diff --git a/.config/dictionary.txt b/.config/dictionary.txt
index 6169fd3..5be48b4 100644
--- a/.config/dictionary.txt
+++ b/.config/dictionary.txt
@@ -10,9 +10,11 @@ cpart
 cpath
 crepository
 csource
+delenv
 excinfo
 fileh
 fqcn
+jsonschema
 levelname
 levelno
 netcommon
@@ -23,5 +25,6 @@ setenv
 specp
 treemaker
 uninstallation
+usefixtures
 vuuid
 xmltodict
diff --git a/src/ansible_dev_environment/__main__.py b/src/ansible_dev_environment/__main__.py
index fdf08a3..28dba09 100644
--- a/src/ansible_dev_environment/__main__.py
+++ b/src/ansible_dev_environment/__main__.py
@@ -4,7 +4,7 @@
 via :command:`python -m ansible_dev_environment`.
 """
 
-from .cli import main
+from ansible_dev_environment.cli import main
 
 
 if __name__ == "__main__":
diff --git a/src/ansible_dev_environment/arg_parser.py b/src/ansible_dev_environment/arg_parser.py
index 692e62a..06724cc 100644
--- a/src/ansible_dev_environment/arg_parser.py
+++ b/src/ansible_dev_environment/arg_parser.py
@@ -200,20 +200,25 @@ def parse() -> argparse.Namespace:
         help="Uninstall a collection.",
     )
 
-    for grp in parser._action_groups:  # noqa: SLF001
-        if grp.title is None:
-            continue
-        grp.title = grp.title.capitalize()
+    _group_titles(parser)
     for subparser in subparsers.choices.values():
-        for grp in subparser._action_groups:  # noqa: SLF001
-            if grp.title is None:
-                continue
-            grp.title = grp.title.capitalize()
-    # pylint: enable=protected-access
+        _group_titles(subparser)
 
     return parser.parse_args()
 
 
+def _group_titles(parser: ArgumentParser) -> None:
+    """Set the group titles to be capitalized.
+
+    Args:
+        parser: The parser to set the group titles for
+    """
+    for group in parser._action_groups:  # noqa: SLF001
+        if group.title is None:
+            continue
+        group.title = group.title.capitalize()
+
+
 class ArgumentParser(argparse.ArgumentParser):
     """A custom argument parser."""
 
diff --git a/src/ansible_dev_environment/cli.py b/src/ansible_dev_environment/cli.py
index 0c5eeb2..99448a8 100644
--- a/src/ansible_dev_environment/cli.py
+++ b/src/ansible_dev_environment/cli.py
@@ -170,7 +170,3 @@ def main() -> None:
     cli.args_sanity()
     cli.ensure_isolated()
     cli.run()
-
-
-if __name__ == "__main__":
-    main()
diff --git a/src/ansible_dev_environment/subcommands/treemaker.py b/src/ansible_dev_environment/subcommands/treemaker.py
index 35970e8..a053f1b 100644
--- a/src/ansible_dev_environment/subcommands/treemaker.py
+++ b/src/ansible_dev_environment/subcommands/treemaker.py
@@ -2,7 +2,7 @@
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, cast
 
 from ansible_dev_environment.tree import Tree
 from ansible_dev_environment.utils import builder_introspect, collect_manifests
@@ -44,10 +44,7 @@ def run(self: TreeMaker) -> None:  # noqa: C901, PLR0912, PLR0915
             target=self._config.site_pkg_collections_path,
             venv_cache_dir=self._config.venv_cache_dir,
         )
-        tree_dict: JSONVal = {c: {} for c in collections}
-        if not isinstance(tree_dict, dict):
-            msg = "Tree dict is not a dict."
-            raise TypeError(msg)
+        tree_dict: dict[str, dict[str, JSONVal]] = {c: {} for c in collections}
 
         links: dict[str, str] = {}
         for collection_name, collection in collections.items():
@@ -65,10 +62,6 @@ def run(self: TreeMaker) -> None:  # noqa: C901, PLR0912, PLR0915
                     self._output.error(err)
                     continue
                 target = tree_dict[collection_name]
-                if not isinstance(target, dict):
-                    msg = "Tree dict is not a dict."
-                    raise TypeError(msg)
-
                 target[dep] = tree_dict[dep]
 
             docs = collection["collection_info"].get("documentation")
@@ -97,7 +90,8 @@ def run(self: TreeMaker) -> None:  # noqa: C901, PLR0912, PLR0915
 
