helix - Unnamed repository; edit this file 'description' to name the repository.


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
use std::iter;

use ropey::iter::Chars;
use tree_sitter::{Node, QueryCursor};

use crate::{
    chars::{categorize_char, char_is_line_ending, CharCategory},
    coords_at_pos,
    graphemes::{
        next_grapheme_boundary, nth_next_grapheme_boundary, nth_prev_grapheme_boundary,
        prev_grapheme_boundary,
    },
    line_ending::rope_is_line_ending,
    pos_at_coords,
    syntax::LanguageConfiguration,
    textobject::TextObject,
    Position, Range, RopeSlice,
};

#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum Direction {
    Forward,
    Backward,
}

#[derive(Copy, Clone, PartialEq, Eq)]
pub enum Movement {
    Extend,
    Move,
}

pub fn move_horizontally(
    slice: RopeSlice,
    range: Range,
    dir: Direction,
    count: usize,
    behaviour: Movement,
) -> Range {
    let pos = range.cursor(slice);

    // Compute the new position.
    let new_pos = match dir {
        Direction::Forward => nth_next_grapheme_boundary(slice, pos, count),
        Direction::Backward => nth_prev_grapheme_boundary(slice, pos, count),
    };

    // Compute the final new range.
    range.put_cursor(slice, new_pos, behaviour == Movement::Extend)
}

pub fn move_vertically(
    slice: RopeSlice,
    range: Range,
    dir: Direction,
    count: usize,
    behaviour: Movement,
) -> Range {
    let pos = range.cursor(slice);

    // Compute the current position's 2d coordinates.
    // TODO: switch this to use `visual_coords_at_pos` rather than
    // `coords_at_pos` as this will cause a jerky movement when the visual
    // position does not match, like moving from a line with tabs/CJK to
    // a line without
    let Position { row, col } = coords_at_pos(slice, pos);
    let horiz = range.horiz.unwrap_or(col as u32);

    // Compute the new position.
    let new_row = match dir {
        Direction::Forward => (row + count).min(slice.len_lines().saturating_sub(1)),
        Direction::Backward => row.saturating_sub(count),
    };
    let new_col = col.max(horiz as usize);
    let new_pos = pos_at_coords(slice, Position::new(new_row, new_col), true);

    // Special-case to avoid moving to the end of the last non-empty line.
    if behaviour == Movement::Extend && slice.line(new_row).len_chars() == 0 {
        return range;
    }

    let mut new_range = range.put_cursor(slice, new_pos, behaviour == Movement::Extend);
    new_range.horiz = Some(horiz);
    new_range
}

pub fn move_next_word_start(slice: RopeSlice, range: Range, count: usize) -> Range {
    word_move(slice, range, count, WordMotionTarget::NextWordStart)
}

pub fn move_next_word_end(slice: RopeSlice, range: Range, count: usize) -> Range {
    word_move(slice, range, count, WordMotionTarget::NextWordEnd)
}

pub fn move_prev_word_start(slice: RopeSlice, range: Range, count: usize) -> Range {
    word_move(slice, range, count, WordMotionTarget::PrevWordStart)
}

pub fn move_next_long_word_start(slice: RopeSlice, range: Range, count: usize) -> Range {
    word_move(slice, range, count, WordMotionTarget::NextLongWordStart)
}

pub fn move_next_long_word_end(slice: RopeSlice, range: Range, count: usize) -> Range {
    word_move(slice, range, count, WordMotionTarget::NextLongWordEnd)
}

pub fn move_prev_long_word_start(slice: RopeSlice, range: Range, count: usize) -> Range {
    word_move(slice, range, count, WordMotionTarget::PrevLongWordStart)
}

pub fn move_prev_word_end(slice: RopeSlice, range: Range, count: usize) -> Range {
    word_move(slice, range, count, WordMotionTarget::PrevWordEnd)
}

fn word_move(slice: RopeSlice, range: Range, count: usize, target: WordMotionTarget) -> Range {
    let is_prev = matches!(
        target,
        WordMotionTarget::PrevWordStart
            | WordMotionTarget::PrevLongWordStart
            | WordMotionTarget::PrevWordEnd
    );

    // Special-case early-out.
    if (is_prev && range.head == 0) || (!is_prev && range.head == slice.len_chars()) {
        return range;
    }

    // Prepare the range appropriately based on the target movement
    // direction.  This is addressing two things at once:
    //
    //   1. Block-cursor semantics.
    //   2. The anchor position being irrelevant to the output result.
    #[allow(clippy::collapsible_else_if)] // Makes the structure clearer in this case.
    let start_range = if is_prev {
        if range.anchor < range.head {
            Range::new(range.head, prev_grapheme_boundary(slice, range.head))
        } else {
            Range::new(next_grapheme_boundary(slice, range.head), range.head)
        }
    } else {
        if range.anchor < range.head {
            Range::new(prev_grapheme_boundary(slice, range.head), range.head)
        } else {
            Range::new(range.head, next_grapheme_boundary(slice, range.head))
        }
    };

    // Do the main work.
    (0..count).fold(start_range, |r, _| {
        slice.chars_at(r.head).range_to_target(target, r)
    })
}

pub fn move_prev_paragraph(
    slice: RopeSlice,
    range: Range,
    count: usize,
    behavior: Movement,
) -> Range {
    let mut line = range.cursor_line(slice);
    let first_char = slice.line_to_char(line) == range.cursor(slice);
    let prev_line_empty = rope_is_line_ending(slice.line(line.saturating_sub(1)));
    let curr_line_empty = rope_is_line_ending(slice.line(line));
    let prev_empty_to_line = prev_line_empty && !curr_line_empty;

    // skip character before paragraph boundary
    if prev_empty_to_line && !first_char {
        line += 1;
    }
    let mut lines = slice.lines_at(line);
    lines.reverse();
    let mut lines = lines.map(rope_is_line_ending).peekable();
    for _ in 0..count {
        while lines.next_if(|&e| e).is_some() {
            line -= 1;
        }
        while lines.next_if(|&e| !e).is_some() {
            line -= 1;
        }
    }

    let head = slice.line_to_char(line);
    let anchor = if behavior == Movement::Move {
        // exclude first character after paragraph boundary
        if prev_empty_to_line && first_char {
            range.cursor(slice)
        } else {
            range.head
        }
    } else {
        range.put_cursor(slice, head, true).anchor
    };
    Range::new(anchor, head)
}

pub fn move_next_paragraph(
    slice: RopeSlice,
    range: Range,
    count: usize,
    behavior: Movement,
) -> Range {
    let mut line = range.cursor_line(slice);
    let last_char =
        prev_grapheme_boundary(slice, slice.line_to_char(line + 1)) == range.cursor(slice);
    let curr_line_empty = rope_is_line_ending(slice.line(line));
    let next_line_empty =
        rope_is_line_ending(slice.line(slice.len_lines().saturating_sub(1).min(line + 1)));
    let curr_empty_to_line = curr_line_empty && !next_line_empty;

