Mechanism for testing terminal interact loop in-process.

While this is complex, I much prefer it to starting a separate process
and piping commands in.

IPython/terminal/tests/test_interactivshell.py

@@ -17,12 +17,68 b' Authors'
 #-----------------------------------------------------------------------------
 # stdlib
 import sys
+import types
 import unittest
 
+from IPython.core.inputtransformer import InputTransformer
 from IPython.testing.decorators import skipif
 from IPython.utils import py3compat
 from IPython.testing import tools as tt
 
+# Decorator for interaction loop tests -----------------------------------------
+
+class mock_input_helper(object):
+    """Machinery for tests of the main interact loop.
+
+    Used by the mock_input decorator.
+    """
+    def __init__(self, testgen):
+        self.testgen = testgen
+        self.exception = None
+        self.ip = get_ipython()
+
+    def __enter__(self):
+        self.orig_raw_input = self.ip.raw_input
+        self.ip.raw_input = self.fake_input
+        return self
+
+    def __exit__(self, etype, value, tb):
+        self.ip.raw_input = self.orig_raw_input
+
+    def fake_input(self, prompt):
+        try:
+            return next(self.testgen)
+        except StopIteration:
+            self.ip.exit_now = True
+            return u''
+        except:
+            self.exception = sys.exc_info()
+            self.ip.exit_now = True
+            return u''
+
+def mock_input(testfunc):
+    """Decorator for tests of the main interact loop.
+
+    Write the test as a generator, yield-ing the input strings, which IPython
+    will see as if they were typed in at the prompt.
+    """
+    def test_method(self):
+        testgen = testfunc(self)
+        with mock_input_helper(testgen) as mih:
+            mih.ip.interact(display_banner=False)
+
+        if mih.exception is not None:
+            # Re-raise captured exception
+            etype, value, tb = mih.exception
+            import traceback
+            traceback.print_tb(tb, file=sys.stdout)
+            del tb  # Avoid reference loop
+            raise value
+
+    return test_method
+
+# Test classes -----------------------------------------------------------------
+
 class InteractiveShellTestCase(unittest.TestCase):
     def rl_hist_entries(self, rl, n):
         """Get last n readline history entries as a list"""
@@ -171,6 +227,42 b' class InteractiveShellTestCase(unittest.TestCase):'
         expected = [ py3compat.unicode_to_str(e, enc) for e in expected ]
         self.assertEqual(hist, expected)
     
+    @mock_input
+    def test_inputtransformer_syntaxerror(self):
+        ip = get_ipython()
+        transformer = SyntaxErrorTransformer()
+        ip.input_splitter.python_line_transforms.append(transformer)
+        ip.input_transformer_manager.python_line_transforms.append(transformer)
+
+        try:
+            #raise Exception
+            with tt.AssertPrints('4', suppress=False):
+                yield u'print(2*2)'
+
+            with tt.AssertPrints('SyntaxError: input contains', suppress=False):
+                yield u'print(2345) # syntaxerror'
+
+            with tt.AssertPrints('16', suppress=False):
+                yield u'print(4*4)'
+
+        finally:
+            ip.input_splitter.python_line_transforms.remove(transformer)
+            ip.input_transformer_manager.python_line_transforms.remove(transformer)
+
+
+class SyntaxErrorTransformer(InputTransformer):
+    def push(self, line):
+        pos = line.find('syntaxerror')
+        if pos >= 0:
+            e = SyntaxError('input contains "syntaxerror"')
+            e.text = line
+            e.offset = pos + 1
+            raise e
+        return line
+
+    def reset(self):
+        pass
+
 class TerminalMagicsTestCase(unittest.TestCase):
     def test_paste_magics_message(self):
         """Test that an IndentationError while using paste magics doesn't

IPython/testing/tools.py

@@ -173,7 +173,7 b' def get_ipython_cmd(as_string=False):'
 
     return ipython_cmd
 
-def ipexec(fname, options=None, pipe=False):
+def ipexec(fname, options=None):
     """Utility to call 'ipython filename'.
 
     Starts IPython with a minimal and safe configuration to make startup as fast
@@ -189,9 +189,6 b' def ipexec(fname, options=None, pipe=False):'
     options : optional, list
       Extra command-line flags to be passed to IPython.
 
-    pipe : optional, boolean
-      Pipe fname into IPython as stdin instead of calling it as external file
-
     Returns
     -------
     (stdout, stderr) of ipython subprocess.
@@ -211,10 +208,6 b' def ipexec(fname, options=None, pipe=False):'
     ipython_cmd = get_ipython_cmd()
     # Absolute path for filename
     full_fname = os.path.join(test_dir, fname)
-    if pipe:
-        full_cmd = ipython_cmd + cmdargs
-        p = Popen(full_cmd, stdin=open(full_fname), stdout=PIPE, stderr=PIPE)
-    else:
         full_cmd = ipython_cmd + cmdargs + [full_fname]
         p = Popen(full_cmd, stdout=PIPE, stderr=PIPE)
     out, err = p.communicate()

IPython/utils/io.py

@@ -42,6 +42,11 b' class IOStream:'
         for meth in filter(clone, dir(stream)):
             setattr(self, meth, getattr(stream, meth))
 
+    def __repr__(self):
+        cls = self.__class__
+        tpl = '{mod}.{cls}({args})'
+        return tpl.format(mod=cls.__module__, cls=cls.__name__, args=self.stream)
+
     def write(self,data):
         try:
             self._swrite(data)