         more_verbose = 2
         if self._config.args.verbose >= more_verbose:
-            tree = Tree(obj=tree_dict, term_features=self._config.term_features)
+            j_tree_dict = cast(JSONVal, tree_dict)
+            tree = Tree(obj=j_tree_dict, term_features=self._config.term_features)
             tree.links = links
             tree.green.extend(green)
             rendered = tree.render()
@@ -132,7 +126,7 @@ def run(self: TreeMaker) -> None:  # noqa: C901, PLR0912, PLR0915
 
 
 def add_python_reqs(
-    tree_dict: dict[str, JSONVal],
+    tree_dict: dict[str, dict[str, JSONVal]],
     collection_name: str,
     python_deps: list[str],
 ) -> None:
diff --git a/tests/integration/test_basic.py b/tests/integration/test_basic.py
index 280d3ad..cdce183 100644
--- a/tests/integration/test_basic.py
+++ b/tests/integration/test_basic.py
@@ -137,16 +137,13 @@ def test_non_local(
     assert string in captured.out
     monkeypatch.setattr(
         "sys.argv",
-        ["ade", "tree", f"--venv={tmp_path / 'venv'}"],
+        ["ade", "tree", f"--venv={tmp_path / 'venv'}", "-v"],
     )
     with pytest.raises(SystemExit):
         main()
     captured = capsys.readouterr()
-    with pytest.raises(SystemExit):
-        main()
-    captured = capsys.readouterr()
-    string = "ansible.scm\n└──ansible.utils\n\n"
-    assert string == captured.out
+    assert "ansible.scm\n├──ansible.utils" in captured.out
+    assert "├──jsonschema" in captured.out
 
