Sketch of how Iris gallery tests might work with `pytest-mpl`. I guess we'd need multiple classes to handle examples with different numbers of figures (at time of writing all examples have one, two or four figures). See also https://stackoverflow.com/questions/72659961/generate-multiple-tests-based-on-a-functions-output.

test_multiplots.py

import warnings

import matplotlib.pyplot as plt
import pytest


def my_plots():
    plt.figure()
    plt.plot([0, 1])
    plt.show()
    
    plt.figure()
    plt.plot([0, 2])
    warnings.warn("bad things may happen")
    plt.show()
    
    
def my_other_plots():
    plt.plot([1, 0])
    plt.show()
    
    plt.figure()
    plt.plot([-3, 5])
    plt.show()
    
    
@pytest.fixture(scope="class")
def image_setup_teardown(plot_func):
    plt.close("all")
    yield
    plt.close("all")
    
 
@pytest.mark.mpl_image_compare   
def check_fig(self, fig_index, get_figures):
    return get_figures[fig_index]
    

@pytest.mark.parametrize("plot_func", [my_plots, my_other_plots], scope="class")
class TestPlots:
    @pytest.fixture(scope="class")
    def get_figures(self, plot_func, image_setup_teardown):
        figs = []
        def append_fig():
            figs.append(plt.gcf())
        
        with pytest.MonkeyPatch.context() as mp:
            mp.setattr(plt, "show", append_fig)
            plot_func()
            
        return figs
    
    @pytest.mark.filterwarnings("error")    
    def test_num_figs(self, get_figures):
        assert len(get_figures) == 2

    test_my_plots = pytest.mark.parametrize("fig_index", [0, 1])(check_fig)