    // skip character after paragraph boundary
    if curr_empty_to_line && last_char {
        line += 1;
    }
    let mut lines = slice.lines_at(line).map(rope_is_line_ending).peekable();
    for _ in 0..count {
        while lines.next_if(|&e| !e).is_some() {
            line += 1;
        }
        while lines.next_if(|&e| e).is_some() {
            line += 1;
        }
    }
    let head = slice.line_to_char(line);
    let anchor = if behavior == Movement::Move {
        if curr_empty_to_line && last_char {
            range.head
        } else {
            range.cursor(slice)
        }
    } else {
        range.put_cursor(slice, head, true).anchor
    };
    Range::new(anchor, head)
}

// ---- util ------------

#[inline]
/// Returns first index that doesn't satisfy a given predicate when
/// advancing the character index.
///
/// Returns none if all characters satisfy the predicate.
pub fn skip_while<F>(slice: RopeSlice, pos: usize, fun: F) -> Option<usize>
where
    F: Fn(char) -> bool,
{
    let mut chars = slice.chars_at(pos).enumerate();
    chars.find_map(|(i, c)| if !fun(c) { Some(pos + i) } else { None })
}

#[inline]
/// Returns first index that doesn't satisfy a given predicate when
/// retreating the character index, saturating if all elements satisfy
/// the condition.
pub fn backwards_skip_while<F>(slice: RopeSlice, pos: usize, fun: F) -> Option<usize>
where
    F: Fn(char) -> bool,
{
    let mut chars_starting_from_next = slice.chars_at(pos);
    let mut backwards = iter::from_fn(|| chars_starting_from_next.prev()).enumerate();
    backwards.find_map(|(i, c)| {
        if !fun(c) {
            Some(pos.saturating_sub(i))
        } else {
            None
        }
    })
}

/// Possible targets of a word motion
#[derive(Copy, Clone, Debug)]
pub enum WordMotionTarget {
    NextWordStart,
    NextWordEnd,
    PrevWordStart,
    PrevWordEnd,
    // A "Long word" (also known as a WORD in vim/kakoune) is strictly
    // delimited by whitespace, and can consist of punctuation as well
    // as alphanumerics.
    NextLongWordStart,
    NextLongWordEnd,
    PrevLongWordStart,
}

pub trait CharHelpers {
    fn range_to_target(&mut self, target: WordMotionTarget, origin: Range) -> Range;
}

impl CharHelpers for Chars<'_> {
    /// Note: this only changes the anchor of the range if the head is effectively
    /// starting on a boundary (either directly or after skipping newline characters).
    /// Any other changes to the anchor should be handled by the calling code.
    fn range_to_target(&mut self, target: WordMotionTarget, origin: Range) -> Range {
        let is_prev = matches!(
            target,
            WordMotionTarget::PrevWordStart
                | WordMotionTarget::PrevLongWordStart
                | WordMotionTarget::PrevWordEnd
        );

        // Reverse the iterator if needed for the motion direction.
        if is_prev {
            self.reverse();
        }

        // Function to advance index in the appropriate motion direction.
        let advance: &dyn Fn(&mut usize) = if is_prev {
            &|idx| *idx = idx.saturating_sub(1)
        } else {
            &|idx| *idx += 1
        };

        // Initialize state variables.
        let mut anchor = origin.anchor;
        let mut head = origin.head;
        let mut prev_ch = {
            let ch = self.prev();
            if ch.is_some() {
                self.next();
            }
            ch
        };

        // Skip any initial newline characters.
        while let Some(ch) = self.next() {
            if char_is_line_ending(ch) {
                prev_ch = Some(ch);
                advance(&mut head);
            } else {
                self.prev();
                break;
            }
        }
        if prev_ch.map(char_is_line_ending).unwrap_or(false) {
            anchor = head;
        }

        // Find our target position(s).
        let head_start = head;
        #[allow(clippy::while_let_on_iterator)] // Clippy's suggestion to fix doesn't work here.
        while let Some(next_ch) = self.next() {
            if prev_ch.is_none() || reached_target(target, prev_ch.unwrap(), next_ch) {
                if head == head_start {
                    anchor = head;
                } else {
                    break;
                }
            }
            prev_ch = Some(next_ch);
            advance(&mut head);
        }

        // Un-reverse the iterator if needed.
        if is_prev {
            self.reverse();
        }

        Range::new(anchor, head)
    }
}

fn is_word_boundary(a: char, b: char) -> bool {
    categorize_char(a) != categorize_char(b)
}

fn is_long_word_boundary(a: char, b: char) -> bool {
    match (categorize_char(a), categorize_char(b)) {
        (CharCategory::Word, CharCategory::Punctuation)
        | (CharCategory::Punctuation, CharCategory::Word) => false,
        (a, b) if a != b => true,
        _ => false,
    }
}

fn reached_target(target: WordMotionTarget, prev_ch: char, next_ch: char) -> bool {
    match target {
        WordMotionTarget::NextWordStart | WordMotionTarget::PrevWordEnd => {
            is_word_boundary(prev_ch, next_ch)
                && (char_is_line_ending(next_ch) || !next_ch.is_whitespace())
        }
        WordMotionTarget::NextWordEnd | WordMotionTarget::PrevWordStart => {
            is_word_boundary(prev_ch, next_ch)
                && (!prev_ch.is_whitespace() || char_is_line_ending(next_ch))
        }
        WordMotionTarget::NextLongWordStart => {
            is_long_word_boundary(prev_ch, next_ch)
                && (char_is_line_ending(next_ch) || !next_ch.is_whitespace())
        }
        WordMotionTarget::NextLongWordEnd | WordMotionTarget::PrevLongWordStart => {
            is_long_word_boundary(prev_ch, next_ch)
                && (!prev_ch.is_whitespace() || char_is_line_ending(next_ch))
        }
    }
}

pub fn goto_treesitter_object(
    slice: RopeSlice,
    range: Range,
    object_name: &str,
    dir: Direction,
    slice_tree: Node,
    lang_config: &LanguageConfiguration,
    _count: usize,
) -> Range {
    let get_range = move || -> Option<Range> {
        let byte_pos = slice.char_to_byte(range.cursor(slice));

        let cap_name = |t: TextObject| format!("{}.{}", object_name, t);
        let mut cursor = QueryCursor::new();
        let nodes = lang_config.textobject_query()?.capture_nodes_any(
            &[
                &cap_name(TextObject::Movement),
                &cap_name(TextObject::Around),
                &cap_name(TextObject::Inside),
            ],
            slice_tree,
            slice,
            &mut cursor,
        )?;

        let node = match dir {
            Direction::Forward => nodes
                .filter(|n| n.start_byte() > byte_pos)
                .min_by_key(|n| n.start_byte())?,
            Direction::Backward => nodes
                .filter(|n| n.start_byte() < byte_pos)
                .max_by_key(|n| n.start_byte())?,
        };

        let len = slice.len_bytes();
        let start_byte = node.start_byte();
        let end_byte = node.end_byte();
        if start_byte >= len || end_byte >= len {
            return None;
        }

        let start_char = slice.byte_to_char(start_byte);
        let end_char = slice.byte_to_char(end_byte);

