docs: add project guidelines (#7)

### Summary of Changes

Add guidelines for documentation, tests, and code style.

docs/development/environment.md

@@ -6,7 +6,7 @@ This document describes how to configure and use your development environment.
 
 You must complete these steps once before you can start setting up the project itself:
 
-1. Install [Python 3.10](https://www.python.org/downloads/).
+1. Install [Python 3.11](https://www.python.org/downloads/).
 2. Verify that `python` can be launched by running this command in a **new** terminal:
     ```shell
     python --version

docs/development/project_guidelines.md

@@ -0,0 +1,245 @@
+# Project Guidelines
+
+This document describes general guidelines for the Safe-DS Runner.
+
+## Docstrings
+
+The docstrings **should** use the [numpydoc](https://numpydoc.readthedocs.io/en/latest/format.html) format. The
+descriptions **should not** start with "this" and **should** use imperative mood. Refer to the subsections below for
+more details on how to document specific API elements.
+
+!!! success "**DO**:"
+
+    ```py
+    def add_ints(a: int, b: int) -> int:
+        """Add two integers."""
+        return a + b
+    ```
+
+!!! failure "**DON'T**:"
+
+    ```py
+    def add_ints(a: int, b: int) -> int:
+        """This function adds two integers."""
+        return a + b
+    ```
+
+!!! failure "**DON'T**:"
+
+    ```py
+    def add_ints(a: int, b: int) -> int:
+        """Adds two integers."""
+        return a + b
+    ```
+
+!!! success "**DO**:"
+
+    ```py
+    def __init__(self, data: Mapping[str, Any] | None = None) -> None:
+        """
+        data : Mapping[str, Any] | None
+        """
+    ```
+
+!!! failure "**DON'T**:"
+
+    ```py
+    def __init__(self, data: Optional[Mapping[str, Any]] = None) -> None:
+        """
+        data : Optional[Mapping[str, Any]]
+        """
+    ```
+
+!!! failure "**DON'T**:"
+
+    ```py
+    def __init__(self, data: Mapping[str, Any] | None = None) -> None:
+        """
+        data : Optional[Mapping[str, Any]]
+        """
+    ```
+
+### Modules
+
+All modules should have
+
+* a one-line description ([short summary][short-summary-section]),
+* a longer description if needed ([extended summary][extended-summary-section]).
+
+Example:
+
+```py
+"""Containers for tabular data."""
+```
+
+### Classes
+
+All classes should have
+
+* a one-line description ([short summary][short-summary-section]),
+* a longer description if needed ([extended summary][extended-summary-section])
+* a description of the parameters of their `__init__` method ([`Parameters` section][parameters-section]),
+* examples that show how to use them correctly ([`Examples` section][examples-section]).
+
+Example:
+
+```py
+"""
+A row is a collection of named values.
+
+Parameters
+----------
+data : Mapping[str, Any] | None
+    The data. If None, an empty row is created.
+
+Examples
+--------
+>>> from safeds.data.tabular.containers import Row
+>>> row = Row({"a": 1, "b": 2})
+"""
+```
+
+### Functions
+
+All functions should have
+
+* a one-line description ([short summary][short-summary-section]),
+* a longer description if needed ([extended summary][extended-summary-section])
+* a description of their parameters ([`Parameters` section][parameters-section]),
+* a description of their results ([`Returns` section][returns-section]),
+* a description of any exceptions that may be raised and under which conditions that may
+  happen ([`Raises` section][raises-section]),
+* a description of any warnings that may be issued and under which conditions that may
+  happen ([`Warns` section][warns-section]),
+* examples that show how to use them correctly ([`Examples` section][examples-section]).
+
+Example:
+
+```py
+"""
+Return the value of a specified column.
+
+Parameters
+----------
+column_name : str
+    The column name.
+
+Returns
+-------
+value : Any
+    The column value.
+
+Raises
+------
+UnknownColumnNameError
+    If the row does not contain the specified column.
+
+Examples
+--------
+>>> from safeds.data.tabular.containers import Row
