Add visual diffing in CI

8 files changed, 823 insertions, 171 deletions

diff --git a/.eslintrc.json b/.eslintrc.json
index 756acbda..b5328f41 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -5,7 +5,7 @@
         "plugin:jsonc/recommended-with-json"
     ],
     "parserOptions": {
-        "ecmaVersion": 8,
+        "ecmaVersion": 9,
         "sourceType": "script",
         "ecmaFeatures": {
             "globalReturn": false,
@@ -14,7 +14,7 @@
     },
     "env": {
         "browser": true,
-        "es2017": true,
+        "es2018": true,
         "webextensions": true
     },
     "plugins": [
@@ -27,12 +27,24 @@
         "/ext/lib/"
     ],
     "rules": {
-        "arrow-parens": ["error", "always"],
-        "comma-dangle": ["error", "never"],
-        "curly": ["error", "all"],
+        "arrow-parens": [
+            "error",
+            "always"
+        ],
+        "comma-dangle": [
+            "error",
+            "never"
+        ],
+        "curly": [
+            "error",
+            "all"
+        ],
         "dot-notation": "error",
         "eqeqeq": "error",
-        "func-names": ["error", "always"],
+        "func-names": [
+            "error",
+            "always"
+        ],
         "guard-for-in": "error",
         "new-parens": "error",
         "no-case-declarations": "error",
@@ -41,57 +53,184 @@
         "no-global-assign": "error",
         "no-param-reassign": "off",
         "no-prototype-builtins": "error",
-        "no-shadow": ["error", {"builtinGlobals": false}],
+        "no-shadow": [
+            "error",
+            {
+                "builtinGlobals": false
+            }
+        ],
         "no-undef": "error",
         "no-undefined": "error",
-        "no-underscore-dangle": ["error", {"allowAfterThis": true, "allowAfterSuper": false, "allowAfterThisConstructor": false}],
+        "no-underscore-dangle": [
+            "error",
+            {
+                "allowAfterThis": true,
+                "allowAfterSuper": false,
+                "allowAfterThisConstructor": false
+            }
+        ],
         "no-unexpected-multiline": "error",
         "no-unneeded-ternary": "error",
-        "no-unused-vars": ["error", {"vars": "local", "args": "after-used", "argsIgnorePattern": "^_", "caughtErrors": "none"}],
+        "no-unused-vars": [
+            "error",
+            {
+                "vars": "local",
+                "args": "after-used",
+                "argsIgnorePattern": "^_",
+                "caughtErrors": "none"
+            }
+        ],
         "no-unused-expressions": "error",
         "no-var": "error",
-        "prefer-const": ["error", {"destructuring": "all"}],
-        "quote-props": ["error", "consistent"],
-        "quotes": ["error", "single", "avoid-escape"],
+        "prefer-const": [
+            "error",
+            {
+                "destructuring": "all"
+            }
+        ],
+        "quote-props": [
+            "error",
+            "consistent"
+        ],
+        "quotes": [
+            "error",
+            "single",
+            "avoid-escape"
+        ],
         "require-atomic-updates": "off",
         "semi": "error",
-        "wrap-iife": ["error", "inside"],
-
-        "brace-style": ["error", "1tbs", {"allowSingleLine": true}],
-        "indent": ["error", 4, {"SwitchCase": 1, "MemberExpression": 1, "flatTernaryExpressions": true, "ignoredNodes": ["ConditionalExpression"]}],
+        "wrap-iife": [
+            "error",
+            "inside"
+        ],
+        "brace-style": [
+            "error",
+            "1tbs",
+            {
+                "allowSingleLine": true
+            }
+        ],
+        "indent": [
+            "error",
+            4,
+            {
+                "SwitchCase": 1,
+                "MemberExpression": 1,
+                "flatTernaryExpressions": true,
+                "ignoredNodes": [
+                    "ConditionalExpression"
+                ]
+            }
+        ],
         "object-curly-newline": "error",
-        "padded-blocks": ["error", "never"],
-
-        "array-bracket-spacing": ["error", "never"],
-        "arrow-spacing": ["error", {"before": true, "after": true}],
-        "block-spacing": ["error", "always"],
-        "comma-spacing": ["error", {"before": false, "after": true}],
-        "computed-property-spacing": ["error", "never"],
-        "func-call-spacing": ["error", "never"],
-        "function-paren-newline": ["error", "multiline-arguments"],
-        "generator-star-spacing": ["error", "before"],
-        "key-spacing": ["error", {"beforeColon": false, "afterColon": true, "mode": "strict"}],
-        "keyword-spacing": ["error", {"before": true, "after": true}],
+        "padded-blocks": [
+            "error",
+            "never"
+        ],
+        "array-bracket-spacing": [
+            "error",
+            "never"
+        ],