        // head of range should be at beginning
        Some(Range::new(end_char, start_char))
    };
    get_range().unwrap_or(range)
}

#[cfg(test)]
mod test {
    use ropey::Rope;

    use super::*;

    const SINGLE_LINE_SAMPLE: &str = "This is a simple alphabetic line";
    const MULTILINE_SAMPLE: &str = "\
        Multiline\n\
        text sample\n\
        which\n\
        is merely alphabetic\n\
        and whitespaced\n\
    ";

    const MULTIBYTE_CHARACTER_SAMPLE: &str = "\
        パーティーへ行かないか\n\
        The text above is Japanese\n\
    ";

    #[test]
    fn test_vertical_move() {
        let text = Rope::from("abcd\nefg\nwrs");
        let slice = text.slice(..);
        let pos = pos_at_coords(slice, (0, 4).into(), true);

        let range = Range::new(pos, pos);
        assert_eq!(
            coords_at_pos(
                slice,
                move_vertically(slice, range, Direction::Forward, 1, Movement::Move).head
            ),
            (1, 3).into()
        );
    }

    #[test]
    fn horizontal_moves_through_single_line_text() {
        let text = Rope::from(SINGLE_LINE_SAMPLE);
        let slice = text.slice(..);
        let position = pos_at_coords(slice, (0, 0).into(), true);

        let mut range = Range::point(position);

        let moves_and_expected_coordinates = [
            ((Direction::Forward, 1usize), (0, 1)), // T|his is a simple alphabetic line
            ((Direction::Forward, 2usize), (0, 3)), // Thi|s is a simple alphabetic line
            ((Direction::Forward, 0usize), (0, 3)), // Thi|s is a simple alphabetic line
            ((Direction::Forward, 999usize), (0, 32)), // This is a simple alphabetic line|
            ((Direction::Forward, 999usize), (0, 32)), // This is a simple alphabetic line|
            ((Direction::Backward, 999usize), (0, 0)), // |This is a simple alphabetic line
        ];

        for ((direction, amount), coordinates) in moves_and_expected_coordinates {
            range = move_horizontally(slice, range, direction, amount, Movement::Move);
            assert_eq!(coords_at_pos(slice, range.head), coordinates.into())
        }
    }

    #[test]
    fn horizontal_moves_through_multiline_text() {
        let text = Rope::from(MULTILINE_SAMPLE);
        let slice = text.slice(..);
        let position = pos_at_coords(slice, (0, 0).into(), true);

        let mut range = Range::point(position);

        let moves_and_expected_coordinates = [
            ((Direction::Forward, 11usize), (1, 1)), // Multiline\nt|ext sample\n...
            ((Direction::Backward, 1usize), (1, 0)), // Multiline\n|text sample\n...
            ((Direction::Backward, 5usize), (0, 5)), // Multi|line\ntext sample\n...
            ((Direction::Backward, 999usize), (0, 0)), // |Multiline\ntext sample\n...
            ((Direction::Forward, 3usize), (0, 3)),  // Mul|tiline\ntext sample\n...
            ((Direction::Forward, 0usize), (0, 3)),  // Mul|tiline\ntext sample\n...
            ((Direction::Backward, 0usize), (0, 3)), // Mul|tiline\ntext sample\n...
            ((Direction::Forward, 999usize), (5, 0)), // ...and whitespaced\n|
            ((Direction::Forward, 999usize), (5, 0)), // ...and whitespaced\n|
        ];

        for ((direction, amount), coordinates) in moves_and_expected_coordinates {
            range = move_horizontally(slice, range, direction, amount, Movement::Move);
            assert_eq!(coords_at_pos(slice, range.head), coordinates.into());
            assert_eq!(range.head, range.anchor);
        }
    }

    #[test]
    fn selection_extending_moves_in_single_line_text() {
        let text = Rope::from(SINGLE_LINE_SAMPLE);
        let slice = text.slice(..);
        let position = pos_at_coords(slice, (0, 0).into(), true);

        let mut range = Range::point(position);
        let original_anchor = range.anchor;

        let moves = [
            (Direction::Forward, 1usize),
            (Direction::Forward, 5usize),
            (Direction::Backward, 3usize),
        ];

        for (direction, amount) in moves {
            range = move_horizontally(slice, range, direction, amount, Movement::Extend);
            assert_eq!(range.anchor, original_anchor);
        }
    }

    #[test]
    fn vertical_moves_in_single_column() {
        let text = Rope::from(MULTILINE_SAMPLE);
        let slice = text.slice(..);
        let position = pos_at_coords(slice, (0, 0).into(), true);
        let mut range = Range::point(position);
        let moves_and_expected_coordinates = [
            ((Direction::Forward, 1usize), (1, 0)),
            ((Direction::Forward, 2usize), (3, 0)),
            ((Direction::Forward, 1usize), (4, 0)),
            ((Direction::Backward, 999usize), (0, 0)),
            ((Direction::Forward, 4usize), (4, 0)),
            ((Direction::Forward, 0usize), (4, 0)),
            ((Direction::Backward, 0usize), (4, 0)),
            ((Direction::Forward, 5), (5, 0)),
            ((Direction::Forward, 999usize), (5, 0)),
        ];

        for ((direction, amount), coordinates) in moves_and_expected_coordinates {
            range = move_vertically(slice, range, direction, amount, Movement::Move);
            assert_eq!(coords_at_pos(slice, range.head), coordinates.into());
            assert_eq!(range.head, range.anchor);
        }
    }

