ci: add tests with LaTeX

Add dedicated GitHub Actions workflow (ci_latex.yml) for testing
LaTeX-dependent matplotlib styles:
- CMSTex, ROOTTex (CMS experiment)
- DUNETex, DUNETex1 (DUNE experiment)
- ATLASTex (ATLAS experiment)
- LHCbTex1, LHCbTex2 (LHCb experiment)

The workflow:
- Installs full TeXLive distribution with required packages
- Runs on PRs that modify style files or LaTeX tests
- Runs weekly (Monday at 0:00 UTC) to catch regressions
- Can be triggered manually via workflow_dispatch

Also adds comprehensive test file (test_styles_latex.py) with
baseline images for all LaTeX styles.

Closes #603

Author: andrzejnovak

.github/workflows/ci_latex.yml

@@ -0,0 +1,87 @@
+# GitHub Actions workflow for testing LaTeX-dependent styles
+#
+# This workflow tests matplotlib styles that require LaTeX to be installed:
+# - CMSTex, ROOTTex (CMS experiment)
+# - DUNETex, DUNETex1 (DUNE experiment)
+# - ATLASTex (ATLAS experiment)
+# - LHCbTex1, LHCbTex2 (LHCb experiment)
+#
+# These tests are separated from the main CI workflow because:
+# 1. LaTeX installation adds ~500MB and several minutes to CI time
+# 2. LaTeX rendering can be environment-dependent
+# 3. Most PRs don't affect LaTeX-dependent features
+#
+# The workflow runs:
+# - On pull requests that modify style files or LaTeX tests
+# - Weekly (every Monday) to catch regressions
+# - Manually via workflow_dispatch
+
+name: CI LaTeX
+
+on:
+  workflow_dispatch:
+  pull_request:
+    paths:
+      - 'src/mplhep/styles/**'
+      - 'tests/test_styles_latex.py'
+      - 'tests/test_dune.py'
+      - '.github/workflows/ci_latex.yml'
+  # Run weekly on Monday at 0:00 UTC
+  schedule:
+    - cron: '0 0 * * 1'
+
+jobs:
+
+  test-latex:
+    name: "LaTeX Tests • Python ${{ matrix.python-version }}"
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ['3.12']
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup TeXLive
+        uses: xu-cheng/texlive-action@v3
+
+      - name: Setup uv
+        uses: astral-sh/setup-uv@v5
+        with:
+          version: 'latest'
+          python-version: ${{ matrix.python-version }}
+          enable-cache: true
+          cache-dependency-glob: '**/pyproject.toml'
+
+      - name: Install core fonts
+        run: |
+          echo ttf-mscorefonts-installer msttcorefonts/accepted-mscorefonts-eula select true | sudo debconf-set-selections
+          sudo apt-get install ttf-mscorefonts-installer
+
+      - name: Install package
+        run: |
+          uv pip install -e '.[all]'
+          uv pip install pytest-github-actions-annotate-failures
+          uv pip install pytest-xdist
+          uv pip list
+
+      - name: Test LaTeX styles with pytest
+        run: |
+          python -m pytest tests/test_styles_latex.py -r sa --mpl --mpl-results-path=pytest_results_latex -n 4
+
+      - name: Test DUNE LaTeX styles with pytest
+        run: |
+          python -m pytest tests/test_dune.py::test_style_dunetex -r sa --mpl --mpl-results-path=pytest_results_dune_tex
+          python -m pytest tests/test_dune.py::test_style_dunetex1 -r sa --mpl --mpl-results-path=pytest_results_dune_tex
+          python -m pytest tests/test_dune.py::test_dune_style_string_aliases -r sa --mpl --mpl-results-path=pytest_results_dune_tex
+
+      - name: Upload pytest test results
+        uses: actions/upload-artifact@v4
+        if: failure()
+        with:
+          name: pytest_results_latex-${{ matrix.python-version }}
+          retention-days: 7
+          path: |
+            pytest_results_latex
+            pytest_results_dune_tex

tests/baseline/test_style_atlastex.png

@@ -1,3 +1,6 @@
+import shutil
+import subprocess
+
 import matplotlib.pyplot as plt
 import pytest
 