+        "arrow-spacing": [
+            "error",
+            {
+                "before": true,
+                "after": true
+            }
+        ],
+        "block-spacing": [
+            "error",
+            "always"
+        ],
+        "comma-spacing": [
+            "error",
+            {
+                "before": false,
+                "after": true
+            }
+        ],
+        "computed-property-spacing": [
+            "error",
+            "never"
+        ],
+        "func-call-spacing": [
+            "error",
+            "never"
+        ],
+        "function-paren-newline": [
+            "error",
+            "multiline-arguments"
+        ],
+        "generator-star-spacing": [
+            "error",
+            "before"
+        ],
+        "key-spacing": [
+            "error",
+            {
+                "beforeColon": false,
+                "afterColon": true,
+                "mode": "strict"
+            }
+        ],
+        "keyword-spacing": [
+            "error",
+            {
+                "before": true,
+                "after": true
+            }
+        ],
         "no-trailing-spaces": "error",
         "no-whitespace-before-property": "error",
-        "object-curly-spacing": ["error", "never"],
-        "rest-spread-spacing": ["error", "never"],
-        "semi-spacing": ["error", {"before": false, "after": true}],
-        "space-before-function-paren": ["error", {
-            "anonymous": "never",
-            "named": "never",
-            "asyncArrow": "always"
-        }],
-        "space-in-parens": ["error", "never"],
+        "object-curly-spacing": [
+            "error",
+            "never"
+        ],
+        "rest-spread-spacing": [
+            "error",
+            "never"
+        ],
+        "semi-spacing": [
+            "error",
+            {
+                "before": false,
+                "after": true
+            }
+        ],
+        "space-before-function-paren": [
+            "error",
+            {
+                "anonymous": "never",
+                "named": "never",
+                "asyncArrow": "always"
+            }
+        ],
+        "space-in-parens": [
+            "error",
+            "never"
+        ],
         "space-unary-ops": "error",
-        "spaced-comment": ["error", "always"],
-        "switch-colon-spacing": ["error", {"after": true, "before": false}],
-        "template-curly-spacing": ["error", "never"],
-        "template-tag-spacing": ["error", "never"],
-
+        "spaced-comment": [
+            "error",
+            "always"
+        ],
+        "switch-colon-spacing": [
+            "error",
+            {
+                "after": true,
+                "before": false
+            }
+        ],
+        "template-curly-spacing": [
+            "error",
+            "never"
+        ],
+        "template-tag-spacing": [
+            "error",
+            "never"
+        ],
         "no-unsanitized/method": "error",
         "no-unsanitized/property": "error",
-
         "jsdoc/check-access": "error",
         "jsdoc/check-alignment": "error",
         "jsdoc/check-line-alignment": "error",
@@ -103,11 +242,17 @@
         "jsdoc/empty-tags": "error",
         "jsdoc/implements-on-classes": "error",
         "jsdoc/multiline-blocks": "error",
-        "jsdoc/newline-after-description": ["error", "never"],
+        "jsdoc/newline-after-description": [
+            "error",
+            "never"
+        ],
         "jsdoc/no-bad-blocks": "error",
         "jsdoc/no-multi-asterisks": "error",
         "jsdoc/require-asterisk-prefix": "error",
-        "jsdoc/require-hyphen-before-param-description": ["error", "never"],
+        "jsdoc/require-hyphen-before-param-description": [
+            "error",
+            "never"
+        ],
         "jsdoc/require-jsdoc": "off",
         "jsdoc/require-param": "error",
         "jsdoc/require-param-description": "error",
@@ -126,17 +271,51 @@
         "jsdoc/require-yields-check": "error",
         "jsdoc/tag-lines": "error",
         "jsdoc/valid-types": "error",
-
-        "jsonc/indent": ["error", 4],
-        "jsonc/array-bracket-newline": ["error", "consistent"],
-        "jsonc/array-bracket-spacing": ["error", "never"],
-        "jsonc/array-element-newline": ["error", "consistent"],
-        "jsonc/comma-style": ["error", "last"],
-        "jsonc/key-spacing": ["error", {"beforeColon": false, "afterColon": true, "mode": "strict"}],
+        "jsonc/indent": [
+            "error",
+            4
+        ],
+        "jsonc/array-bracket-newline": [
+            "error",
+            "consistent"
+        ],
+        "jsonc/array-bracket-spacing": [
+            "error",
+            "never"
+        ],
+        "jsonc/array-element-newline": [
+            "error",
+            "consistent"
+        ],
+        "jsonc/comma-style": [
+            "error",
