Ensure that no tests are attempted if numpy or rpy2 are not present.

This prevents both importing of the extension itself and running of
the test suite.

IPython/testing/iptest.py

@@ -143,16 +143,17 b' have = {}'
 
 have['curses'] = test_for('_curses')
 have['matplotlib'] = test_for('matplotlib')
+have['numpy'] = test_for('numpy')
 have['pexpect'] = test_for('IPython.external.pexpect')
 have['pymongo'] = test_for('pymongo')
 have['pygments'] = test_for('pygments')
-have['wx'] = test_for('wx')
-have['wx.aui'] = test_for('wx.aui')
 have['qt'] = test_for('IPython.external.qt')
+have['rpy2'] = test_for('rpy2')
 have['sqlite3'] = test_for('sqlite3')
 have['cython'] = test_for('Cython')
-
 have['tornado'] = test_for('tornado.version_info', (2,1,0), callback=None)
+have['wx'] = test_for('wx')
+have['wx.aui'] = test_for('wx.aui')
 
 if os.name == 'nt':
     min_zmq = (2,1,7)
@@ -275,6 +276,10 b' def make_exclude():'
     if not have['tornado']:
         exclusions.append(ipjoin('frontend', 'html'))
 
+    if not have['rpy2'] or not have['numpy']:
+        exclusions.append(ipjoin('extensions', 'rmagic'))
+        exclusions.append(ipjoin('extensions', 'tests', 'test_rmagic'))
+
     # This is needed for the reg-exp to match on win32 in the ipdoctest plugin.
     if sys.platform == 'win32':
         exclusions = [s.replace('\\','\\\\') for s in exclusions]