton for the abstract charm."""
+
+from ops.charm import CharmBase
+
+from .config.literals import SYSTEM_USERS, USER
+from .utils.postgresql import PostgreSQL
+
+
+class AbstractPostgreSQLCharm(CharmBase):
+    """An abstract PostgreSQL charm."""
+
+    def __init__(self, *args):
+        super().__init__(*args)
+
+        self.postgresql = PostgreSQL(
+            primary_host="localhost",
+            current_host="localhost",
+            user=USER,
+            # The password is hardcoded because this is an abstract charm and
+            # it meant to be used only in unit tests.
+            password="test-password",  # noqa S106
+            database="test-database",
+            system_users=SYSTEM_USERS,
+        )

single_kernel_postgresql/charmcraft.yaml

@@ -0,0 +1,22 @@
+# Copyright 2025 Canonical Ltd.
+# See LICENSE file for licensing details.
+#
+# This file is here only to run unit tests.
+type: charm
+name: postgresql-single-kernel
+title: PostgreSQL Single Kernel Charm
+summary: Placeholder charm for unit tests.
+description: Placeholder charm for unit tests.
+
+base: ubuntu@24.04
+platforms:
+  amd64:
+  arm64:
+
+peers:
+  database-peers:
+    interface: postgresql_peers
+
+provides:
+  database:
+    interface: postgresql_client

single_kernel_postgresql/config/literals.py

@@ -5,6 +5,9 @@
 This module should contain the literals used in the charms (paths, enums, etc).
 """
 
+# Relations.
+PEER = "database-peers"
+
 # Users.
 BACKUP_USER = "backup"
 MONITORING_USER = "monitoring"