+            "last"
+        ],
+        "jsonc/key-spacing": [
+            "error",
+            {
+                "beforeColon": false,
+                "afterColon": true,
+                "mode": "strict"
+            }
+        ],
         "jsonc/no-octal-escape": "error",
-        "jsonc/object-curly-newline": ["error", {"consistent": true}],
-        "jsonc/object-curly-spacing": ["error", "never"],
-        "jsonc/object-property-newline": ["error", {"allowAllPropertiesOnSameLine": true}]
+        "jsonc/object-curly-newline": [
+            "error",
+            {
+                "consistent": true
+            }
+        ],
+        "jsonc/object-curly-spacing": [
+            "error",
+            "never"
+        ],
+        "jsonc/object-property-newline": [
+            "error",
+            {
+                "allowAllPropertiesOnSameLine": true
+            }
+        ]
     },
     "overrides": [
         {
@@ -152,7 +331,10 @@
                 "test/data/translator-test-results.json"
             ],
             "rules": {
-                "jsonc/indent": ["error", 2]
+                "jsonc/indent": [
+                    "error",
+                    2
+                ]
             }
         },
         {
@@ -160,8 +342,12 @@
                 "test/data/dictionaries/valid-dictionary1/term_bank_1.json"
             ],
             "rules": {
-                "jsonc/array-element-newline": ["off"],
-                "jsonc/object-property-newline": ["off"]
+                "jsonc/array-element-newline": [
+                    "off"
+                ],
+                "jsonc/object-property-newline": [
+                    "off"
+                ]
             }
         },
         {
@@ -188,7 +374,9 @@
             }
         },
         {
-            "files": ["ext/**/*.js"],
+            "files": [
+                "ext/**/*.js"
+            ],
             "excludedFiles": [
                 "ext/js/core.js",
                 "ext/js/accessibility/google-docs.js",
@@ -215,7 +403,9 @@
             }
         },
         {
-            "files": ["ext/**/*.js"],
+            "files": [
+                "ext/**/*.js"
+            ],
             "excludedFiles": [
                 "ext/js/core.js",
                 "ext/js/accessibility/google-docs.js",
@@ -227,7 +417,9 @@
             }
         },
         {
-            "files": ["ext/js/yomichan.js"],
+            "files": [
+                "ext/js/yomichan.js"
+            ],
             "globals": {
                 "chrome": "writable"
             }
@@ -237,7 +429,9 @@
                 "test/**/*.js",
                 "dev/**/*.js"
             ],
-            "excludedFiles": ["test/data/html/*.js"],
+            "excludedFiles": [
+                "test/data/html/*.js"
+            ],
             "parserOptions": {
                 "ecmaVersion": 8,
                 "sourceType": "module"
@@ -251,6 +445,35 @@
         },
         {
             "files": [
+                "playwright.config.js"
+            ],
+            "env": {
+                "browser": false,
+                "es2017": true,
+                "node": true,
+                "webextensions": false
+            },
+            "rules": {
+                "no-undefined": "off"
+            }
+        },
+        {
+            "files": [
+                "visual.spec.js"
+            ],
+            "env": {
+                "browser": false,
+                "es2017": true,
+                "node": true,
+                "webextensions": false
+            },
+            "rules": {
+                "no-undefined": "off",
+                "no-empty-pattern": "off"
+            }
+        },
+        {
+            "files": [
                 "ext/js/core.js",
                 "ext/js/yomichan.js",
                 "ext/js/accessibility/accessibility-controller.js",
diff --git a/.github/workflows/playwright.yml b/.github/workflows/playwright.yml
new file mode 100644
index 00000000..5ee786ef
--- /dev/null
+++ b/.github/workflows/playwright.yml
@@ -0,0 +1,109 @@
+name: Playwright Tests
+on:
+  push:
+    branches: [master]
+  pull_request:
+permissions:
+  contents: read
+jobs:
+  playwright:
+    timeout-minutes: 60
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+      contents: write
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: actions/setup-node@v3
+        with:
+          cache: "npm"
+          node-version-file: ".node-version"
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Cache playwright browsers
+        id: cache-playwright
+        uses: actions/cache@v3
+        with:
+          path: |
+            ~/.cache/ms-playwright
+          key: cache-playwright-${{ hashFiles('package-lock.json') }} # playwright version is included in package-lock, so this serves as a reasonable cache key
+
+      - if: ${{ steps.cache-playwright.outputs.cache-hit != 'true' }}
