message: add tests for removing multiple characters in edit
diff: @@ -19,16 +19,12 @@ import {diffDeletion, diffAtCaret} from "../../src/editor/diff";
  describe('editor/diff', function() {
  describe('diffDeletion', function() {
  + describe('with a single character removed', function() {
  it('at start of string', function() {
  const diff = diffDeletion("hello", "ello");
  expect(diff.at).toBe(0);
  expect(diff.removed).toBe("h");
  });
  - it('removing whole string', function() {
  - const diff = diffDeletion("hello", "");
  - expect(diff.at).toBe(0);
  - expect(diff.removed).toBe("hello");
  - });
  it('in middle of string', function() {
  const diff = diffDeletion("hello", "hllo");
  expect(diff.at).toBe(1);
  @@ -45,6 +41,34 @@ describe('editor/diff', function() {
  expect(diff.removed).toBe("o");
  });
  });
  + describe('with a multiple removed', function() {
  + it('at start of string', function() {
  + const diff = diffDeletion("hello", "llo");
  + expect(diff.at).toBe(0);
  + expect(diff.removed).toBe("he");
  + });
  + it('removing whole string', function() {
  + const diff = diffDeletion("hello", "");
  + expect(diff.at).toBe(0);
  + expect(diff.removed).toBe("hello");
  + });
  + it('in middle of string', function() {
  + const diff = diffDeletion("hello", "hlo");
  + expect(diff.at).toBe(1);
  + expect(diff.removed).toBe("el");
  + });
  + it('in middle of string with duplicate character', function() {
  + const diff = diffDeletion("hello", "heo");
  + expect(diff.at).toBe(2);
  + expect(diff.removed).toBe("ll");
  + });
  + it('at end of string', function() {
  + const diff = diffDeletion("hello", "hel");
  + expect(diff.at).toBe(3);
  + expect(diff.removed).toBe("lo");
  + });
  + });
  + });
  describe('diffAtCaret', function() {
  it('insert at start', function() {
  const diff = diffAtCaret("world", "hello world", 6);
  