diff --git a/.github/workflows/ruff.yaml b/.github/workflows/ruff.yaml
index caedbfd..e19a5d1 100644
--- a/.github/workflows/ruff.yaml
+++ b/.github/workflows/ruff.yaml
@@ -5,7 +5,7 @@ on:
   pull_request:
 
 jobs:
-  black:
+  ruff:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
diff --git a/tests/assets/example/models.py b/tests/assets/example/models.py
index 47c17d1..7b879c6 100644
--- a/tests/assets/example/models.py
+++ b/tests/assets/example/models.py
@@ -21,7 +21,7 @@ class Post(Base):
     id = mapped_column(Uuid, primary_key=True, default=uuid4())
     author = mapped_column(ForeignKey(User.id), nullable=False)
     created = mapped_column(DateTime, nullable=False, default=datetime.now(UTC))
-    live = mapped_column(Boolean, default=False)
+    live = mapped_column(Boolean, default=False, comment="True if post is published")
     content = mapped_column(Text, default="")
 
 
diff --git a/tests/conftest.py b/tests/conftest.py
index 216493e..aa19311 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,4 +1,6 @@
 import os
+import shutil
+import tempfile
 from datetime import UTC, datetime
 from pathlib import Path
 from uuid import uuid4
@@ -43,4 +45,7 @@ class Comment(Base):
 
 @pytest.fixture
 def package_path():
-    return Path(os.path.dirname(os.path.realpath(__file__))) / "assets"
+    template_path = Path(os.path.dirname(os.path.realpath(__file__))) / "assets"
+    with tempfile.TemporaryDirectory() as package_path:
+        shutil.copytree(template_path, package_path, dirs_exist_ok=True)
+        yield Path(package_path)
diff --git a/tests/test_cli.py b/tests/test_cli.py
index f51ef0a..450c05c 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -2,27 +2,43 @@
 
 from paracelsus.cli import app
 
+from .utils import mermaid_assert
+
 runner = CliRunner()
 
 
 def test_graph(package_path):
     result = runner.invoke(
-        app, ["graph", "example.base:Base", "--import-module", "example.models", "--python-dir", str(package_path)]
+        app,
+        [
+            "graph",
+            "example.base:Base",
+            "--import-module",
+            "example.models",
+            "--python-dir",
+            str(package_path),
+        ],
     )
 
     assert result.exit_code == 0
+    mermaid_assert(result.stdout)
 
-    assert "users {" in result.stdout
-    assert "posts {" in result.stdout
-    assert "comments {" in result.stdout
 
-    assert "users ||--o{ posts : author" in result.stdout
-    assert "posts ||--o{ comments : post" in result.stdout
-    assert "users ||--o{ comments : author" in result.stdout
-
-    assert "CHAR(32) author FK" in result.stdout
-    assert 'CHAR(32) post FK "nullable"' in result.stdout
-    assert "DATETIME created" in result.stdout
+def test_inject_check(package_path):
+    result = runner.invoke(
+        app,
+        [
+            "inject",
+            str(package_path / "README.md"),
+            "example.base:Base",
+            "--import-module",
+            "example.models",
+            "--python-dir",
+            str(package_path),
+            "--check",
+        ],
+    )
+    assert result.exit_code == 1
 
 
 def test_inject(package_path):
@@ -36,14 +52,15 @@ def test_inject(package_path):
             "example.models",
             "--python-dir",
             str(package_path),
-            "--check",
         ],
     )
+    assert result.exit_code == 0
 
-    assert result.exit_code == 1
+    with open(package_path / "README.md") as fp:
+        readme = fp.read()
+        mermaid_assert(readme)
 
 
 def test_version():
     result = runner.invoke(app, ["version"])
-
     assert result.exit_code == 0
diff --git a/tests/test_graph.py b/tests/test_graph.py
index f588ad0..8977e58 100644
--- a/tests/test_graph.py
+++ b/tests/test_graph.py
@@ -1,17 +1,8 @@
 from paracelsus.graph import get_graph_string
 
+from .utils import mermaid_assert
+
 
 def test_get_graph_string(package_path):
     graph_string = get_graph_string("example.base:Base", ["example.models"], [package_path], "mermaid")
-
-    assert "users {" in graph_string
-    assert "posts {" in graph_string
-    assert "comments {" in graph_string
-
-    assert "users ||--o{ posts : author" in graph_string
-    assert "posts ||--o{ comments : post" in graph_string
-    assert "users ||--o{ comments : author" in graph_string
-
-    assert "CHAR(32) author FK" in graph_string
-    assert 'CHAR(32) post FK "nullable"' in graph_string
-    assert "DATETIME created" in graph_string
+    mermaid_assert(graph_string)
diff --git a/tests/transformers/test_mermaid.py b/tests/transformers/test_mermaid.py
index cd176e1..4a5be2a 100644
--- a/tests/transformers/test_mermaid.py
+++ b/tests/transformers/test_mermaid.py
@@ -1,19 +1,9 @@
 from paracelsus.transformers.mermaid import Mermaid
 
+from ..utils import mermaid_assert
+
 
 def test_mermaid(metaclass):
     mermaid = Mermaid(metaclass=metaclass)
     graph_string = str(mermaid)
-
-    assert "users {" in graph_string
-    assert "posts {" in graph_string
-    assert "comments {" in graph_string
-
-    assert "users ||--o{ posts : author" in graph_string
-    assert "posts ||--o{ comments : post" in graph_string
-    assert "users ||--o{ comments : author" in graph_string
-
-    assert "CHAR(32) author FK" in graph_string
-    assert 'CHAR(32) post FK "nullable"' in graph_string
-    assert 'BOOLEAN live "True if post is published,nullable"' in graph_string
-    assert "DATETIME created" in graph_string
+    mermaid_assert(graph_string)
diff --git a/tests/utils.py b/tests/utils.py
new file mode 100644
index 0000000..4aa3782
--- /dev/null
+++ b/tests/utils.py
@@ -0,0 +1,13 @@
+def mermaid_assert(output: str) -> None:
+    assert "users {" in output
+    assert "posts {" in output
+    assert "comments {" in output
+
+    assert "users ||--o{ posts : author" in output
+    assert "posts ||--o{ comments : post" in output
+    assert "users ||--o{ comments : author" in output
+
+    assert "CHAR(32) author FK" in output
+    assert 'CHAR(32) post FK "nullable"' in output
+    assert 'BOOLEAN live "True if post is published,nullable"' in output
+    assert "DATETIME created" in output