+        name: Install Playwright Browsers
+        run: npx playwright install --with-deps chromium
+
+      - name: Grab latest dictionaries from dictionaries branch
+        uses: actions/checkout@v3
+        with:
+          ref: dictionaries
+          path: dictionaries
+
+      - name: Grab latest screenshots from master branch
+        uses: dawidd6/action-download-artifact@5e780fc7bbd0cac69fc73271ed86edf5dcb72d67 # pin@v2
+        continue-on-error: true
+        id: download-screenshots
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          name: playwright-screenshots
+          branch: master
+          workflow: playwright.yml
+          workflow_conclusion: success
+          path: test/playwright/__screenshots__/
+
+      - name: "[PR] Generate new screenshots & compare against master"
+        id: playwright
+        run: |
+          EOF=$(dd if=/dev/urandom bs=15 count=1 status=none | base64)
+          echo "PLAYWRIGHT_OUTPUT<<$EOF" >> $GITHUB_OUTPUT
+          npx playwright test 2>&1 | tee $GITHUB_OUTPUT || true
+          echo "$EOF" >> $GITHUB_OUTPUT
+          echo "NUM_FAILED=$(grep -c 'Screenshot comparison failed' $GITHUB_OUTPUT)" >> $GITHUB_OUTPUT
+        continue-on-error: true
+        if: github.event_name == 'pull_request' && steps.download-screenshots.outcome != 'failure'
+
+      - name: "[Push] Generate new authoritative screenshots for master"
+        id: playwright-master
+        run: npx playwright test -u
+        if: github.event_name == 'push'
+
+      - uses: actions/upload-artifact@v3
+        with:
+          name: playwright-screenshots
+          path: test/playwright/__screenshots__/
+
+      - uses: actions/upload-artifact@v3
+        with:
+          name: playwright-report
+          path: playwright-report/
+
+      - name: "[Couldn't download screenshots] Comment results on PR"
+        uses: mshick/add-pr-comment@a65df5f64fc741e91c59b8359a4bc56e57aaf5b1 # pin@v2
+        if: github.event_name == 'pull_request' && steps.download-screenshots.outcome == 'failure'
+        with:
+          message: |
+            :heavy_exclamation_mark: Could not fetch screenshots from master branch, so had nothing to make a visual comparison against; please check the "download-screenshots" step in the workflow run and rerun it before merging.
+
+      - name: "[Success] Comment results on PR"
+        uses: mshick/add-pr-comment@a65df5f64fc741e91c59b8359a4bc56e57aaf5b1 # pin@v2
+        if: github.event_name == 'pull_request' && steps.download-screenshots.outcome != 'failure' && steps.playwright.outputs.NUM_FAILED == 0
+        with:
+          message: |
+            :heavy_check_mark: No visual differences introduced by this PR.
+            [View Playwright Report](${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}#artifacts) (note: open the "playwright-report" artifact)
+
+      - name: "[Failure] Comment results on PR"
+        uses: mshick/add-pr-comment@a65df5f64fc741e91c59b8359a4bc56e57aaf5b1 # pin@v2
+        if: github.event_name == 'pull_request' && steps.download-screenshots.outcome != 'failure' && steps.playwright.outputs.NUM_FAILED != 0
+        with:
+          message: |
+            :warning: {{ steps.playwright.outputs.NUM_FAILED }} visual differences introduced by this PR; please validate if they are desirable.
+            <details>
+            <summary>Playwright Test Results</summary>
+            <pre>
+            ${{ steps.playwright.outputs.PLAYWRIGHT_OUTPUT }}
+            </pre>
+            </details>
+            [View Playwright Report](${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}#artifacts) (note: open the "playwright-report" artifact)
diff --git a/.gitignore b/.gitignore
index ab07d570..d4e5da07 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,8 @@
 node_modules/
 builds/
 .DS_Store
+dictionaries/
+/test-results/
+/playwright-report/
+/playwright/.cache/
+/test/playwright/__screenshots__/
diff --git a/package-lock.json b/package-lock.json
index 5dd54bc6..4878437a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,15 +1,16 @@
 {
-    "name": "yomichan",
+    "name": "yomitan",
     "version": "0.0.0",
     "lockfileVersion": 2,
     "requires": true,
     "packages": {
         "": {
-            "name": "yomichan",
+            "name": "yomitan",
             "version": "0.0.0",
             "hasInstallScript": true,
             "license": "GPL-3.0-or-later",
             "devDependencies": {
+                "@playwright/test": "^1.31.2",
                 "ajv": "^8.11.0",
                 "browserify": "^17.0.0",
                 "css": "^3.0.0",
@@ -332,6 +333,25 @@
                 "node": ">= 8"
             }
         },
+        "node_modules/@playwright/test": {
+            "version": "1.31.2",
+            "resolved": "https://registry.npmjs.org/@playwright/test/-/test-1.31.2.tgz",