 
 def test_requirements(
diff --git a/tests/test_argparser.py b/tests/test_argparser.py
new file mode 100644
index 0000000..a5ef043
--- /dev/null
+++ b/tests/test_argparser.py
@@ -0,0 +1,92 @@
+"""Tests for the arg_parser module."""
+
+import pytest
+
+from ansible_dev_environment.arg_parser import (
+    ArgumentParser,
+    CustomHelpFormatter,
+    _group_titles,
+)
+
+
+def test_no_option_string(
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    """Test an argument without an option string.
+
+    Args:
+        capsys: Pytest fixture.
+    """
+    parser = ArgumentParser(
+        formatter_class=CustomHelpFormatter,
+    )
+    parser.add_argument(
+        dest="test",
+        action="store_true",
+        help="Test this",
+    )
+    parser.print_help()
+    captured = capsys.readouterr()
+    assert "Test this" in captured.out
+
+
+def test_one_string(
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    """Test an argument without an option string.
+
+    Args:
+        capsys: Pytest fixture.
+    """
+    parser = ArgumentParser(
+        formatter_class=CustomHelpFormatter,
+    )
+    parser.add_argument(
+        "-t",
+        dest="test",
+        action="store_true",
+        help="Test this",
+    )
+    parser.print_help()
+    captured = capsys.readouterr()
+    assert "-t             Test this" in captured.out
+
+
+def test_too_many_string(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Test an argument with too many option strings.
+
+    Args:
+        monkeypatch: Pytest fixture.
+    """
+    monkeypatch.setattr("sys.argv", ["prog", "--help"])
+
+    parser = ArgumentParser(
+        formatter_class=CustomHelpFormatter,
+    )
+    parser.add_argument(
+        "-t",
+        "-test",
+        "--test",
+        action="store_true",
+        help="Test this",
+    )
+    with pytest.raises(ValueError, match="Too many option strings"):
+        parser.parse_args()
+
+
+def test_group_no_title(capsys: pytest.CaptureFixture[str]) -> None:
+    """Test a group without a title.
+
+    Args:
+        capsys: Pytest fixture.
+    """
+    parser = ArgumentParser(
+        formatter_class=CustomHelpFormatter,
+    )
+    parser.add_argument_group()
+    _group_titles(parser)
+    parser.print_help()
+    captured = capsys.readouterr()
+    assert "--help" in captured.out
diff --git a/tests/unit/conftest.py b/tests/unit/conftest.py
index 194a550..98a870e 100644
--- a/tests/unit/conftest.py
+++ b/tests/unit/conftest.py
@@ -31,3 +31,25 @@ def output(tmp_path: Path) -> Output:
         term_features=TermFeatures(color=False, links=False),
         verbosity=0,
     )
+
+
+@pytest.fixture(name="_wide_console")
+def _wide_console(monkeypatch: pytest.MonkeyPatch) -> None:
+    """Fixture to set the terminal width to 1000 to prevent wrapping.
+
+    Args:
+        monkeypatch: Pytest fixture.
+    """
+
+    def _console_width() -> int:
+        """Return a large console width.
+
+        Returns:
+            int: Console width.
+        """
+        return 1000
+
+    monkeypatch.setattr(
+        "ansible_dev_environment.output.console_width",
+        _console_width,
+    )
diff --git a/tests/unit/test_cli.py b/tests/unit/test_cli.py
new file mode 100644
index 0000000..d585774
--- /dev/null
+++ b/tests/unit/test_cli.py
@@ -0,0 +1,317 @@
+"""Test cli functionality."""
+
+from collections.abc import Generator
+from pathlib import Path
+
+import pytest
+
+from ansible_dev_environment.cli import Cli
+
+
+def main(cli: Cli) -> None:
+    """Stub main function for testing.
+
+    Args:
+        cli: Cli object.
+    """
+    cli.parse_args()
+    cli.init_output()
+    cli.args_sanity()
+    cli.ensure_isolated()
+
+
+def test_cpi(monkeypatch: pytest.MonkeyPatch) -> None:
+    """Test the cpi option.
+
+    Args:
+        monkeypatch: Pytest fixture.
+    """
+    monkeypatch.setattr("sys.argv", ["ansible-dev-environment", "install", "--cpi"])
+    cli = Cli()
+    cli.parse_args()
+    assert cli.args.requirement.parts[-3:] == (
+        "ansible-dev-environment",
+        ".config",
+        "source-requirements.yml",
+    )
+
+
+def test_tty(monkeypatch: pytest.MonkeyPatch) -> None:
+    """Test term features with tty.
+
+    Args:
+        monkeypatch: Pytest fixture.
+    """
+    monkeypatch.setattr("sys.stdout.isatty", (lambda: True))
+    monkeypatch.setattr("os.environ", {"NO_COLOR": ""})
+    monkeypatch.setattr("sys.argv", ["ansible-dev-environment", "install"])
+    cli = Cli()
+    cli.parse_args()
+    cli.init_output()
+    assert cli.output.term_features.color
+    assert cli.output.term_features.links
+
+
+@pytest.mark.usefixtures("_wide_console")
+def test_missing_requirements(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    """Test the missing requirements file.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+        tmp_path: Pytest fixture.
+    """
+    requirements_file = tmp_path / "requirements.yml"
+    monkeypatch.setattr(
+        "sys.argv",
+        ["ansible-dev-environment", "install", "-r", str(requirements_file)],
+    )
+    match = f"Requirements file not found: {requirements_file}"
+    cli = Cli()
+    with pytest.raises(SystemExit):
+        main(cli)
+    captured = capsys.readouterr()
+    assert match in captured.err
+
+
+def test_editable_many(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Test the editable option with too many arguments.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+    """
+    monkeypatch.setattr(
+        "sys.argv",
+        ["ansible-dev-environment", "install", "--venv", "venv", "-e", "one", "two"],
+    )
+    cli = Cli()
+    cli.parse_args()
+    with pytest.raises(SystemExit):
+        main(cli)
+    captured = capsys.readouterr()
+    assert "Editable can only be used with a single collection specifier." in captured.err
+
+
+def test_editable_requirements(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    """Test the editable option with requirements file.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+        tmp_path: Pytest fixture.
