Add indent / dedent

Resolves #27

tests/indent_test.py

@@ -0,0 +1,101 @@
+from testing.runner import and_exit
+from testing.runner import run
+
+
+def test_indent_at_beginning_of_line():
+    with run() as h, and_exit(h):
+        h.press('hello')
+        h.press('Home')
+        h.press('Tab')
+        h.await_text('\n    hello\n')
+        h.await_cursor_position(x=4, y=1)
+
+
+def test_indent_not_full_tab():
+    with run() as h, and_exit(h):
+        h.press('h')
+        h.press('Tab')
+        h.press('ello')
+        h.await_text('h   ello')
+        h.await_cursor_position(x=8, y=1)
+
+
+def test_indent_fixes_eof():
+    with run() as h, and_exit(h):
+        h.press('Tab')
+        h.press('Down')
+        h.await_cursor_position(x=0, y=2)
+
+
+def test_indent_selection(ten_lines):
+    with run(str(ten_lines)) as h, and_exit(h):
+        h.press('S-Right')
+        h.press('Tab')
+        h.await_text('\n    line_0\n')
+        h.await_cursor_position(x=5, y=1)
+        h.press('^K')
+        h.await_text('\nine_0\n')
+
+
+def test_indent_selection_does_not_extend_mid_line_selection(ten_lines):
+    with run(str(ten_lines)) as h, and_exit(h):
+        h.press('Right')
+        h.press('S-Right')
+        h.press('Tab')
+        h.await_text('\n    line_0\n')
+        h.await_cursor_position(x=6, y=1)
+        h.press('^K')
+        h.await_text('\n    lne_0\n')
+
+
+def test_indent_selection_leaves_blank_lines(tmpdir):
+    f = tmpdir.join('f')
+    f.write('1\n\n2\n\n3\n')
+    with run(str(f)) as h, and_exit(h):
+        for _ in range(3):
+            h.press('S-Down')
+        h.press('Tab')
+        h.press('^S')
+    assert f.read() == '    1\n\n    2\n\n3\n'
+
+
+def test_dedent_no_indentation():
+    with run() as h, and_exit(h):
+        h.press('a')
+        h.press('BTab')
+        h.await_text('\na\n')
+        h.await_cursor_position(x=1, y=1)
+
+
+def test_dedent_exactly_one_indent():
+    with run() as h, and_exit(h):
+        h.press('Tab')
+        h.press('a')
+        h.await_text('\n    a\n')
+        h.press('BTab')
+        h.await_text('\na\n')
+        h.await_cursor_position(x=1, y=1)
+
+
+def test_dedent_selection(tmpdir):
+    f = tmpdir.join('f')
+    f.write('1\n  2\n        3\n')
+    with run(str(f)) as h, and_exit(h):
+        for _ in range(3):
+            h.press('S-Down')
+        h.press('BTab')
+        h.await_text('\n1\n2\n    3\n')
+
+
+def test_dedent_selection_does_not_make_selection_negative():
+    with run() as h, and_exit(h):
+        h.press('Tab')
+        h.press('hello')
+        h.press('Home')
+        h.press('Right')
+        h.press('S-Right')
+        h.press('BTab')
+        h.await_text('\nhello\n')
+        h.press('S-Right')
+        h.press('^K')
+        h.await_text('\nello\n')