Test qcircuit with actual PDF output (#7665)

- Change `test_qcircuit_pdf` to compile PDF file
- Install LaTeX and latexmk for the CI jobs

Prerequisite for tests in #7354

Author: pavoljuhas

.github/workflows/ci.yml

@@ -99,6 +99,10 @@ jobs:
         with:
           python-version: '3.11'
           architecture: 'x64'
+      - name: Install system packages
+        run: |
+          sudo apt-get update
+          sudo apt-get install latexmk texlive-latex-base texlive-latex-extra
       - name: Install changed files test dependencies
         run: dev_tools/conf/pip-install-minimal-for-pytest-changed-files.sh
       - name: Changed files test
@@ -203,6 +207,10 @@ jobs:
           cache-dependency-path: |
             **/requirements.txt
             dev_tools/requirements/**/*.txt
+      - name: Install system packages
+        run: |
+          sudo apt-get update
+          sudo apt-get install latexmk texlive-latex-base texlive-latex-extra
       - name: Install requirements
         run: |
           pip install --upgrade setuptools wheel
@@ -263,6 +271,10 @@ jobs:
           cache-dependency-path: |
             **/requirements.txt
             dev_tools/requirements/**/*.txt
+      - name: Install system packages
+        run: |
+          sudo apt-get update
+          sudo apt-get install latexmk texlive-latex-base texlive-latex-extra
       - name: Install requirements
         run: |
           pip install --upgrade setuptools wheel

cirq-core/cirq/contrib/qcircuit/qcircuit_pdf_test.py

@@ -14,18 +14,15 @@
 
 from __future__ import annotations
 
-from unittest import mock
-
-import pylatex
+import pathlib
 
 import cirq
 import cirq.contrib.qcircuit.qcircuit_pdf as qcircuit_pdf
 
 
-@mock.patch.object(pylatex.Document, "generate_pdf")
-def test_qcircuit_pdf(mock_generate_pdf) -> None:
+def test_qcircuit_pdf(tmp_path: pathlib.Path) -> None:
     circuit = cirq.Circuit(cirq.X(cirq.q(0)), cirq.CZ(cirq.q(0), cirq.q(1)))
-    qcircuit_pdf.circuit_to_pdf_using_qcircuit_via_tex(circuit, "/tmp/test_file")
-    mock_generate_pdf.assert_called_once_with(
-        "/tmp/test_file", compiler="latexmk", compiler_args=["-pdfps"]
-    )
+    qcircuit_pdf.circuit_to_pdf_using_qcircuit_via_tex(circuit, f"{tmp_path}/test_file")
+    assert (tmp_path / "test_file.pdf").is_file()
+    assert not (tmp_path / "test_file.dvi").exists()
+    assert not (tmp_path / "test_file.ps").exists()