+    """
+    requirements_file = tmp_path / "requirements.yml"
+    requirements_file.touch()
+    monkeypatch.setattr(
+        "sys.argv",
+        ["ansible-dev-environment", "install", "-r", str(requirements_file), "-e"],
+    )
+    cli = Cli()
+    cli.parse_args()
+    with pytest.raises(SystemExit):
+        main(cli)
+    captured = capsys.readouterr()
+    assert "Editable can not be used with a requirements file." in captured.err
+
+
+@pytest.mark.parametrize(
+    "env_var",
+    (
+        "ANSIBLE_COLLECTIONS_PATHS",
+        "ANSIBLE_COLLECTION_PATH",
+    ),
+)
+def test_acp_env_var_set(
+    env_var: str,
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Test the ansible collection path environment variable set.
+
+    Args:
+        env_var: Environment variable name.
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+    """
+    monkeypatch.setenv(env_var, "test")
+    monkeypatch.setattr("sys.argv", ["ansible-dev-environment", "install"])
+    cli = Cli()
+    cli.parse_args()
+    with pytest.raises(SystemExit):
+        main(cli)
+    captured = capsys.readouterr()
+    assert f"{env_var} is set" in captured.err
+
+
+@pytest.mark.usefixtures("_wide_console")
+def test_collections_in_home(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+    tmp_path: Path,
+) -> None:
+    """Test the collections in home directory.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+        tmp_path: Pytest fixture.
+    """
+    monkeypatch.setattr(
+        "sys.argv",
+        ["ansible-dev-environment", "install", "--venv", "venv"],
+    )
+    monkeypatch.setenv("HOME", str(tmp_path))
+    collection_root = tmp_path / ".ansible" / "collections" / "ansible_collections"
+    (collection_root / "ansible" / "utils").mkdir(parents=True)
+    cli = Cli()
+    cli.parse_args()
+    with pytest.raises(SystemExit):
+        main(cli)
+    captured = capsys.readouterr()
+    msg = f"Collections found in {collection_root}"
+    assert msg in captured.err
+
+
+def test_collections_in_user(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Test the collections in user directory.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+    """
+    usr_path = Path("/usr/share/ansible/collections")
+    exists = Path.exists
+
+    def _exists(self: Path) -> bool:
+        """Patch the exists method.
+
+        Args:
+            self: Path object.
+
+        Returns:
+            bool: True if the path exists.
+        """
+        if self == usr_path:
+            return True
+        return exists(self)
+
+    monkeypatch.setattr(Path, "exists", _exists)
+
+    iterdir = Path.iterdir
+
+    def _iterdir(self: Path) -> list[Path] | Generator[Path, None, None]:
+        """Patch the iterdir method.
+
+        Args:
+            self: Path object.
+
+        Returns:
+            List of paths or generator.
+        """
+        if self == usr_path:
+            return [usr_path / "ansible_collections"]
+        return iterdir(self)
+
+    monkeypatch.setattr(Path, "iterdir", _iterdir)
+
+    monkeypatch.setattr(
+        "sys.argv",
+        ["ansible-dev-environment", "install", "--venv", "venv"],
+    )
+    cli = Cli()
+    cli.parse_args()
+    with pytest.raises(SystemExit):
+        main(cli)
+    captured = capsys.readouterr()
+    msg = f"Collections found in {usr_path}"
+    assert msg in captured.err
+
+
+def test_no_venv_specified(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Test no virtual environment specified.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+    """
+    monkeypatch.setattr(
+        "sys.argv",
+        ["ansible-dev-environment", "install"],
+    )
+    monkeypatch.delenv("VIRTUAL_ENV", raising=False)
+    cli = Cli()
+    cli.parse_args()
+    with pytest.raises(SystemExit):
+        main(cli)
+    captured = capsys.readouterr()
+    assert "Unable to use user site packages directory" in captured.err
+
+
+def test_exit_code_one(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Test exit code one.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+    """
+    monkeypatch.setattr(
+        "sys.argv",
+        ["ansible-dev-environment", "install"],
+    )
+    cli = Cli()
+    cli.parse_args()
+    cli.init_output()
+    cli.output.error("Test error")
+    with pytest.raises(SystemExit) as excinfo:
+        cli._exit()
+    expected = 1
+    assert excinfo.value.code == expected
+    captured = capsys.readouterr()
+    assert "Test error" in captured.err
+
+
+def test_exit_code_two(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """Test exit code two.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+    """
+    monkeypatch.setattr(
+        "sys.argv",
+        ["ansible-dev-environment", "install"],
+    )
+    cli = Cli()
+    cli.parse_args()
+    cli.init_output()
+    cli.output.warning("Test warning")
+    with pytest.raises(SystemExit) as excinfo:
+        cli._exit()
+    expected = 2
+    assert excinfo.value.code == expected
+    captured = capsys.readouterr()
+    assert "Test warning" in captured.out
diff --git a/tests/unit/test_main.py b/tests/unit/test_main.py
new file mode 100644
index 0000000..a016b66
--- /dev/null
+++ b/tests/unit/test_main.py
@@ -0,0 +1,18 @@
+"""Test the main file."""
+
+import runpy
+
+import pytest
+
+
+def test_main(capsys: pytest.CaptureFixture[str]) -> None:
+    """Test the main file.
+
+    Args:
+        capsys: Capture stdout and stderr
+    """
+    with pytest.raises(SystemExit):
+        runpy.run_module("ansible_dev_environment", run_name="__main__", alter_sys=True)
+
+    captured = capsys.readouterr()
+    assert "the following arguments are required" in captured.err
diff --git a/tests/unit/test_tree.py b/tests/unit/test_tree.py
index fda3712..a02622a 100644
--- a/tests/unit/test_tree.py
+++ b/tests/unit/test_tree.py
@@ -5,6 +5,8 @@
 