+            "integrity": "sha512-BYVutxDI4JeZKV1+ups6dt5WiqKhjBtIYowyZIJ3kBDmJgsuPKsqqKNIMFbUePLSCmp2cZu+BDL427RcNKTRYw==",
+            "dev": true,
+            "dependencies": {
+                "@types/node": "*",
+                "playwright-core": "1.31.2"
+            },
+            "bin": {
+                "playwright": "cli.js"
+            },
+            "engines": {
+                "node": ">=14"
+            },
+            "optionalDependencies": {
+                "fsevents": "2.3.2"
+            }
+        },
         "node_modules/@pnpm/network.ca-file": {
             "version": "1.0.1",
             "resolved": "https://registry.npmjs.org/@pnpm/network.ca-file/-/network.ca-file-1.0.1.tgz",
@@ -3474,6 +3494,20 @@
             "integrity": "sha1-FQStJSMVjKpA20onh8sBQRmU6k8=",
             "dev": true
         },
+        "node_modules/fsevents": {
+            "version": "2.3.2",
+            "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-2.3.2.tgz",
+            "integrity": "sha512-xiqMQR4xAeHTuB9uWm+fFRcIOgKBMiOBP+eXiyT7jsgVCq1bkVygt00oASowB7EdtpOHaaPgKt812P9ab+DDKA==",
+            "dev": true,
+            "hasInstallScript": true,
+            "optional": true,
+            "os": [
+                "darwin"
+            ],
+            "engines": {
+                "node": "^8.16.0 || ^10.6.0 || >=11.0.0"
+            }
+        },
         "node_modules/function-bind": {
             "version": "1.1.1",
             "resolved": "https://registry.npmjs.org/function-bind/-/function-bind-1.1.1.tgz",
@@ -6409,6 +6443,18 @@
             "integrity": "sha512-mMMOwSKrmyl+Y12Ri2xhH1lbzQxwwpuru9VjyJpgFIH4asSj88F2csdMwN6+M5g1Ll4rmsYghHLQJw81tgZ7LQ==",
             "dev": true
         },
+        "node_modules/playwright-core": {
+            "version": "1.31.2",
+            "resolved": "https://registry.npmjs.org/playwright-core/-/playwright-core-1.31.2.tgz",
+            "integrity": "sha512-a1dFgCNQw4vCsG7bnojZjDnPewZcw7tZUNFN0ZkcLYKj+mPmXvg4MpaaKZ5SgqPsOmqIf2YsVRkgqiRDxD+fDQ==",
+            "dev": true,
+            "bin": {
+                "playwright": "cli.js"
+            },
+            "engines": {
+                "node": ">=14"
+            }
+        },
         "node_modules/postcss": {
             "version": "8.4.18",
             "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.18.tgz",
@@ -9389,6 +9435,17 @@
                 "fastq": "^1.6.0"
             }
         },
+        "@playwright/test": {
+            "version": "1.31.2",
+            "resolved": "https://registry.npmjs.org/@playwright/test/-/test-1.31.2.tgz",
+            "integrity": "sha512-BYVutxDI4JeZKV1+ups6dt5WiqKhjBtIYowyZIJ3kBDmJgsuPKsqqKNIMFbUePLSCmp2cZu+BDL427RcNKTRYw==",
+            "dev": true,
+            "requires": {
+                "@types/node": "*",
+                "fsevents": "2.3.2",
+                "playwright-core": "1.31.2"
+            }
+        },
         "@pnpm/network.ca-file": {
             "version": "1.0.1",
             "resolved": "https://registry.npmjs.org/@pnpm/network.ca-file/-/network.ca-file-1.0.1.tgz",
@@ -11834,6 +11891,13 @@
             "integrity": "sha1-FQStJSMVjKpA20onh8sBQRmU6k8=",
             "dev": true
         },
+        "fsevents": {
+            "version": "2.3.2",
+            "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-2.3.2.tgz",
+            "integrity": "sha512-xiqMQR4xAeHTuB9uWm+fFRcIOgKBMiOBP+eXiyT7jsgVCq1bkVygt00oASowB7EdtpOHaaPgKt812P9ab+DDKA==",
+            "dev": true,
+            "optional": true
+        },
         "function-bind": {
             "version": "1.1.1",
             "resolved": "https://registry.npmjs.org/function-bind/-/function-bind-1.1.1.tgz",
@@ -14049,6 +14113,12 @@
             "integrity": "sha512-mMMOwSKrmyl+Y12Ri2xhH1lbzQxwwpuru9VjyJpgFIH4asSj88F2csdMwN6+M5g1Ll4rmsYghHLQJw81tgZ7LQ==",
             "dev": true
         },
+        "playwright-core": {
+            "version": "1.31.2",
+            "resolved": "https://registry.npmjs.org/playwright-core/-/playwright-core-1.31.2.tgz",
+            "integrity": "sha512-a1dFgCNQw4vCsG7bnojZjDnPewZcw7tZUNFN0ZkcLYKj+mPmXvg4MpaaKZ5SgqPsOmqIf2YsVRkgqiRDxD+fDQ==",
+            "dev": true
+        },
         "postcss": {
             "version": "8.4.18",
             "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.18.tgz",
diff --git a/package.json b/package.json
index 6ec3eecf..2de7bcef 100644
--- a/package.json
+++ b/package.json
@@ -36,6 +36,7 @@
         "sourceDir": "ext"
     },
     "devDependencies": {
+        "@playwright/test": "^1.31.2",
         "ajv": "^8.11.0",
         "browserify": "^17.0.0",
         "css": "^3.0.0",
diff --git a/playwright.config.js b/playwright.config.js
new file mode 100644
index 00000000..0f15ff59
--- /dev/null
+++ b/playwright.config.js
@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2023  Yomitan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+// @ts-check
