Add :sort command

tests/command_mode_test.py

@@ -2,17 +2,7 @@ import pytest
 
 from testing.runner import and_exit
 from testing.runner import run
-
-
-def trigger_command_mode(h):
-    # in order to enter a steady state, trigger an unknown key first and then
-    # press escape to open the command mode.  this is necessary as `Escape` is
-    # the start of "escape sequences" and sending characters too quickly will
-    # be interpreted as a single keypress
-    h.press('^J')
-    h.await_text('unknown key')
-    h.press('Escape')
-    h.await_text_missing('unknown key')
+from testing.runner import trigger_command_mode
 
 
 def test_quit_via_colon_q():

tests/sort_test.py

@@ -0,0 +1,45 @@
+import pytest
+
+from testing.runner import and_exit
+from testing.runner import run
+from testing.runner import trigger_command_mode
+
+
+@pytest.fixture
+def unsorted(tmpdir):
+    f = tmpdir.join('f')
+    f.write('d\nb\nc\na\n')
+    return f
+
+
+def test_sort_entire_file(unsorted):
+    with run(str(unsorted)) as h, and_exit(h):
+        trigger_command_mode(h)
+        h.press_and_enter(':sort')
+        h.await_text('sorted!')
+        h.await_cursor_position(x=0, y=1)
+        h.press('^S')
+    assert unsorted.read() == 'a\nb\nc\nd\n'
+
+
+def test_sort_selection(unsorted):
+    with run(str(unsorted)) as h, and_exit(h):
+        h.press('S-Down')
+        trigger_command_mode(h)
+        h.press_and_enter(':sort')
+        h.await_text('sorted!')
+        h.await_cursor_position(x=0, y=1)
+        h.press('^S')
+    assert unsorted.read() == 'b\nd\nc\na\n'
+
+
+def test_sort_selection_does_not_include_eof(unsorted):
+    with run(str(unsorted)) as h, and_exit(h):
+        for _ in range(5):
+            h.press('S-Down')
+        trigger_command_mode(h)
+        h.press_and_enter(':sort')
+        h.await_text('sorted!')
+        h.await_cursor_position(x=0, y=1)
+        h.press('^S')
+    assert unsorted.read() == 'a\nb\nc\nd\n'