+>>> row = Row({"a": 1, "b": 2})
+>>> row.get_value("a")
+1
+"""
+```
+
+## Tests
+
+We aim for 100% line coverage, so automated tests should be added for any new function.
+
+### File structure
+
+Tests belong in the [`tests`][tests-folder] folder. The file structure in the tests folder should mirror the file
+structure of the [`src`][src-folder] folder.
+
+### Naming
+
+Names of test functions shall start with `test_should_` followed by a description of the expected behaviour,
+e.g. `test_should_add_column`.
+
+!!! success "**DO**:"
+
+    ```py
+    def test_should_raise_if_less_than_or_equal_to_0(self, number_of_trees) -> None:
+        with pytest.raises(ValueError, match="The parameter 'number_of_trees' has to be greater than 0."):
+            ...
+    ```
+
+!!! failure "**DON'T**:"
+
+    ```py
+    def test_value_error(self, number_of_trees) -> None:
+        with pytest.raises(ValueError, match="The parameter 'number_of_trees' has to be greater than 0."):
+            ...
+    ```
+
+### Parametrization
+
+Tests should be parametrized using `@pytest.mark.parametrize`, even if there is only a single test case. This makes it
+easier to add new test cases in the future. Test cases should be given descriptive IDs.
+
+!!! success "**DO**:"
+
+    ```py
+    @pytest.mark.parametrize("number_of_trees", [0, -1], ids=["zero", "negative"])
+    def test_should_raise_if_less_than_or_equal_to_0(self, number_of_trees) -> None:
+        with pytest.raises(ValueError, match="The parameter 'number_of_trees' has to be greater than 0."):
+            RandomForest(number_of_trees=number_of_trees)
+    ```
+
+!!! failure "**DON'T**:"
+
+    ```py
+    def test_should_raise_if_less_than_0(self, number_of_trees) -> None:
+        with pytest.raises(ValueError, match="The parameter 'number_of_trees' has to be greater than 0."):
+            RandomForest(number_of_trees=-1)
+
+    def test_should_raise_if_equal_to_0(self, number_of_trees) -> None:
+        with pytest.raises(ValueError, match="The parameter 'number_of_trees' has to be greater than 0."):
+            RandomForest(number_of_trees=0)
+    ```
+
+## Code style
+
+### Consistency
+
+If there is more than one way to solve a particular task, check how it has been solved at other places in the codebase
+and stick to that solution.
+
+### Sort exported classes in `__init__.py`
+
+Classes defined in a module that other classes shall be able to import must be defined in a list named `__all__` in the
+module's `__init__.py` file. This list should be sorted alphabetically, to reduce the likelihood of merge conflicts when
+adding new classes to it.
+
+!!! success "**DO**:"
+
+    ```py
+    __all__ = [
+        "Column",
+        "Row",
+        "Table",
+        "TaggedTable",
+    ]
+    ```
+
+!!! failure "**DON'T**:"
+
+    ```py
+    __all__ = [
+        "Table",
+        "TaggedTable",
+        "Column",
+        "Row",
+    ]
+    ```
+
+[src-folder]: https://github.com/Safe-DS/Library/tree/main/src
+[tests-folder]: https://github.com/Safe-DS/Library/tree/main/tests
+[short-summary-section]: https://numpydoc.readthedocs.io/en/latest/format.html#short-summary
+[extended-summary-section]: https://numpydoc.readthedocs.io/en/latest/format.html#extended-summary
+[parameters-section]: https://numpydoc.readthedocs.io/en/latest/format.html#parameters
+[returns-section]: https://numpydoc.readthedocs.io/en/latest/format.html#returns
+[raises-section]: https://numpydoc.readthedocs.io/en/latest/format.html#raises
+[warns-section]: https://numpydoc.readthedocs.io/en/latest/format.html#warns
+[examples-section]: https://numpydoc.readthedocs.io/en/latest/format.html#examples

mkdocs.yml

@@ -11,7 +11,8 @@ nav:
       - Changelog: CHANGELOG.md
   - Development:
       - Environment: development/environment.md
-      - Contributing: https://github.com/Safe-DS/Runner/contribute
+      - Project Guidelines: development/project_guidelines.md
+      - Contributing 🌐: https://github.com/Safe-DS/Runner/contribute
 
 # Configuration of MkDocs & Material for MkDocs --------------------------------