Add initial functional tests for dependency-groups

This initial suite of tests is modeled fairly closely on existing
tests for requirements files.

Tests cover the following cases:
- installing an empty dependency group (and nothing else)
- installing from a simple / straightforward group
- installing from multiple groups in a single command
- normalizing names from the CLI and pyproject.toml to match
- applying a constraints file to a dependency-group install

Author: sirosen

tests/functional/test_install.py

@@ -318,6 +318,21 @@ def test_install_exit_status_code_when_blank_requirements_file(
     script.pip("install", "-r", "blank.txt")
 
 
+def test_install_exit_status_code_when_empty_dependency_group(
+    script: PipTestEnvironment,
+) -> None:
+    """
+    Test install exit status code is 0 when empty dependency group specified
+    """
+    script.scratch_path.joinpath("pyproject.toml").write_text(
+        """\
+[dependency-groups]
+empty = []
+"""
+    )
+    script.pip("install", "--group", "empty")
+
+
 @pytest.mark.network
 def test_basic_install_from_pypi(script: PipTestEnvironment) -> None:
     """

tests/functional/test_install_reqs.py

@@ -93,6 +93,75 @@ def test_requirements_file(script: PipTestEnvironment) -> None:
     assert result.files_created[script.site_packages / fn].dir
 
 
+@pytest.mark.network
+def test_dependency_group(script: PipTestEnvironment) -> None:
+    """
+    Test installing from a dependency group.
+
+    """
+    pyproject = script.scratch_path / "pyproject.toml"
+    pyproject.write_text(
+        textwrap.dedent(
+            """\
+            [dependency-groups]
+            initools = [
+                "INITools==0.2",
+                "peppercorn<=0.6",
+            ]
+            """
+        )
+    )
+    result = script.pip("install", "--group", "initools")
+    result.did_create(script.site_packages / "INITools-0.2.dist-info")
+    result.did_create(script.site_packages / "initools")
+    assert result.files_created[script.site_packages / "peppercorn"].dir
+    assert result.files_created[script.site_packages / "peppercorn-0.6.dist-info"].dir
+
+
+@pytest.mark.network
+def test_multiple_dependency_groups(script: PipTestEnvironment) -> None:
+    """
+    Test installing from two dependency groups simultaneously.
+
+    """
+    pyproject = script.scratch_path / "pyproject.toml"
+    pyproject.write_text(
+        textwrap.dedent(
+            """\
+            [dependency-groups]
+            initools = ["INITools==0.2"]
+            peppercorn = ["peppercorn<=0.6"]
+            """
+        )
+    )
+    result = script.pip("install", "--group", "initools", "--group", "peppercorn")
+    result.did_create(script.site_packages / "INITools-0.2.dist-info")
+    result.did_create(script.site_packages / "initools")
+    assert result.files_created[script.site_packages / "peppercorn"].dir
+    assert result.files_created[script.site_packages / "peppercorn-0.6.dist-info"].dir
+
+
+@pytest.mark.network
+def test_dependency_group_with_non_normalized_name(script: PipTestEnvironment) -> None:
+    """
+    Test installing from a dependency group with a non-normalized name, verifying that
+    the pyproject.toml content and CLI arg are normalized to match.
+
+    """
+    pyproject = script.scratch_path / "pyproject.toml"
+    pyproject.write_text(
+        textwrap.dedent(
+            """\
+            [dependency-groups]
+            INITOOLS = ["INITools==0.2"]
+            """
+        )
+    )
+    result = script.pip("install", "--group", "IniTools")
+    result.did_create(script.site_packages / "INITools-0.2.dist-info")
+    result.did_create(script.site_packages / "initools")
+
+
 def test_schema_check_in_requirements_file(script: PipTestEnvironment) -> None:
     """
     Test installing from a requirements file with an invalid vcs schema..
@@ -212,6 +281,32 @@ def test_package_in_constraints_and_dependencies(
     assert "installed TopoRequires-0.0.1" in result.stdout
 
 
+def test_constraints_apply_to_dependency_groups(
+    script: PipTestEnvironment, data: TestData
+) -> None:
+    script.scratch_path.joinpath("constraints.txt").write_text("TopoRequires==0.0.1")
+    pyproject = script.scratch_path / "pyproject.toml"
+    pyproject.write_text(
+        textwrap.dedent(
+            """\
+            [dependency-groups]
+            mylibs = ["TopoRequires2"]
+            """
+        )
+    )
+    result = script.pip(
+        "install",
+        "--no-index",
+        "-f",
+        data.find_links,
+        "-c",
+        script.scratch_path / "constraints.txt",
+        "--group",
+        "mylibs",
+    )
+    assert "installed TopoRequires-0.0.1" in result.stdout
+
+
 def test_multiple_constraints_files(script: PipTestEnvironment, data: TestData) -> None:
     script.scratch_path.joinpath("outer.txt").write_text("-c inner.txt")
     script.scratch_path.joinpath("inner.txt").write_text("Upper==1.0")