    #[test]
    fn vertical_moves_jumping_column() {
        let text = Rope::from(MULTILINE_SAMPLE);
        let slice = text.slice(..);
        let position = pos_at_coords(slice, (0, 0).into(), true);
        let mut range = Range::point(position);

        enum Axis {
            H,
            V,
        }
        let moves_and_expected_coordinates = [
            // Places cursor at the end of line
            ((Axis::H, Direction::Forward, 8usize), (0, 8)),
            // First descent preserves column as the target line is wider
            ((Axis::V, Direction::Forward, 1usize), (1, 8)),
            // Second descent clamps column as the target line is shorter
            ((Axis::V, Direction::Forward, 1usize), (2, 5)),
            // Third descent restores the original column
            ((Axis::V, Direction::Forward, 1usize), (3, 8)),
            // Behaviour is preserved even through long jumps
            ((Axis::V, Direction::Backward, 999usize), (0, 8)),
            ((Axis::V, Direction::Forward, 4usize), (4, 8)),
            ((Axis::V, Direction::Forward, 999usize), (5, 0)),
        ];

        for ((axis, direction, amount), coordinates) in moves_and_expected_coordinates {
            range = match axis {
                Axis::H => move_horizontally(slice, range, direction, amount, Movement::Move),
                Axis::V => move_vertically(slice, range, direction, amount, Movement::Move),
            };
            assert_eq!(coords_at_pos(slice, range.head), coordinates.into());
            assert_eq!(range.head, range.anchor);
        }
    }

    #[test]
    fn multibyte_character_wide_column_jumps() {
        let text = Rope::from(MULTIBYTE_CHARACTER_SAMPLE);
        let slice = text.slice(..);
        let position = pos_at_coords(slice, (0, 0).into(), true);
        let mut range = Range::point(position);

        // FIXME: The behaviour captured in this test diverges from both Kakoune and Vim. These
        // will attempt to preserve the horizontal position of the cursor, rather than
        // placing it at the same character index.
        enum Axis {
            H,
            V,
        }
        let moves_and_expected_coordinates = [
            // Places cursor at the fourth kana.
            ((Axis::H, Direction::Forward, 4), (0, 4)),
            // Descent places cursor at the 4th character.
            ((Axis::V, Direction::Forward, 1usize), (1, 4)),
            // Moving back 1 character.
            ((Axis::H, Direction::Backward, 1usize), (1, 3)),
            // Jumping back up 1 line.
            ((Axis::V, Direction::Backward, 1usize), (0, 3)),
        ];

        for ((axis, direction, amount), coordinates) in moves_and_expected_coordinates {
            range = match axis {
                Axis::H => move_horizontally(slice, range, direction, amount, Movement::Move),
                Axis::V => move_vertically(slice, range, direction, amount, Movement::Move),
            };
            assert_eq!(coords_at_pos(slice, range.head), coordinates.into());
            assert_eq!(range.head, range.anchor);
        }
    }

    #[test]
    #[should_panic]
    fn nonsensical_ranges_panic_on_forward_movement_attempt_in_debug_mode() {
        move_next_word_start(Rope::from("Sample").slice(..), Range::point(99999999), 1);
    }

    #[test]
    #[should_panic]
    fn nonsensical_ranges_panic_on_forward_to_end_movement_attempt_in_debug_mode() {
        move_next_word_end(Rope::from("Sample").slice(..), Range::point(99999999), 1);
    }

    #[test]
    #[should_panic]
    fn nonsensical_ranges_panic_on_backwards_movement_attempt_in_debug_mode() {
        move_prev_word_start(Rope::from("Sample").slice(..), Range::point(99999999), 1);
    }

    #[test]
    fn test_behaviour_when_moving_to_start_of_next_words() {
        let tests = [
            ("Basic forward motion stops at the first space",
                vec![(1, Range::new(0, 0), Range::new(0, 6))]),
            (" Starting from a boundary advances the anchor",
                vec![(1, Range::new(0, 0), Range::new(1, 10))]),
            ("Long       whitespace gap is bridged by the head",
                vec![(1, Range::new(0, 0), Range::new(0, 11))]),
            ("Previous anchor is irrelevant for forward motions",
                vec![(1, Range::new(12, 0), Range::new(0, 9))]),
            ("    Starting from whitespace moves to last space in sequence",
                vec![(1, Range::new(0, 0), Range::new(0, 4))]),
            ("Starting from mid-word leaves anchor at start position and moves head",
                vec![(1, Range::new(3, 3), Range::new(3, 9))]),
            ("Identifiers_with_underscores are considered a single word",
                vec![(1, Range::new(0, 0), Range::new(0, 29))]),
            ("Jumping\n    into starting whitespace selects the spaces before 'into'",
                vec![(1, Range::new(0, 7), Range::new(8, 12))]),
            ("alphanumeric.!,and.?=punctuation are considered 'words' for the purposes of word motion",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 12)),
                    (1, Range::new(0, 12), Range::new(12, 15)),
                    (1, Range::new(12, 15), Range::new(15, 18))
                ]),
            ("...   ... punctuation and spaces behave as expected",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 6)),
                    (1, Range::new(0, 6), Range::new(6, 10)),
                ]),
            (".._.._ punctuation is not joined by underscores into a single block",
                vec![(1, Range::new(0, 0), Range::new(0, 2))]),
            ("Newlines\n\nare bridged seamlessly.",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 8)),
                    (1, Range::new(0, 8), Range::new(10, 14)),
                ]),
            ("Jumping\n\n\n\n\n\n   from newlines to whitespace selects whitespace.",
                vec![
                    (1, Range::new(0, 9), Range::new(13, 16)),
                ]),
            ("A failed motion does not modify the range",
                vec![
                    (3, Range::new(37, 41), Range::new(37, 41)),
                ]),
            ("oh oh oh two character words!",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 3)),
                    (1, Range::new(0, 3), Range::new(3, 6)),
                    (1, Range::new(0, 2), Range::new(1, 3)),
                ]),
            ("Multiple motions at once resolve correctly",
                vec![
                    (3, Range::new(0, 0), Range::new(17, 20)),
                ]),
            ("Excessive motions are performed partially",
                vec![
                    (999, Range::new(0, 0), Range::new(32, 41)),
                ]),
            ("", // Edge case of moving forward in empty string
                vec![
                    (1, Range::new(0, 0), Range::new(0, 0)),
                ]),
            ("\n\n\n\n\n", // Edge case of moving forward in all newlines
                vec![
                    (1, Range::new(0, 0), Range::new(5, 5)),
                ]),
            ("\n   \n   \n Jumping through alternated space blocks and newlines selects the space blocks",
                vec![
                    (1, Range::new(0, 0), Range::new(1, 4)),
                    (1, Range::new(1, 4), Range::new(5, 8)),
                ]),
            ("ヒーリクス multibyte characters behave as normal characters",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 6)),
                ]),
        ];

