Check that Shift+Tab cycles back

Author: sio

.gitignore

@@ -1,3 +1,4 @@
 /Makefile.venv
 /.venv
 *.pyc
+/.hypothesis

tests/common.py

@@ -68,7 +68,7 @@ def __init__(self, *a,
         for command in chain(self.STARTUP, startup or ()):
             self.execute(command)
 
-    def complete(self, text, tabs=1, drop_colors=True):
+    def complete(self, text, tabs=1, custom_tabs='', drop_colors=True):
         '''
         Trigger completion after inputting text into interactive bash session
 
@@ -77,7 +77,7 @@ def complete(self, text, tabs=1, drop_colors=True):
         self._clear_current_line()
 
         proc = self.process
-        proc.send('{}{}'.format(text, '\t' * tabs))
+        proc.send('{}{}'.format(text, custom_tabs or '\t' * tabs))
         proc.expect_exact(text)
         proc.send(self.MARKER)
         match = proc.expect(re.escape(self.MARKER))

tests/requirements.txt

@@ -1,2 +1,3 @@
 pexpect
 pytest
+hypothesis

tests/test_tabkey.py

@@ -3,6 +3,12 @@
 '''
 
 
+from hypothesis import (
+    given,
+    settings,
+    strategies as st,
+)
+
 class TestShortcuts:
 
     def test_tab_cycles(self, bash):
@@ -15,3 +21,28 @@ def test_tab_cycles(self, bash):
             assert completion == next_cycle, 'tabs: {}, old: {}, new: {}'.format(
                                                 tabs, completion.selected, next_cycle.selected)
 
+    @settings(deadline=1000, max_examples=10)
+    @given(forward = st.integers(min_value=1, max_value=15),
+           backward = st.integers(min_value=1, max_value=15))
+    def test_shift_tab(self, bash, log, forward, backward):
+        '''Shift-Tab cycles back'''
+        command = 'ls u/s/a'
+        cycle_length = len(bash.complete(command)) + 1
+
+        TAB = '\t'
+        SHIFT_TAB = '\x1b\x5b\x5a'  # use 'showkey -a' on any Linux machine
+                                    # to see ASCII codes corresponding to keypresses
+
+        tabs_forward = TAB * ((forward - backward) % cycle_length)
+        if not tabs_forward:  # in case we cycle back to the original command
+            tabs_forward = TAB + SHIFT_TAB
+        tabs_forward_and_back = TAB * forward + SHIFT_TAB * backward
+        log.debug(
+            '[%s/%s] tab sequences: forward=%r, forward and back=%r',
+            forward,
+            backward,
+            tabs_forward,
+            tabs_forward_and_back
+        )
+        assert bash.complete(command, custom_tabs=tabs_forward) == \
+               bash.complete(command, custom_tabs=tabs_forward_and_back)