+const {defineConfig, devices} = require('@playwright/test');
+
+/**
+ * Read environment variables from file.
+ * https://github.com/motdotla/dotenv
+ */
+// require('dotenv').config();
+
+/**
+ * @see https://playwright.dev/docs/test-configuration
+ */
+module.exports = defineConfig({
+    testDir: './test/playwright',
+    snapshotPathTemplate: '{testDir}/__screenshots__/{testFilePath}/{arg}{ext}',
+    /* Maximum time one test can run for. */
+    timeout: 60 * 60 * 1000,
+    expect: {
+        /**
+         * Maximum time expect() should wait for the condition to be met.
+         * For example in `await expect(locator).toHaveText();`
+         */
+        timeout: 5000
+    },
+    /* Run tests in files in parallel */
+    fullyParallel: true,
+    /* Fail the build on CI if you accidentally left test.only in the source code. */
+    forbidOnly: !!process.env.CI,
+    /* Retry on CI only */
+    retries: process.env.CI ? 2 : 0,
+    /* Opt out of parallel tests on CI. */
+    workers: process.env.CI ? 1 : undefined,
+    /* Reporter to use. See https://playwright.dev/docs/test-reporters */
+    reporter: 'html',
+    /* Shared settings for all the projects below. See https://playwright.dev/docs/api/class-testoptions. */
+    use: {
+        /* Maximum time each action such as `click()` can take. Defaults to 0 (no limit). */
+        actionTimeout: 60 * 1000,
+        /* Base URL to use in actions like `await page.goto('/')`. */
+        // baseURL: 'http://localhost:3000',
+
+        /* Collect trace when retrying the failed test. See https://playwright.dev/docs/trace-viewer */
+        trace: 'on-first-retry'
+    },
+
+    /* Configure projects for major browsers */
+    projects: [
+        {
+            name: 'chromium',
+            use: {...devices['Desktop Chrome']}
+        }
+
+        // {
+        //   name: 'firefox',
+        //   use: { ...devices['Desktop Firefox'] },
+        // },
+
+        // {
+        //   name: 'webkit',
+        //   use: { ...devices['Desktop Safari'] },
+        // },
+
+        /* Test against mobile viewports. */
+        // {
+        //   name: 'Mobile Chrome',
+        //   use: { ...devices['Pixel 5'] },
+        // },
+        // {
+        //   name: 'Mobile Safari',
+        //   use: { ...devices['iPhone 12'] },
+        // },
+
+        /* Test against branded browsers. */
+        // {
+        //   name: 'Microsoft Edge',
+        //   use: { channel: 'msedge' },
+        // },
+        // {
+        //   name: 'Google Chrome',
+        //   use: { channel: 'chrome' },
+        // },
+    ]
+
+    /* Folder for test artifacts such as screenshots, videos, traces, etc. */
+    // outputDir: 'test-results/',
+
+    /* Run your local dev server before starting the tests */
+    // webServer: {
+    //   command: 'npm run start',
+    //   port: 3000,
+    // },
+});
+
diff --git a/test/data/html/test-document2.html b/test/data/html/test-document2.html
index fb3adb59..399c3bd8 100644
--- a/test/data/html/test-document2.html
+++ b/test/data/html/test-document2.html
@@ -1,34 +1,40 @@
 <!DOCTYPE html>
 <html>
-    <head>
-        <meta charset="UTF-8">
-        <meta name="viewport" content="width=device-width,initial-scale=1">
-        <title>Yomichan Manual Tests</title>
-        <link rel="icon" type="image/gif" href="data:image/gif;base64,R0lGODlhEAAQAKEBAAAAAP///////////yH5BAEKAAIALAAAAAAQABAAAAImFI6Zpt0B4YkS0TCpq07xbmEgcGVRUpLaI46ZG7ppalY0jDCwUAAAOw==">
-        <link rel="stylesheet" href="test-stylesheet.css">
-        <script src="test-document2-script.js"></script>
-    </head>
-    <style id="container-styles">
-.container {
-    width: 100%;
-    height: 200px;
-    border: 1px solid #d8d8d8;
-    position: relative;
-    box-sizing: border-box;
-}
-.container-inner {
-    background-color: #f8f8f8;
-    padding: 0.5em;
-    position: absolute;
-    left: 0;
-    top: 0;
-    bottom: 0;
-    right: 0;
-}
-.danger {
-    color: #c83c28;
-}
-    </style>
+
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width,initial-scale=1">
+    <title>Yomichan Manual Tests</title>
+    <link rel="icon" type="image/gif"
+        href="data:image/gif;base64,R0lGODlhEAAQAKEBAAAAAP///////////yH5BAEKAAIALAAAAAAQABAAAAImFI6Zpt0B4YkS0TCpq07xbmEgcGVRUpLaI46ZG7ppalY0jDCwUAAAOw==">
+    <link rel="stylesheet" href="test-stylesheet.css">
+    <script src="test-document2-script.js"></script>
+</head>
+<style id="container-styles">
+    .container {
+        width: 100%;
+        height: 200px;
+        border: 1px solid #d8d8d8;
+        position: relative;
+        box-sizing: border-box;
+    }
+
+    .container-inner {
+        background-color: #f8f8f8;
+        padding: 0.5em;
+        position: absolute;
+        left: 0;
+        top: 0;
+        bottom: 0;
+        right: 0;
+    }
+
+    .danger {
+        color: #c83c28;
+    }
+
+</style>
+
 <body>
 
