diff --git a/.copier-answers.yml b/.copier-answers.yml
index f990ec6..4b717f9 100644
--- a/.copier-answers.yml
+++ b/.copier-answers.yml
@@ -2,7 +2,7 @@
 # Answer file maintained by Copier for: https://github.com/KyleKing/mdformat-plugin-template
 # DO NOT MODIFY THIS FILE. Edit by re-running copier and changing responses to the questions
 # Check into version control.
-_commit: 0.1.2
+_commit: 0.1.3
 _src_path: gh:KyleKing/mdformat-plugin-template
 author_email: dev.act.kyle@gmail.com
 author_name: Kyle King
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index c513a24..3c03568 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -14,7 +14,7 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: 3.12
-      - uses: pre-commit/action@v3
+      - uses: pre-commit/action@v3.0.1
   tests:
     runs-on: ${{ matrix.os }}
     strategy:
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index d705910..78e5c4b 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -73,6 +73,6 @@ export eval $(envchain FLIT env | grep FLIT_PASSWORD=)
 flit publish
 ```
 
-or trigger the GitHub Action job, by creating a release with a tag equal to the version, e.g. `v0.0.1` and updating the version in `mdformat_admon/__init__.py`.
+or trigger the GitHub Action job, by creating a release with a tag equal to the version, e.g. `v0.0.1` and updating the version in `mdformat_gfm_alerts/__init__.py`.
 
 Note, this requires generating an API key on PyPi and adding it to the repository `Settings/Secrets`, under the name `PYPI_KEY`.
diff --git a/pyproject.toml b/pyproject.toml
index 1feae86..49b9db6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -29,6 +29,7 @@ gfm_alerts = "mdformat_gfm_alerts"
 dev = ["pre-commit"]
 test = [
   "pytest >= 7.4.4",
+  "pytest-beartype >= 0.0.2",
   "pytest-cov >= 4.1.0",
 ]
 
@@ -44,7 +45,7 @@ ignore_patterns = []
 now = true
 patterns = ["*.md", "*.py"]
 runner = "tox"
-runner_args = ["-e", "py38"]
+runner_args = ["-e", "py38-beartype"]
 
 [tool.tomlsort]
 all = true
diff --git a/tests/helpers.py b/tests/helpers.py
index 3197c8b..c04386c 100644
--- a/tests/helpers.py
+++ b/tests/helpers.py
@@ -1,21 +1,32 @@
 """Test Helpers."""
 
+from __future__ import annotations
+
+import re
+
 _SHOW_TEXT = True  # PLANNED: Make configurable based on pytest CLI
 
 
-def _print(content: str, show_whitespace: bool) -> None:
-    if show_whitespace:
-        raise NotImplementedError("To use, port logic from `mdformat_mkdocs`")
+def separate_indent(line: str) -> tuple[str, str]:
+    """Separate leading indent from content. Also used by the test suite."""
+    re_indent = re.compile(r"(?P<indent>\s*)(?P<content>[^\s]?.*)")
+    match = re_indent.match(line)
+    assert match is not None  # for pyright
+    return (match["indent"], match["content"])
 
+
+def _print(content: str, show_whitespace: bool) -> None:
     for line in content.split("\n"):
-        print(line)
+        indent, content = separate_indent(line)
+        visible_indents = indent.replace(" ", "→").replace("\t", "➤")
+        print((visible_indents if show_whitespace else indent) + content)
 
 
 def print_text(output: str, expected: str, show_whitespace: bool = False) -> None:
     """Conditionall print text for debugging."""
     if _SHOW_TEXT:
         print("--  Output  --")
-        _print(output.strip(), show_whitespace)
+        _print(output, show_whitespace)
         print("-- Expected --")
-        _print(expected.strip(), show_whitespace)
+        _print(expected, show_whitespace)
         print("--  <End>   --")
diff --git a/tox.ini b/tox.ini
index 56fe852..a1e7772 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 envlist =
-    py{38}
+    py{38}-beartype
     py{312}-cov
     py{312}-pre-commit
     py{38}-hook
@@ -9,9 +9,9 @@ envlist =
 isolated_build = True
 skip_missing_interpreters = False
 
-[testenv:py{38}]
+[testenv:py{38}-beartype]
 extras = test
-commands = pytest {posargs} --ff --nf -vv
+commands = pytest {posargs} --ff --nf -vv --exitfirst --beartype-packages='mdformat_gfm_alerts'
 
 [testenv:py{312}-cov]
 extras = test