        for (sample, scenario) in tests {
            for (count, begin, expected_end) in scenario.into_iter() {
                let range = move_next_word_start(Rope::from(sample).slice(..), begin, count);
                assert_eq!(range, expected_end, "Case failed: [{}]", sample);
            }
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_start_of_next_long_words() {
        let tests = [
            ("Basic forward motion stops at the first space",
                vec![(1, Range::new(0, 0), Range::new(0, 6))]),
            (" Starting from a boundary advances the anchor",
                vec![(1, Range::new(0, 0), Range::new(1, 10))]),
            ("Long       whitespace gap is bridged by the head",
                vec![(1, Range::new(0, 0), Range::new(0, 11))]),
            ("Previous anchor is irrelevant for forward motions",
                vec![(1, Range::new(12, 0), Range::new(0, 9))]),
            ("    Starting from whitespace moves to last space in sequence",
                vec![(1, Range::new(0, 0), Range::new(0, 4))]),
            ("Starting from mid-word leaves anchor at start position and moves head",
                vec![(1, Range::new(3, 3), Range::new(3, 9))]),
            ("Identifiers_with_underscores are considered a single word",
                vec![(1, Range::new(0, 0), Range::new(0, 29))]),
            ("Jumping\n    into starting whitespace selects the spaces before 'into'",
                vec![(1, Range::new(0, 7), Range::new(8, 12))]),
            ("alphanumeric.!,and.?=punctuation are not treated any differently than alphanumerics",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 33)),
                ]),
            ("...   ... punctuation and spaces behave as expected",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 6)),
                    (1, Range::new(0, 6), Range::new(6, 10)),
                ]),
            (".._.._ punctuation is joined by underscores into a single word, as it behaves like alphanumerics",
                vec![(1, Range::new(0, 0), Range::new(0, 7))]),
            ("Newlines\n\nare bridged seamlessly.",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 8)),
                    (1, Range::new(0, 8), Range::new(10, 14)),
                ]),
            ("Jumping\n\n\n\n\n\n   from newlines to whitespace selects whitespace.",
                vec![
                    (1, Range::new(0, 9), Range::new(13, 16)),
                ]),
            ("A failed motion does not modify the range",
                vec![
                    (3, Range::new(37, 41), Range::new(37, 41)),
                ]),
            ("oh oh oh two character words!",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 3)),
                    (1, Range::new(0, 3), Range::new(3, 6)),
                    (1, Range::new(0, 1), Range::new(0, 3)),
                ]),
            ("Multiple motions at once resolve correctly",
                vec![
                    (3, Range::new(0, 0), Range::new(17, 20)),
                ]),
            ("Excessive motions are performed partially",
                vec![
                    (999, Range::new(0, 0), Range::new(32, 41)),
                ]),
            ("", // Edge case of moving forward in empty string
                vec![
                    (1, Range::new(0, 0), Range::new(0, 0)),
                ]),
            ("\n\n\n\n\n", // Edge case of moving forward in all newlines
                vec![
                    (1, Range::new(0, 0), Range::new(5, 5)),
                ]),
            ("\n   \n   \n Jumping through alternated space blocks and newlines selects the space blocks",
                vec![
                    (1, Range::new(0, 0), Range::new(1, 4)),
                    (1, Range::new(1, 4), Range::new(5, 8)),
                ]),
            ("ヒー..リクス multibyte characters behave as normal characters, including their interaction with punctuation",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 8)),
                ]),
        ];

        for (sample, scenario) in tests {
            for (count, begin, expected_end) in scenario.into_iter() {
                let range = move_next_long_word_start(Rope::from(sample).slice(..), begin, count);
                assert_eq!(range, expected_end, "Case failed: [{}]", sample);
            }
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_start_of_previous_words() {
        let tests = [
            ("Basic backward motion from the middle of a word",
                vec![(1, Range::new(3, 3), Range::new(4, 0))]),

            // // Why do we want this behavior?  The current behavior fails this
            // // test, but seems better and more consistent.
            // ("Starting from after boundary retreats the anchor",
            //     vec![(1, Range::new(0, 9), Range::new(8, 0))]),

            ("    Jump to start of a word preceded by whitespace",
                vec![(1, Range::new(5, 5), Range::new(6, 4))]),
            ("    Jump to start of line from start of word preceded by whitespace",
                vec![(1, Range::new(4, 4), Range::new(4, 0))]),
            ("Previous anchor is irrelevant for backward motions",
                vec![(1, Range::new(12, 5), Range::new(6, 0))]),
            ("    Starting from whitespace moves to first space in sequence",
                vec![(1, Range::new(0, 4), Range::new(4, 0))]),
            ("Identifiers_with_underscores are considered a single word",
                vec![(1, Range::new(0, 20), Range::new(20, 0))]),
            ("Jumping\n    \nback through a newline selects whitespace",
                vec![(1, Range::new(0, 13), Range::new(12, 8))]),
            ("Jumping to start of word from the end selects the word",
                vec![(1, Range::new(6, 7), Range::new(7, 0))]),
            ("alphanumeric.!,and.?=punctuation are considered 'words' for the purposes of word motion",
                vec![
                    (1, Range::new(29, 30), Range::new(30, 21)),
                    (1, Range::new(30, 21), Range::new(21, 18)),
                    (1, Range::new(21, 18), Range::new(18, 15))
                ]),
            ("...   ... punctuation and spaces behave as expected",
                vec![
                    (1, Range::new(0, 10), Range::new(10, 6)),
                    (1, Range::new(10, 6), Range::new(6, 0)),
                ]),
            (".._.._ punctuation is not joined by underscores into a single block",
                vec![(1, Range::new(0, 6), Range::new(5, 3))]),
            ("Newlines\n\nare bridged seamlessly.",
                vec![
                    (1, Range::new(0, 10), Range::new(8, 0)),
                ]),
            ("Jumping    \n\n\n\n\nback from within a newline group selects previous block",
                vec![
                    (1, Range::new(0, 13), Range::new(11, 0)),
                ]),
            ("Failed motions do not modify the range",
                vec![
                    (0, Range::new(3, 0), Range::new(3, 0)),
                ]),
            ("Multiple motions at once resolve correctly",
                vec![
                    (3, Range::new(18, 18), Range::new(9, 0)),
                ]),
            ("Excessive motions are performed partially",
                vec![
                    (999, Range::new(40, 40), Range::new(10, 0)),
                ]),
            ("", // Edge case of moving backwards in empty string
                vec![
                    (1, Range::new(0, 0), Range::new(0, 0)),
                ]),
            ("\n\n\n\n\n", // Edge case of moving backwards in all newlines
                vec![
                    (1, Range::new(5, 5), Range::new(0, 0)),
                ]),
            ("   \n   \nJumping back through alternated space blocks and newlines selects the space blocks",
                vec![
                    (1, Range::new(0, 8), Range::new(7, 4)),
                    (1, Range::new(7, 4), Range::new(3, 0)),
                ]),
            ("ヒーリクス multibyte characters behave as normal characters",
                vec![
                    (1, Range::new(0, 6), Range::new(6, 0)),
                ]),
        ];

        for (sample, scenario) in tests {
            for (count, begin, expected_end) in scenario.into_iter() {
                let range = move_prev_word_start(Rope::from(sample).slice(..), begin, count);
                assert_eq!(range, expected_end, "Case failed: [{}]", sample);
            }
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_start_of_previous_long_words() {
        let tests = [
            (
                "Basic backward motion from the middle of a word",
                vec![(1, Range::new(3, 3), Range::new(4, 0))],
            ),

