Better Diagnostic for LaTeX errors

tests/test_utils_compile.py

@@ -27,9 +27,26 @@ class CompileToPdfTests(unittest.TestCase):
                 utils.compile_to_pdf("broken", output)
 
             self.assertEqual(output.read_bytes(), b"partial")
-            self.assertIn("Warning: LaTeX compilation failed", console.getvalue())
+            self.assertIn("Warning: LaTeX compilation reported errors", console.getvalue())
+            self.assertIn("a PDF was generated", console.getvalue())
             self.assertIn("missing \\item", console.getvalue())
 
+    def test_says_no_pdf_was_generated_when_latex_fails(self):
+        with tempfile.TemporaryDirectory() as temporary:
+            output = Path(temporary) / "result.pdf"
+            result = subprocess.CompletedProcess(
+                args=[], returncode=1, stdout="! Undefined control sequence.\n"
+            )
+
+            console = io.StringIO()
+            with patch.object(utils.subprocess, "run", return_value=result), \
+                    contextlib.redirect_stdout(console):
+                utils.compile_to_pdf("broken", output)
+
+            self.assertFalse(output.exists())
+            self.assertIn("no PDF was generated", console.getvalue())
+            self.assertIn("Undefined control sequence", console.getvalue())
+
     def test_warns_when_no_pdf_is_produced(self):
         with tempfile.TemporaryDirectory() as temporary:
             output = Path(temporary) / "result.pdf"