     <h1>Yomichan Manual Tests</h1>
@@ -36,56 +42,62 @@
 
     <y-test>
         <y-description>Standard content.</y-description>
-        <div class="fullscreen-element container"><div class="container-inner">
-            <div>
-                ありがとう
-            </div>
-            <div>
-                <a href="#" class="fullscreen-link">Toggle fullscreen</a>
+        <div class="fullscreen-element container hovertarget">
+            <div class="container-inner">
+                <div>
+                    ありがとう
+                </div>
+                <div>
+                    <a href="#" class="fullscreen-link">Toggle fullscreen</a>
+                </div>
             </div>
-        </div></div>
+        </div>
     </y-test>
 
     <y-test data-shadow-mode="open">
         <y-description>Content inside of an open shadow DOM.</y-description>
-        <div class="template-content-container"></div>
+        <div class="template-content-container hovertarget"></div>
         <template>
             <link rel="stylesheet" href="test-stylesheet.css">
-            <div class="fullscreen-element container"><div class="container-inner">
-                <div>
-                    ありがとう
-                </div>
-                <div>
-                    <a href="#" class="fullscreen-link">Toggle fullscreen</a>
+            <div class="fullscreen-element container">
+                <div class="container-inner">
+                    <div>
+                        ありがとう
+                    </div>
+                    <div>
+                        <a href="#" class="fullscreen-link">Toggle fullscreen</a>
+                    </div>
                 </div>
-            </div></div>
+            </div>
         </template>
     </y-test>
 
     <y-test data-shadow-mode="closed">
         <y-description>Content inside of a closed shadow DOM.</y-description>
-        <div class="template-content-container"></div>
+        <div class="template-content-container hovertarget"></div>
         <template>
             <link rel="stylesheet" href="test-stylesheet.css">
-            <div class="fullscreen-element container"><div class="container-inner">
-                <div>
-                    ありがとう
+            <div class="fullscreen-element container">
+                <div class="container-inner">
+                    <div>
+                        ありがとう
+                    </div>
+                    <div>
+                        <a href="#" class="fullscreen-link">Toggle fullscreen</a>
+                    </div>
                 </div>
-                <div>
-                    <a href="#" class="fullscreen-link">Toggle fullscreen</a>
-                </div>
-            </div></div>
+            </div>
         </template>
     </y-test>
 
     <y-test>
         <y-description>&lt;iframe&gt; element.</y-description>
-        <iframe src="test-document2-frame1.html" allowfullscreen="true" class="container"></iframe>
+        <iframe src="test-document2-frame1.html" allowfullscreen="true" class="container hovertarget"></iframe>
     </y-test>
 
     <y-test data-shadow-mode="open">
         <y-description>&lt;iframe&gt; element inside of an open shadow DOM.</y-description>
-        <div class="template-content-container"></div>
+        <div class="template-content-container hovertarget"></div>
         <template>
             <iframe src="test-document2-frame1.html" allowfullscreen="true" class="container"></iframe>
         </template>
@@ -93,7 +105,7 @@
 
     <y-test data-shadow-mode="closed">
         <y-description>&lt;iframe&gt; element inside of a closed shadow DOM.</y-description>
-        <div class="template-content-container"></div>
+        <div class="template-content-container hovertarget"></div>
         <template>
             <iframe src="test-document2-frame1.html" allowfullscreen="true" class="container"></iframe>
         </template>
@@ -101,22 +113,26 @@
 
     <y-test>
         <y-description>&lt;iframe&gt; element with data URL.</y-description>
-        <iframe id="iframe-with-data-url" src="data:text/html;base64,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" allowfullscreen="true" class="container"></iframe>
+        <iframe id="iframe-with-data-url"
+            src="data:text/html;base64,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"
+            allowfullscreen="true" class="container hovertarget"></iframe>
     </y-test>
 
     <y-test>
         <y-description>&lt;iframe&gt; element with blob URL.</y-description>
-        <iframe id="iframe-with-blob-url" allowfullscreen="true" class="container"></iframe>
+        <iframe id="iframe-with-blob-url" allowfullscreen="true" class="container hovertarget"></iframe>
     </y-test>
 
     <y-test>
         <y-description>&lt;iframe&gt; element with srcdoc.</y-description>
-        <iframe allowfullscreen="true" class="iframe-with-srcdoc container"></iframe>
+        <iframe allowfullscreen="true" class="iframe-with-srcdoc container hovertarget"></iframe>
     </y-test>
 
