Also call graphics.show() in doctest mode

src/sage/plot/graphics.py

@@ -1828,6 +1828,10 @@ def show(self, filename=None, linkmode=False, **kwds):
         specify ``ticks`` manually, this safety measure can be defeated::
 
             sage: list_plot_loglog([(1,2),(2,3)], plotjoined=True, ticks=[[1],[1]])
+            doctest:...: UserWarning: The x-axis contains fewer than 2 ticks; 
+            the logarithmic scale of the plot may not be apparent to the reader.
+            doctest:...: UserWarning: The y-axis contains fewer than 2 ticks; 
+            the logarithmic scale of the plot may not be apparent to the reader.
             Graphics object consisting of 1 graphics primitive
 
         This one works, since the horizontal axis is automatically expanded
@@ -2318,7 +2322,9 @@ def matplotlib(self, filename=None,
         ``typeset`` must not be set to an arbitrary string::
 
             sage: plot(x, typeset='garbage')
-            Graphics object consisting of 1 graphics primitive
+            doctest:...: FormatterWarning: Exception in text/plain formatter: 
+            typeset must be set to one of 'default', 'latex', or 'type1'; got 'garbage'.
+            None
 
         We verify that numerical options are changed to float before saving (:trac:`14741`).
         By default, Sage 5.10 changes float objects to the `RealLiteral` type.

src/sage/plot/plot3d/base.pyx

@@ -1882,7 +1882,7 @@ cdef class PrimitiveObject(Graphics3d):
 
             sage: G = dodecahedron(color='red')
             sage: G.texture_set()
-            {Texture(texture540, red, ff0000)}
+            {Texture(texture..., red, ff0000)}
         """
         return set([self.texture])
 

src/sage/repl/display/formatter.py

@@ -236,6 +236,51 @@ def __call__(self, obj):
         return stream.getvalue()
 
 
+class SageDoctestTextFormatter(SagePlainTextFormatter):
+
+    @warn_format_error
+    def __call__(self, obj):
+        """
+        Display ``obj``.
+
+        For doctests, we both 
+
+        * Print the textual representation. This makes it clear in the
+          documentation that the command returns graphics.
+
+        * Run ``show()`` on graphics objects, to test that it
+          correctly generates graphics. Note that, in
+          ``DOCTEST_MODE``, the ``show()`` method will save graphics
+          to temporary files but not launch a viewer.
+
+        INPUT:
+
+        - ``obj`` -- anything.
+
+        OUTPUT:
+
+        String. The plain text representation.
+
+        EXAMPLES::
+
+            sage: class FooGraphics(SageObject):
+            ....:     def _graphics_(self):
+            ....:         print('showing graphics') 
+            ....:         return True
+            ....:     def _repr_(self):
+            ....:         return 'Textual representation'
+            sage: from sage.repl.display.formatter import SageDoctestTextFormatter
+            sage: fmt = SageDoctestTextFormatter()
+            sage: fmt(FooGraphics())
+            showing graphics
+            'Textual representation'
+        """
+        from sage.structure.sage_object import SageObject
+        if isinstance(obj, SageObject) and hasattr(obj, '_graphics_'):
+            obj._graphics_()      # ignore whether there actually is graphics
+        return super(SageDoctestTextFormatter, self).__call__(obj)
+
+
 class SageConsoleTextFormatter(SagePlainTextFormatter):
 
     @warn_format_error
@@ -266,6 +311,8 @@ def __call__(self, obj):
             ....:     def _graphics_(self):
             ....:         print('showing graphics') 
             ....:         return True
+            ....:     def _repr_(self):
+            ....:         return 'Textual representation'
             sage: from sage.repl.display.formatter import SageConsoleTextFormatter
             sage: fmt = SageConsoleTextFormatter()
             sage: fmt(FooGraphics())

src/sage/repl/display/python_hook.py

@@ -20,7 +20,7 @@
 import __builtin__
 
 
-from sage.repl.display.formatter import SagePlainTextFormatter
+from sage.repl.display.formatter import SageDoctestTextFormatter
 
 
 class DoctestDisplayHook(object):
@@ -38,7 +38,7 @@ def __init__(self):
             sage: print(set([1, 2, 3]))   # Plain Python output
             set([1, 2, 3])
         """
-        self.formatter = SagePlainTextFormatter()
+        self.formatter = SageDoctestTextFormatter()
 
     def __call__(self, obj):
         """