            // // Why do we want this behavior?  The current behavior fails this
            // // test, but seems better and more consistent.
            // ("Starting from after boundary retreats the anchor",
            //     vec![(1, Range::new(0, 9), Range::new(8, 0))]),

            (
                "    Jump to start of a word preceded by whitespace",
                vec![(1, Range::new(5, 5), Range::new(6, 4))],
            ),
            (
                "    Jump to start of line from start of word preceded by whitespace",
                vec![(1, Range::new(3, 4), Range::new(4, 0))],
            ),
            ("Previous anchor is irrelevant for backward motions",
                vec![(1, Range::new(12, 5), Range::new(6, 0))]),
            (
                "    Starting from whitespace moves to first space in sequence",
                vec![(1, Range::new(0, 4), Range::new(4, 0))],
            ),
            ("Identifiers_with_underscores are considered a single word",
                vec![(1, Range::new(0, 20), Range::new(20, 0))]),
            (
                "Jumping\n    \nback through a newline selects whitespace",
                vec![(1, Range::new(0, 13), Range::new(12, 8))],
            ),
            (
                "Jumping to start of word from the end selects the word",
                vec![(1, Range::new(6, 7), Range::new(7, 0))],
            ),
            (
                "alphanumeric.!,and.?=punctuation are treated exactly the same",
                vec![(1, Range::new(29, 30), Range::new(30, 0))],
            ),
            (
                "...   ... punctuation and spaces behave as expected",
                vec![
                    (1, Range::new(0, 10), Range::new(10, 6)),
                    (1, Range::new(10, 6), Range::new(6, 0)),
                ],
            ),
            (".._.._ punctuation is joined by underscores into a single block",
                vec![(1, Range::new(0, 6), Range::new(6, 0))]),
            (
                "Newlines\n\nare bridged seamlessly.",
                vec![(1, Range::new(0, 10), Range::new(8, 0))],
            ),
            (
                "Jumping    \n\n\n\n\nback from within a newline group selects previous block",
                vec![(1, Range::new(0, 13), Range::new(11, 0))],
            ),
            (
                "Failed motions do not modify the range",
                vec![(0, Range::new(3, 0), Range::new(3, 0))],
            ),
            (
                "Multiple motions at once resolve correctly",
                vec![(3, Range::new(19, 19), Range::new(9, 0))],
            ),
            (
                "Excessive motions are performed partially",
                vec![(999, Range::new(40, 40), Range::new(10, 0))],
            ),
            (
                "", // Edge case of moving backwards in empty string
                vec![(1, Range::new(0, 0), Range::new(0, 0))],
            ),
            (
                "\n\n\n\n\n", // Edge case of moving backwards in all newlines
                vec![(1, Range::new(5, 5), Range::new(0, 0))],
            ),
            ("   \n   \nJumping back through alternated space blocks and newlines selects the space blocks",
                vec![
                    (1, Range::new(0, 8), Range::new(7, 4)),
                    (1, Range::new(7, 4), Range::new(3, 0)),
                ]),
            ("ヒーリ..クス multibyte characters behave as normal characters, including when interacting with punctuation",
                vec![
                    (1, Range::new(0, 8), Range::new(8, 0)),
                ]),
        ];

        for (sample, scenario) in tests {
            for (count, begin, expected_end) in scenario.into_iter() {
                let range = move_prev_long_word_start(Rope::from(sample).slice(..), begin, count);
                assert_eq!(range, expected_end, "Case failed: [{}]", sample);
            }
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_end_of_next_words() {
        let tests = [
            ("Basic forward motion from the start of a word to the end of it",
                vec![(1, Range::new(0, 0), Range::new(0, 5))]),
            ("Basic forward motion from the end of a word to the end of the next",
                vec![(1, Range::new(0, 5), Range::new(5, 13))]),
            ("Basic forward motion from the middle of a word to the end of it",
                vec![(1, Range::new(2, 2), Range::new(2, 5))]),
            ("    Jumping to end of a word preceded by whitespace",
                vec![(1, Range::new(0, 0), Range::new(0, 11))]),

            // // Why do we want this behavior?  The current behavior fails this
            // // test, but seems better and more consistent.
            // (" Starting from a boundary advances the anchor",
            //     vec![(1, Range::new(0, 0), Range::new(1, 9))]),

            ("Previous anchor is irrelevant for end of word motion",
                vec![(1, Range::new(12, 2), Range::new(2, 8))]),
            ("Identifiers_with_underscores are considered a single word",
                vec![(1, Range::new(0, 0), Range::new(0, 28))]),
            ("Jumping\n    into starting whitespace selects up to the end of next word",
                vec![(1, Range::new(0, 7), Range::new(8, 16))]),
            ("alphanumeric.!,and.?=punctuation are considered 'words' for the purposes of word motion",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 12)),
                    (1, Range::new(0, 12), Range::new(12, 15)),
                    (1, Range::new(12, 15), Range::new(15, 18))
                ]),
            ("...   ... punctuation and spaces behave as expected",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 3)),
                    (1, Range::new(0, 3), Range::new(3, 9)),
                ]),
            (".._.._ punctuation is not joined by underscores into a single block",
                vec![(1, Range::new(0, 0), Range::new(0, 2))]),
            ("Newlines\n\nare bridged seamlessly.",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 8)),
                    (1, Range::new(0, 8), Range::new(10, 13)),
                ]),
            ("Jumping\n\n\n\n\n\n   from newlines to whitespace selects to end of next word.",
                vec![
                    (1, Range::new(0, 8), Range::new(13, 20)),
                ]),
            ("A failed motion does not modify the range",
                vec![
                    (3, Range::new(37, 41), Range::new(37, 41)),
                ]),
            ("Multiple motions at once resolve correctly",
                vec![
                    (3, Range::new(0, 0), Range::new(16, 19)),
                ]),
            ("Excessive motions are performed partially",
                vec![
                    (999, Range::new(0, 0), Range::new(31, 41)),
                ]),
            ("", // Edge case of moving forward in empty string
                vec![
                    (1, Range::new(0, 0), Range::new(0, 0)),
                ]),
            ("\n\n\n\n\n", // Edge case of moving forward in all newlines
                vec![
                    (1, Range::new(0, 0), Range::new(5, 5)),
                ]),
            ("\n   \n   \n Jumping through alternated space blocks and newlines selects the space blocks",
                vec![
                    (1, Range::new(0, 0), Range::new(1, 4)),
                    (1, Range::new(1, 4), Range::new(5, 8)),
                ]),
            ("ヒーリクス multibyte characters behave as normal characters",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 5)),
                ]),
        ];

