Add tests for new Figure layout argument.

Author: QuLogic

lib/matplotlib/figure.py

@@ -2241,7 +2241,7 @@ def __init__(self,
                 tight_layout = True
                 constrained_layout = False
             else:
-                raise ValueError(f"Invalid value for 'layout': {layout!r}")
+                _api.check_in_list(['constrained', 'tight'], layout=layout)
 
         self.callbacks = cbook.CallbackRegistry()
         # Callbacks traditionally associated with the canvas (and exposed with

lib/matplotlib/tests/test_figure.py

@@ -501,13 +501,44 @@ def test_figure_repr():
     assert repr(fig) == "<Figure size 100x200 with 0 Axes>"
 
 
-def test_warn_cl_plus_tl():
+def test_valid_layouts():
+    fig = Figure(layout=None)
+    assert not fig.get_tight_layout()
+    assert not fig.get_constrained_layout()
+
+    fig = Figure(layout='tight')
+    assert fig.get_tight_layout()
+    assert not fig.get_constrained_layout()
+
+    fig = Figure(layout='constrained')
+    assert not fig.get_tight_layout()
+    assert fig.get_constrained_layout()
+
+
+def test_invalid_layouts():
     fig, ax = plt.subplots(constrained_layout=True)
     with pytest.warns(UserWarning):
         # this should warn,
         fig.subplots_adjust(top=0.8)
     assert not(fig.get_constrained_layout())
 
+    # Using layout + (tight|constrained)_layout warns, but the former takes
+    # precedence.
+    with pytest.warns(UserWarning, match="Figure parameters 'layout' and "
+                      "'tight_layout' cannot"):
+        fig = Figure(layout='tight', tight_layout=False)
+    assert fig.get_tight_layout()
+    assert not fig.get_constrained_layout()
+    with pytest.warns(UserWarning, match="Figure parameters 'layout' and "
+                      "'constrained_layout' cannot"):
+        fig = Figure(layout='constrained', constrained_layout=False)
+    assert not fig.get_tight_layout()
+    assert fig.get_constrained_layout()
+
+    with pytest.raises(ValueError,
+                       match="'foobar' is not a valid value for layout"):
+        Figure(layout='foobar')
+
 
 @check_figures_equal(extensions=["png", "pdf"])
 def test_add_artist(fig_test, fig_ref):