Refactor: Use pytest parametrize for format tests

Use pytest.mark.parametrize to reduce code duplication in format tests.
Remove PGF test as LaTeX backend is not available in CI environment.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: ianhi

tests/test_download.py

@@ -9,12 +9,19 @@
 import pytest
 
 
-def test_send_save_buffer_respects_format():
+@pytest.mark.parametrize(
+    "format_name,signature_check",
+    [
+        ("png", lambda buf: len(buf) > 0 and buf[:8] == b'\x89PNG\r\n\x1a\n'),
+        ("pdf", lambda buf: buf[:4] == b'%PDF'),
+        ("svg", lambda buf: b'<?xml' in buf or b'<svg' in buf),
+    ]
+)
+def test_send_save_buffer_respects_format(format_name, signature_check):
     """Test that _send_save_buffer respects savefig.format rcParam."""
     matplotlib.use('module://ipympl.backend_nbagg')
 
-    # Test PNG format (default)
-    plt.rcParams['savefig.format'] = 'png'
+    plt.rcParams['savefig.format'] = format_name
     fig, ax = plt.subplots()
     ax.plot([1, 2, 3], [1, 4, 2])
 
@@ -30,61 +37,12 @@ def test_send_save_buffer_respects_format():
     # Check message format
     msg_data = json.loads(call_args[0][0]['data'])
     assert msg_data['type'] == 'save'
-    assert msg_data['format'] == 'png'
+    assert msg_data['format'] == format_name
 
-    # Check buffer is not empty
+    # Check buffer signature
     buffers = call_args[1]['buffers']
     assert len(buffers) == 1
-    assert len(buffers[0]) > 0
-
-    plt.close(fig)
-
-
-def test_send_save_buffer_respects_pdf_format():
-    """Test that _send_save_buffer respects PDF format."""
-    matplotlib.use('module://ipympl.backend_nbagg')
-
-    plt.rcParams['savefig.format'] = 'pdf'
-    fig, ax = plt.subplots()
-    ax.plot([1, 2, 3], [1, 4, 2])
-
-    canvas = fig.canvas
-    canvas.send = MagicMock()
-
-    canvas._send_save_buffer()
-
-    call_args = canvas.send.call_args
-    msg_data = json.loads(call_args[0][0]['data'])
-    assert msg_data['format'] == 'pdf'
-
-    # Verify buffer starts with PDF signature
-    buffers = call_args[1]['buffers']
-    assert buffers[0][:4] == b'%PDF'
-
-    plt.close(fig)
-
-
-def test_send_save_buffer_respects_svg_format():
-    """Test that _send_save_buffer respects SVG format."""
-    matplotlib.use('module://ipympl.backend_nbagg')
-
-    plt.rcParams['savefig.format'] = 'svg'
-    fig, ax = plt.subplots()
-    ax.plot([1, 2, 3], [1, 4, 2])
-
-    canvas = fig.canvas
-    canvas.send = MagicMock()
-
-    canvas._send_save_buffer()
-
-    call_args = canvas.send.call_args
-    msg_data = json.loads(call_args[0][0]['data'])
-    assert msg_data['format'] == 'svg'
-
-    # Verify buffer contains SVG content
-    buffers = call_args[1]['buffers']
-    buffer_str = buffers[0].decode('utf-8')
-    assert '<?xml' in buffer_str or '<svg' in buffer_str
+    assert signature_check(buffers[0])
 
     plt.close(fig)
 
@@ -189,30 +147,3 @@ def test_send_save_buffer_respects_transparent():
     assert len(buffers[0]) > 0
 
     plt.close(fig)
-
-
-def test_send_save_buffer_with_pgf_format():
-    """Test that _send_save_buffer works with PGF format."""
-    matplotlib.use('module://ipympl.backend_nbagg')
-
-    # Test with PGF format (LaTeX graphics format)
-    plt.rcParams['savefig.format'] = 'pgf'
-
-    fig, ax = plt.subplots()
-    ax.plot([1, 2, 3], [1, 4, 2])
-
-    canvas = fig.canvas
-    canvas.send = MagicMock()
-
-    # Should work without warnings
-    canvas._send_save_buffer()
-
-    # Should send the buffer with format='pgf'
-    assert canvas.send.called
-    call_args = canvas.send.call_args
-    assert 'data' in call_args[0][0]
-    import json
-    msg_data = json.loads(call_args[0][0]['data'])
-    assert msg_data['format'] == 'pgf'
-
-    plt.close(fig)