Write integration tests (#719)

* Scaffold a simple test case for debugging

* Set up Jest environment that works with React

- Install and set up react-testing-library
- "Unignore" roughjs and browser-nativejs transformations
- Separate App component from ReactDOM

* Write first passing test

- Mock canvas
- Remove App file and mount/unmount ReactDOM on import

* Add tests for drag create behavior

* Fix comments in dragCreate

* Pin jest-mock-canvas dependency

* Remove dependency range for testing library

* Add tests for multi point mode and selection element

* Fix all tests due to decrease in updates to canvas when changing tools

* Disable state updates if component is unmounted

- Remove all event listeners
- Disable storing scene in state if component is unmounted

* Add tests for move and element selection

* Merge branch 'master' into add-integration-tests

* Add tests for resizing rectangle

* move unmounted check to syncActionResult method

* Use a custom test renderer instead of default testing-library functions

* Add custom query for selecting tools

* move files around

Co-authored-by: David Luzar <luzar.david@gmail.com>

package.json

@@ -16,6 +16,8 @@
   },
   "description": "",
   "devDependencies": {
+    "@testing-library/jest-dom": "5.1.1",
+    "@testing-library/react": "9.4.0",
     "@types/jest": "25.1.2",
     "@types/nanoid": "2.1.0",
     "@types/react": "16.9.19",
@@ -24,12 +26,18 @@
     "eslint-config-prettier": "6.10.0",
     "eslint-plugin-prettier": "3.1.2",
     "husky": "4.2.1",
+    "jest-canvas-mock": "2.2.0",
     "lint-staged": "10.0.7",
     "node-sass": "4.13.1",
     "prettier": "1.19.1",
     "rewire": "4.0.1",
     "typescript": "3.7.5"
   },
+  "jest": {
+    "transformIgnorePatterns": [
+      "node_modules/(?!(roughjs|browser-nativefs)/)"
+    ]
+  },
   "eslintConfig": {
     "extends": [
       "prettier",