@@ -10,6 +13,42 @@ def pytest_configure(config):
         # Running with xdist, disable pytest-asyncio
         config.pluginmanager.set_blocked("pytest_asyncio")
 
+    # Register custom markers
+    config.addinivalue_line(
+        "markers", "latex: tests that require LaTeX to be installed"
+    )
+
+
+def _has_latex():
+    """Check if LaTeX is available on the system."""
+    if not shutil.which("latex"):
+        return False
+    try:
+        subprocess.run(
+            ["latex", "--version"],
+            check=True,
+            capture_output=True,
+            timeout=5,
+        )
+        return True
+    except (
+        subprocess.CalledProcessError,
+        subprocess.TimeoutExpired,
+        FileNotFoundError,
+    ):
+        return False
+
+
+def pytest_collection_modifyitems(config, items):  # noqa: ARG001
+    """Skip LaTeX tests if LaTeX is not installed."""
+    if _has_latex():
+        return
+
+    skip_latex = pytest.mark.skip(reason="LaTeX not installed")
+    for item in items:
+        if "latex" in item.keywords:
+            item.add_marker(skip_latex)
+
 
 @pytest.fixture(autouse=True)
 def clear_mplhep_rcparams():

tests/baseline/test_style_cmstex.png

@@ -42,10 +42,8 @@ def test_dune_style_str_alias(fig_test, fig_ref):
     fig_test.subplots()
 
 
+@pytest.mark.latex
 @pytest.mark.skipif(sys.platform != "linux", reason="Linux only")
-@pytest.mark.skipif(
-    os.environ.get("GITHUB_ACTIONS") == "true", reason="Fails in GitHub Actions"
-)
 @pytest.mark.mpl_image_compare(style="default", remove_text=False)
 def test_style_dunetex():
     plt.rcParams.update(plt.rcParamsDefault)
@@ -58,10 +56,8 @@ def test_style_dunetex():
     return fig
 
 
+@pytest.mark.latex
 @pytest.mark.skipif(sys.platform != "linux", reason="Linux only")
-@pytest.mark.skipif(
-    os.environ.get("GITHUB_ACTIONS") == "true", reason="Fails in GitHub Actions"
-)
 @pytest.mark.mpl_image_compare(style="default", remove_text=False)
 def test_style_dunetex1():
     plt.rcParams.update(plt.rcParamsDefault)
@@ -84,18 +80,12 @@ def test_style_dunetex1():
         pytest.param(
             mh.style.DUNETex,
             "DUNETex",
-            marks=pytest.mark.skipif(
-                os.environ.get("GITHUB_ACTIONS") == "true",
-                reason="Fails in GitHub Actions",
-            ),
+            marks=pytest.mark.latex,
         ),
         pytest.param(
             mh.style.DUNETex1,
             "DUNETex1",
-            marks=pytest.mark.skipif(
-                os.environ.get("GITHUB_ACTIONS") == "true",
-                reason="Fails in GitHub Actions",
-            ),
+            marks=pytest.mark.latex,
         ),
     ],
     ids=["DUNE", "DUNE1", "DUNETex", "DUNETex1"],