        for (sample, scenario) in tests {
            for (count, begin, expected_end) in scenario.into_iter() {
                let range = move_next_word_end(Rope::from(sample).slice(..), begin, count);
                assert_eq!(range, expected_end, "Case failed: [{}]", sample);
            }
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_end_of_previous_words() {
        let tests = [
            ("Basic backward motion from the middle of a word",
                vec![(1, Range::new(9, 9), Range::new(10, 5))]),
            ("Starting from after boundary retreats the anchor",
                vec![(1, Range::new(0, 14), Range::new(13, 8))]),
            ("Jump     to end of a word succeeded by whitespace",
                vec![(1, Range::new(11, 11), Range::new(11, 4))]),
            ("    Jump to start of line from end of word preceded by whitespace",
                vec![(1, Range::new(8, 8), Range::new(8, 0))]),
            ("Previous anchor is irrelevant for backward motions",
                vec![(1, Range::new(26, 12), Range::new(13, 8))]),
            ("    Starting from whitespace moves to first space in sequence",
                vec![(1, Range::new(0, 4), Range::new(4, 0))]),
            ("Test identifiers_with_underscores are considered a single word",
                vec![(1, Range::new(0, 25), Range::new(25, 4))]),
            ("Jumping\n    \nback through a newline selects whitespace",
                vec![(1, Range::new(0, 13), Range::new(12, 8))]),
            ("Jumping to start of word from the end selects the whole word",
                vec![(1, Range::new(16, 16), Range::new(16, 10))]),
            ("alphanumeric.!,and.?=punctuation are considered 'words' for the purposes of word motion",
                vec![
                    (1, Range::new(30, 30), Range::new(31, 21)),
                    (1, Range::new(31, 21), Range::new(21, 18)),
                    (1, Range::new(21, 18), Range::new(18, 15))
                ]),

            ("...   ... punctuation and spaces behave as expected",
                vec![
                    (1, Range::new(0, 10), Range::new(9, 3)),
                    (1, Range::new(9, 3), Range::new(3, 0)),
                ]),
            (".._.._ punctuation is not joined by underscores into a single block",
                vec![(1, Range::new(0, 5), Range::new(5, 3))]),
            ("Newlines\n\nare bridged seamlessly.",
                vec![
                    (1, Range::new(0, 10), Range::new(8, 0)),
                ]),
            ("Jumping    \n\n\n\n\nback from within a newline group selects previous block",
                vec![
                    (1, Range::new(0, 13), Range::new(11, 7)),
                ]),
            ("Failed motions do not modify the range",
                vec![
                    (0, Range::new(3, 0), Range::new(3, 0)),
                ]),
            ("Multiple motions at once resolve correctly",
                vec![
                    (3, Range::new(24, 24), Range::new(16, 8)),
                ]),
            ("Excessive motions are performed partially",
                vec![
                    (999, Range::new(40, 40), Range::new(9, 0)),
                ]),
            ("", // Edge case of moving backwards in empty string
                vec![
                    (1, Range::new(0, 0), Range::new(0, 0)),
                ]),
            ("\n\n\n\n\n", // Edge case of moving backwards in all newlines
                vec![
                    (1, Range::new(5, 5), Range::new(0, 0)),
                ]),
            ("   \n   \nJumping back through alternated space blocks and newlines selects the space blocks",
                vec![
                    (1, Range::new(0, 8), Range::new(7, 4)),
                    (1, Range::new(7, 4), Range::new(3, 0)),
                ]),
            ("Test ヒーリクス multibyte characters behave as normal characters",
                vec![
                    (1, Range::new(0, 10), Range::new(10, 4)),
                ]),
        ];

        for (sample, scenario) in tests {
            for (count, begin, expected_end) in scenario.into_iter() {
                let range = move_prev_word_end(Rope::from(sample).slice(..), begin, count);
                assert_eq!(range, expected_end, "Case failed: [{}]", sample);
            }
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_end_of_next_long_words() {
        let tests = [
            ("Basic forward motion from the start of a word to the end of it",
                vec![(1, Range::new(0, 0), Range::new(0, 5))]),
            ("Basic forward motion from the end of a word to the end of the next",
                vec![(1, Range::new(0, 5), Range::new(5, 13))]),
            ("Basic forward motion from the middle of a word to the end of it",
                vec![(1, Range::new(2, 2), Range::new(2, 5))]),
            ("    Jumping to end of a word preceded by whitespace",
                vec![(1, Range::new(0, 0), Range::new(0, 11))]),

            // // Why do we want this behavior?  The current behavior fails this
            // // test, but seems better and more consistent.
            // (" Starting from a boundary advances the anchor",
            //     vec![(1, Range::new(0, 0), Range::new(1, 9))]),

            ("Previous anchor is irrelevant for end of word motion",
                vec![(1, Range::new(12, 2), Range::new(2, 8))]),
            ("Identifiers_with_underscores are considered a single word",
                vec![(1, Range::new(0, 0), Range::new(0, 28))]),
            ("Jumping\n    into starting whitespace selects up to the end of next word",
                vec![(1, Range::new(0, 7), Range::new(8, 16))]),
            ("alphanumeric.!,and.?=punctuation are treated the same way",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 32)),
                ]),
            ("...   ... punctuation and spaces behave as expected",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 3)),
                    (1, Range::new(0, 3), Range::new(3, 9)),
                ]),
            (".._.._ punctuation is joined by underscores into a single block",
                vec![(1, Range::new(0, 0), Range::new(0, 6))]),
            ("Newlines\n\nare bridged seamlessly.",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 8)),
                    (1, Range::new(0, 8), Range::new(10, 13)),
                ]),
            ("Jumping\n\n\n\n\n\n   from newlines to whitespace selects to end of next word.",
                vec![
                    (1, Range::new(0, 9), Range::new(13, 20)),
                ]),
            ("A failed motion does not modify the range",
                vec![
                    (3, Range::new(37, 41), Range::new(37, 41)),
                ]),
            ("Multiple motions at once resolve correctly",
                vec![
                    (3, Range::new(0, 0), Range::new(16, 19)),
                ]),
            ("Excessive motions are performed partially",
                vec![
                    (999, Range::new(0, 0), Range::new(31, 41)),
                ]),
            ("", // Edge case of moving forward in empty string
                vec![
                    (1, Range::new(0, 0), Range::new(0, 0)),
                ]),
            ("\n\n\n\n\n", // Edge case of moving forward in all newlines
                vec![
                    (1, Range::new(0, 0), Range::new(5, 5)),
                ]),
            ("\n   \n   \n Jumping through alternated space blocks and newlines selects the space blocks",
                vec![
                    (1, Range::new(0, 0), Range::new(1, 4)),
                    (1, Range::new(1, 4), Range::new(5, 8)),
                ]),
            ("ヒーリ..クス multibyte characters behave as normal characters, including  when they interact with punctuation",
                vec![
                    (1, Range::new(0, 0), Range::new(0, 7)),
                ]),
        ];

