Convert graphics testing conveniences to PyTest

[trexfeathers]

Make sure you squash merge!

(the commits are a bit of a mess)

• README
• __init__
• idiff
• recreate_imagerepo

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.74%. Comparing base (fa86a4f) to head (db0da75).
Report is 11 commits behind head on FEATURE_pytest_conversion.

Additional details and impacted files

@@                    Coverage Diff                     @@
##           FEATURE_pytest_conversion    #5832   +/-   ##
==========================================================
  Coverage                      89.74%   89.74%           
==========================================================
  Files                             92       92           
  Lines                          22940    22940           
  Branches                        5462     5462           
==========================================================
  Hits                           20588    20588           
  Misses                          1620     1620           
  Partials                         732      732           

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[trexfeathers]

The tests below (from these changes) demonstrate that check_graphics_caller() can support PyTest style tests. If you click the below you will note the full set of ✔ checks. I will revert this demo so that test_plot.py can be converted in a dedicated PR.

iris/lib/iris/tests/test_plot.py

Lines 242 to 302 in 68f81ac

	@tests.skip_data
	@tests.skip_plot
	class Test1dScatter:
	@pytest.fixture(autouse=True)
	def set_draw_method(self):
	self.draw_method = iplt.scatter
	@pytest.fixture(autouse=True)
	def setup(self, check_graphic_caller):
	self.cube = iris.load_cube(
	tests.get_data_path(("NAME", "NAMEIII_trajectory.txt")),
	"Temperature",
	)
	self.check_graphic = check_graphic_caller
	def test_coord_coord(self):
	x = self.cube.coord("longitude")
	y = self.cube.coord("altitude")
	c = self.cube.data
	self.draw_method(x, y, c=c, edgecolor="none")
	self.check_graphic()
	def test_coord_coord_map(self):
	x = self.cube.coord("longitude")
	y = self.cube.coord("latitude")
	c = self.cube.data
	self.draw_method(x, y, c=c, edgecolor="none")
	plt.gca().coastlines("110m")
	self.check_graphic()
	def test_coord_cube(self):
	x = self.cube.coord("latitude")
	y = self.cube
	c = self.cube.coord("Travel Time").points
	self.draw_method(x, y, c=c, edgecolor="none")
	self.check_graphic()
	def test_cube_coord(self):
	x = self.cube
	y = self.cube.coord("altitude")
	c = self.cube.coord("Travel Time").points
	self.draw_method(x, y, c=c, edgecolor="none")
	self.check_graphic()
	def test_cube_cube(self):
	x = iris.load_cube(
	tests.get_data_path(("NAME", "NAMEIII_trajectory.txt")),
	"Rel Humidity",
	)
	y = self.cube
	c = self.cube.coord("Travel Time").points
	self.draw_method(x, y, c=c, edgecolor="none")
	self.check_graphic()
	@tests.skip_data
	@tests.skip_plot
	class Test1dQuickplotScatter(Test1dScatter):
	@pytest.fixture(autouse=True)
	def set_draw_method(self):
	self.draw_method = qplt.scatter

[ESadek-MO]

Thanks @trexfeathers, LGTM.

Docstrings good and code clean :)