tests/baseline/test_style_lhcbtex1.png

@@ -0,0 +1,149 @@
+from __future__ import annotations
+
+import os
+import sys
+
+import matplotlib.pyplot as plt
+import pytest
+from matplotlib.testing.decorators import check_figures_equal
+
+os.environ["RUNNING_PYTEST"] = "true"
+
+import mplhep as mh
+
+"""
+Tests for LaTeX-dependent styles (CMSTex, DUNETex, ATLASTex, LHCbTex, etc.)
+
+To test run:
+pytest tests/test_styles_latex.py --mpl
+
+When adding new tests, run:
+pytest tests/test_styles_latex.py --mpl-generate-path=tests/baseline
+"""
+
+plt.switch_backend("Agg")
+
+pytestmark = [
+    pytest.mark.latex,
+    pytest.mark.skipif(sys.platform != "linux", reason="Linux only"),
+]
+
+
+@pytest.mark.mpl_image_compare(style="default", remove_text=False)
+def test_style_cmstex():
+    plt.rcParams.update(plt.rcParamsDefault)
+
+    plt.style.use(mh.style.CMSTex)
+    fig, ax = plt.subplots()
+    mh.cms.label("Preliminary")
+
+    plt.rcParams.update(plt.rcParamsDefault)
+    return fig
+
+
+@pytest.mark.mpl_image_compare(style="default", remove_text=False)
+def test_style_roottex():
+    plt.rcParams.update(plt.rcParamsDefault)
+
+    plt.style.use(mh.style.ROOTTex)
+    fig, ax = plt.subplots()
+    ax.set_xlabel(r"$p_T$ [GeV]")
+    ax.set_ylabel(r"Events / 10 GeV")
+
+    plt.rcParams.update(plt.rcParamsDefault)
+    return fig
+
+
+@pytest.mark.mpl_image_compare(style="default", remove_text=False)
+def test_style_dunetex():
+    plt.rcParams.update(plt.rcParamsDefault)
+
+    plt.style.use(mh.style.DUNETex)
+    fig, ax = plt.subplots()
+    mh.dune.label(text="Preliminary")
+
+    plt.rcParams.update(plt.rcParamsDefault)
+    return fig
+
+
+@pytest.mark.mpl_image_compare(style="default", remove_text=False)
+def test_style_dunetex1():
+    plt.rcParams.update(plt.rcParamsDefault)
+
+    plt.style.use(mh.style.DUNETex1)
+    fig, ax = plt.subplots()
+    mh.dune.label(text="Preliminary")
+
+    plt.rcParams.update(plt.rcParamsDefault)
+    return fig
+
+
+@pytest.mark.mpl_image_compare(style="default", remove_text=False)
+def test_style_atlastex():
+    plt.rcParams.update(plt.rcParamsDefault)
+
+    plt.style.use(mh.style.ATLASTex)
+    fig, ax = plt.subplots()
+    mh.atlas.label(text="Preliminary")
+
+    plt.rcParams.update(plt.rcParamsDefault)
+    return fig
+
+
+@pytest.mark.mpl_image_compare(style="default", remove_text=False)
+def test_style_lhcbtex1():
+    plt.rcParams.update(plt.rcParamsDefault)
+
+    plt.style.use([mh.style.LHCbTex1, {"figure.autolayout": False}])
+    fig, ax = plt.subplots()
+    mh.lhcb.label("Preliminary")
+
+    plt.rcParams.update(plt.rcParamsDefault)
+    return fig
+
+
+@pytest.mark.mpl_image_compare(style="default", remove_text=False)
+def test_style_lhcbtex2():
+    plt.rcParams.update(plt.rcParamsDefault)
+
+    plt.style.use([mh.style.LHCbTex2, {"figure.autolayout": False}])
+    fig, ax = plt.subplots()
+    mh.lhcb.label("Preliminary")
+
+    plt.rcParams.update(plt.rcParamsDefault)
+    return fig
+
+
+@check_figures_equal(extensions=["pdf"])
+@pytest.mark.parametrize(
+    ("mplhep_style", "str_alias"),
+    [
+        (mh.style.CMSTex, "CMSTex"),
+        (mh.style.ROOTTex, "ROOTTex"),
+        (mh.style.DUNETex, "DUNETex"),
+        (mh.style.DUNETex1, "DUNETex1"),
+        (mh.style.ATLASTex, "ATLASTex"),
+        (mh.style.LHCbTex1, "LHCbTex1"),
+        (mh.style.LHCbTex2, "LHCbTex2"),
+    ],
+    ids=[
+        "CMSTex",
+        "ROOTTex",
+        "DUNETex",
+        "DUNETex1",
+        "ATLASTex",
+        "LHCbTex1",
+        "LHCbTex2",
+    ],
+)
+def test_latex_style_str_alias(fig_test, fig_ref, mplhep_style, str_alias):
+    """Test that string aliases work for all LaTeX style variants."""
+    plt.rcParams.update(plt.rcParamsDefault)
+
+    mh.rcParams.clear()
+    plt.style.use(mplhep_style)
+    fig_ref.subplots()
+
+    mh.rcParams.clear()
+    mh.style.use(str_alias)
+    fig_test.subplots()