 from typing import TYPE_CHECKING
 
+import pytest
+
 from ansible_dev_environment.tree import Tree
 from ansible_dev_environment.utils import TermFeatures
 
@@ -150,3 +152,11 @@ def test_tree_color() -> None:
     tree.links = {"2": "http://red.ht"}
     rendered = tree.render().splitlines()
     assert rendered == expected
+
+
+def test_tree_fail() -> None:
+    """Test a tree failure."""
+    term_features = TermFeatures(color=False, links=False)
+    tree = Tree(obj=(1, 2, 3), term_features=term_features)  # type: ignore[arg-type]
+    with pytest.raises(TypeError, match="Invalid type <class 'tuple'>"):
+        tree.render()
diff --git a/tests/unit/test_treemaker.py b/tests/unit/test_treemaker.py
new file mode 100644
index 0000000..7f09f88
--- /dev/null
+++ b/tests/unit/test_treemaker.py
@@ -0,0 +1,276 @@
+"""Test the treemaker module."""
+
+from argparse import Namespace
+from pathlib import Path
+from venv import EnvBuilder
+
+import pytest
+
+from ansible_dev_environment.config import Config
+from ansible_dev_environment.output import Output
+from ansible_dev_environment.subcommands.treemaker import TreeMaker
+from ansible_dev_environment.utils import JSONVal
+
+
+def test_tree_empty(
+    capsys: pytest.CaptureFixture[str],
+    output: Output,
+    tmp_path: Path,
+) -> None:
+    """Test tree_not_dict.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        output: Output class object.
+        tmp_path: Pytest fixture.
+    """
+    venv_path = tmp_path / "venv"
+    EnvBuilder().create(venv_path)
+
+    args = Namespace(
+        venv=venv_path,
+        verbose=0,
+    )
+    config = Config(args=args, output=output, term_features=output.term_features)
+    config.init()
+    treemaker = TreeMaker(config=config, output=output)
+    treemaker.run()
+    captured = capsys.readouterr()
+    assert captured.out == "\n\n"
+    assert not captured.err
+
+
+def test_tree_malformed_info(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+    output: Output,
+    tmp_path: Path,
+) -> None:
+    """Test malformed collection info.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+        output: Output class object.
+        tmp_path: Pytest fixture.
+    """
+    venv_path = tmp_path / "venv"
+    EnvBuilder().create(venv_path)
+
+    args = Namespace(
+        venv=venv_path,
+        verbose=0,
+    )
+
+    def collect_manifests(
+        target: Path,
+        venv_cache_dir: Path,
+    ) -> dict[str, dict[str, JSONVal]]:
+        """Return a malformed collection info.
+
+        Args:
+            target: Target path.
+            venv_cache_dir: Venv cache directory.
+        <<<<<<< HEAD
+
+        Returns:
+            Collection info.
+        =======
+        >>>>>>> 556acba (Add some tests)
+        """
+        assert target
+        assert venv_cache_dir
+        return {
+            "collection_one": {
+                "collection_info": "malformed",
+            },
+        }
+
+    monkeypatch.setattr(
+        "ansible_dev_environment.subcommands.treemaker.collect_manifests",
+        collect_manifests,
+    )
+    config = Config(args=args, output=output, term_features=output.term_features)
+    config.init()
+    treemaker = TreeMaker(config=config, output=output)
+    treemaker.run()
+    captured = capsys.readouterr()
+    assert "Collection collection_one has malformed metadata." in captured.err
+
+
+def test_tree_malformed_deps(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+    output: Output,
+    tmp_path: Path,
+) -> None:
+    """Test malformed collection deps.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+        output: Output class object.
+        tmp_path: Pytest fixture.
+    """
+    venv_path = tmp_path / "venv"
+    EnvBuilder().create(venv_path)
+
+    args = Namespace(
+        venv=venv_path,
+        verbose=0,
+    )
+
+    def collect_manifests(
+        target: Path,
+        venv_cache_dir: Path,
+    ) -> dict[str, dict[str, JSONVal]]:
+        """Return a malformed collection info.
+
+        Args:
+            target: Target path.