        for (sample, scenario) in tests {
            for (count, begin, expected_end) in scenario.into_iter() {
                let range = move_next_long_word_end(Rope::from(sample).slice(..), begin, count);
                assert_eq!(range, expected_end, "Case failed: [{}]", sample);
            }
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_prev_paragraph_single() {
        let tests = [
            ("#[|]#", "#[|]#"),
            ("#[s|]#tart at\nfirst char\n", "#[|s]#tart at\nfirst char\n"),
            ("start at\nlast char#[\n|]#", "#[|start at\nlast char\n]#"),
            (
                "goto\nfirst\n\n#[p|]#aragraph",
                "#[|goto\nfirst\n\n]#paragraph",
            ),
            (
                "goto\nfirst\n#[\n|]#paragraph",
                "#[|goto\nfirst\n\n]#paragraph",
            ),
            (
                "goto\nsecond\n\np#[a|]#ragraph",
                "goto\nsecond\n\n#[|pa]#ragraph",
            ),
            (
                "here\n\nhave\nmultiple\nparagraph\n\n\n\n\n#[|]#",
                "here\n\n#[|have\nmultiple\nparagraph\n\n\n\n\n]#",
            ),
        ];

        for (before, expected) in tests {
            let (s, selection) = crate::test::print(before);
            let text = Rope::from(s.as_str());
            let selection =
                selection.transform(|r| move_prev_paragraph(text.slice(..), r, 1, Movement::Move));
            let actual = crate::test::plain(&s, selection);
            assert_eq!(actual, expected, "\nbefore: `{:?}`", before);
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_prev_paragraph_double() {
        let tests = [
            (
                "on#[e|]#\n\ntwo\n\nthree\n\n",
                "#[|one]#\n\ntwo\n\nthree\n\n",
            ),
            (
                "one\n\ntwo\n\nth#[r|]#ee\n\n",
                "one\n\n#[|two\n\nthr]#ee\n\n",
            ),
        ];

        for (before, expected) in tests {
            let (s, selection) = crate::test::print(before);
            let text = Rope::from(s.as_str());
            let selection =
                selection.transform(|r| move_prev_paragraph(text.slice(..), r, 2, Movement::Move));
            let actual = crate::test::plain(&s, selection);
            assert_eq!(actual, expected, "\nbefore: `{:?}`", before);
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_prev_paragraph_extend() {
        let tests = [
            (
                "one\n\n#[|two\n\n]#three\n\n",
                "#[|one\n\ntwo\n\n]#three\n\n",
            ),
            (
                "#[|one\n\ntwo\n\n]#three\n\n",
                "#[|one\n\ntwo\n\n]#three\n\n",
            ),
        ];

        for (before, expected) in tests {
            let (s, selection) = crate::test::print(before);
            let text = Rope::from(s.as_str());
            let selection = selection
                .transform(|r| move_prev_paragraph(text.slice(..), r, 1, Movement::Extend));
            let actual = crate::test::plain(&s, selection);
            assert_eq!(actual, expected, "\nbefore: `{:?}`", before);
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_next_paragraph_single() {
        let tests = [
            ("#[|]#", "#[|]#"),
            ("#[s|]#tart at\nfirst char\n", "#[start at\nfirst char\n|]#"),
            ("start at\nlast char#[\n|]#", "start at\nlast char#[\n|]#"),
            (
                "a\nb\n\n#[g|]#oto\nthird\n\nparagraph",
                "a\nb\n\n#[goto\nthird\n\n|]#paragraph",
            ),
            (
                "a\nb\n#[\n|]#goto\nthird\n\nparagraph",
                "a\nb\n\n#[goto\nthird\n\n|]#paragraph",
            ),
            (
                "a\nb#[\n|]#\ngoto\nsecond\n\nparagraph",
                "a\nb#[\n\n|]#goto\nsecond\n\nparagraph",
            ),
            (
                "here\n\nhave\n#[m|]#ultiple\nparagraph\n\n\n\n\n",
                "here\n\nhave\n#[multiple\nparagraph\n\n\n\n\n|]#",
            ),
            (
                "#[t|]#ext\n\n\nafter two blank lines\n\nmore text\n",
                "#[text\n\n\n|]#after two blank lines\n\nmore text\n",
            ),
            (
                "#[text\n\n\n|]#after two blank lines\n\nmore text\n",
                "text\n\n\n#[after two blank lines\n\n|]#more text\n",
            ),
        ];

        for (before, expected) in tests {
            let (s, selection) = crate::test::print(before);
            let text = Rope::from(s.as_str());
            let selection =
                selection.transform(|r| move_next_paragraph(text.slice(..), r, 1, Movement::Move));
            let actual = crate::test::plain(&s, selection);
            assert_eq!(actual, expected, "\nbefore: `{:?}`", before);
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_next_paragraph_double() {
        let tests = [
            (
                "one\n\ntwo\n\nth#[r|]#ee\n\n",
                "one\n\ntwo\n\nth#[ree\n\n|]#",
            ),
            (
                "on#[e|]#\n\ntwo\n\nthree\n\n",
                "on#[e\n\ntwo\n\n|]#three\n\n",
            ),
        ];

        for (before, expected) in tests {
            let (s, selection) = crate::test::print(before);
            let text = Rope::from(s.as_str());
            let selection =
                selection.transform(|r| move_next_paragraph(text.slice(..), r, 2, Movement::Move));
            let actual = crate::test::plain(&s, selection);
            assert_eq!(actual, expected, "\nbefore: `{:?}`", before);
        }
    }

    #[test]
    fn test_behaviour_when_moving_to_next_paragraph_extend() {
        let tests = [
            (
                "one\n\n#[two\n\n|]#three\n\n",
                "one\n\n#[two\n\nthree\n\n|]#",
            ),
            (
                "one\n\n#[two\n\nthree\n\n|]#",
                "one\n\n#[two\n\nthree\n\n|]#",
            ),
        ];

        for (before, expected) in tests {
            let (s, selection) = crate::test::print(before);
            let text = Rope::from(s.as_str());
            let selection = selection
                .transform(|r| move_next_paragraph(text.slice(..), r, 1, Movement::Extend));
            let actual = crate::test::plain(&s, selection);
            assert_eq!(actual, expected, "\nbefore: `{:?}`", before);
        }
    }
}