+            venv_cache_dir: Venv cache directory.
+        <<<<<<< HEAD
+
+        Returns:
+            Collection info.
+        =======
+        >>>>>>> 556acba (Add some tests)
+        """
+        assert target
+        assert venv_cache_dir
+        return {
+            "collection_one": {
+                "collection_info": {
+                    "dependencies": "malformed",
+                },
+            },
+        }
+
+    monkeypatch.setattr(
+        "ansible_dev_environment.subcommands.treemaker.collect_manifests",
+        collect_manifests,
+    )
+    config = Config(args=args, output=output, term_features=output.term_features)
+    config.init()
+    treemaker = TreeMaker(config=config, output=output)
+    treemaker.run()
+    captured = capsys.readouterr()
+    assert "Collection collection_one has malformed metadata." in captured.err
+
+
+def test_tree_malformed_deps_not_string(
+    capsys: pytest.CaptureFixture[str],
+    monkeypatch: pytest.MonkeyPatch,
+    output: Output,
+    tmp_path: Path,
+) -> None:
+    """Test malformed collection deps.
+
+    Args:
+        capsys: Pytest stdout capture fixture.
+        monkeypatch: Pytest fixture.
+        output: Output class object.
+        tmp_path: Pytest fixture.
+    """
+    venv_path = tmp_path / "venv"
+    EnvBuilder().create(venv_path)
+
+    args = Namespace(
+        venv=venv_path,
+        verbose=0,
+    )
+
+    def collect_manifests(
+        target: Path,
+        venv_cache_dir: Path,
+    ) -> dict[str, dict[str, dict[str, dict[int, int]]]]:
+        """Return a malformed collection info.
+
+        Args:
+            target: Target path.
+            venv_cache_dir: Venv cache directory.
+        <<<<<<< HEAD
+
+        Returns:
+            Collection info.
+        =======
+        >>>>>>> 556acba (Add some tests)
+        """
+        assert target
+        assert venv_cache_dir
+        return {
+            "collection_one": {
+                "collection_info": {
+                    "dependencies": {1: 2},
+                },
+            },
+        }
+
+    monkeypatch.setattr(
+        "ansible_dev_environment.subcommands.treemaker.collect_manifests",
+        collect_manifests,
+    )
+    config = Config(args=args, output=output, term_features=output.term_features)
+    config.init()
+    treemaker = TreeMaker(config=config, output=output)
+    treemaker.run()
+    captured = capsys.readouterr()
+    assert "Collection collection_one has malformed dependency." in captured.err
+
+
+def test_tree_malformed_repo_not_string(
+    monkeypatch: pytest.MonkeyPatch,
+    output: Output,
+    tmp_path: Path,
+) -> None:
+    """Test malformed collection repo.
+
+    Args:
+        monkeypatch: Pytest fixture.
+        output: Output class object.
+        tmp_path: Pytest fixture.
+    """
+    venv_path = tmp_path / "venv"
+    EnvBuilder().create(venv_path)
+
+    args = Namespace(
+        venv=venv_path,
+        verbose=0,
+    )
+
+    def collect_manifests(
+        target: Path,
+        venv_cache_dir: Path,
+    ) -> dict[str, dict[str, JSONVal]]:
+        """Return a malformed collection info.
+
+        Args:
+            target: Target path.
+            venv_cache_dir: Venv cache directory.
+        <<<<<<< HEAD
+
+        Returns:
+            Collection info.
+        =======
+        >>>>>>> 556acba (Add some tests)
+        """
+        assert target
+        assert venv_cache_dir
+        return {
+            "collection_one": {
+                "collection_info": {
+                    "dependencies": {},
+                    "repository": True,
+                },
+            },
+        }
+
+    monkeypatch.setattr(
+        "ansible_dev_environment.subcommands.treemaker.collect_manifests",
+        collect_manifests,
+    )
+    config = Config(args=args, output=output, term_features=output.term_features)
+    config.init()
+    treemaker = TreeMaker(config=config, output=output)
+    with pytest.raises(TypeError, match="Link is not a string."):
+        treemaker.run()