     <y-test>
-        <y-description>&lt;iframe&gt; element with srcdoc and <code>sandbox="allow-same-origin allow-scripts"</code>.</y-description>
-        <iframe allowfullscreen="true" class="iframe-with-srcdoc container" sandbox="allow-same-origin allow-scripts"></iframe>
+        <y-description>&lt;iframe&gt; element with srcdoc and
+            <code>sandbox="allow-same-origin allow-scripts"</code>.</y-description>
+        <iframe allowfullscreen="true" class="iframe-with-srcdoc container hovertarget"
+            sandbox="allow-same-origin allow-scripts"></iframe>
     </y-test>
 
     <y-test>
@@ -124,41 +140,39 @@
             &lt;iframe&gt; element with srcdoc and <code>sandbox="allow-scripts"</code>.<br>
             <span class="danger">This element is expected to not work.</span>
         </y-description>
-        <iframe allowfullscreen="true" class="iframe-with-srcdoc container" sandbox="allow-scripts"></iframe>
+        <iframe allowfullscreen="true" class="iframe-with-srcdoc container hovertarget"
+            sandbox="allow-scripts"></iframe>
     </y-test>
 
     <y-test>
         <y-description>SVG &lt;img&gt;.</y-description>
-        <img src="test-document2-frame2.svg" class="container" alt="">
+        <img src="test-document2-frame2.svg" class="container hovertarget" alt="">
     </y-test>
 
     <y-test>
         <y-description>SVG &lt;object&gt;.</y-description>
-        <object data="test-document2-frame2.svg" type="image/svg+xml" class="container"></object>
+        <object data="test-document2-frame2.svg" type="image/svg+xml" class="container hovertarget"></object>
     </y-test>
 
     <y-test>
         <y-description>SVG &lt;embed&gt;.</y-description>
-        <embed type="image/svg+xml" src="test-document2-frame2.svg" class="container">
+        <embed type="image/svg+xml" src="test-document2-frame2.svg" class="container hovertarget">
     </y-test>
 
     <y-test>
         <y-description>SVG &lt;iframe&gt;.</y-description>
-        <iframe src="test-document2-frame2.svg" allowfullscreen="true" class="container"></iframe>
+        <iframe src="test-document2-frame2.svg" allowfullscreen="true" class="container hovertarget"></iframe>
     </y-test>
 
     <y-test>
         <y-description>SVG &lt;svg&gt;.</y-description>
-        <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" class="container" style="background-color: #f8f8f8;" focusable="false">
-            <text
-                x="7"
-                y="12"
-                style="
+        <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" class="container hovertarget"
+            style="background-color: #f8f8f8;" focusable="false">
+            <text x="7" y="12" style="
                 font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
                 font-size: 14px;
                 fill: #000000;
-                dominant-baseline: hanging;"
-            >
+                dominant-baseline: hanging;">
                 ありがとう
             </text>
         </svg>
@@ -166,42 +180,43 @@
 
 
     <script>
-(() => {
-    function stringToTypedArray(string) {
-        const array = new Uint8Array(string.length);
-        for (let i = 0; i < string.length; ++i) {
-            array[i] = string.charCodeAt(i);
-        }
-        return array;
-    }
-
-    function dataUrlToContent(dataUrl) {
-        const [, type, isBase64, data] = /^data:([^;]*);(base64,)?([\w\W]*)$/.exec(dataUrl);
-        const content = (
-            isBase64 ?
-            new TextDecoder().decode(stringToTypedArray(atob(data))) :
-            data
-        );
-        return {content, type};
-    }
-
-    function dataUrlToBlob(dataUrl) {
-        const {content, type} = dataUrlToContent(dataUrl);
-        return new Blob([content], {type});
-    }
-
-    for (const element of document.querySelectorAll('y-test')) {
-        setup(element);
-    }
-
-    const iframeWithDataUrl = document.querySelector('#iframe-with-data-url');
-    const iframeWithBlobUrl = document.querySelector('#iframe-with-blob-url');
-    iframeWithBlobUrl.src = URL.createObjectURL(dataUrlToBlob(iframeWithDataUrl.src));
-    for (const iframeWithSrcdoc of document.querySelectorAll('.iframe-with-srcdoc')) {
-        iframeWithSrcdoc.srcdoc = dataUrlToContent(iframeWithDataUrl.src).content;
-    }
-})();
+        (() => {
+            function stringToTypedArray(string) {
+                const array = new Uint8Array(string.length);
+                for (let i = 0; i < string.length; ++i) {
+                    array[i] = string.charCodeAt(i);
+                }
+                return array;
+            }
+
+            function dataUrlToContent(dataUrl) {
+                const [, type, isBase64, data] = /^data:([^;]*);(base64,)?([\w\W]*)$/.exec(dataUrl);
+                const content = (
+                    isBase64 ?
+                        new TextDecoder().decode(stringToTypedArray(atob(data))) :
+                        data
+                );
+                return { content, type };
+            }
+
+            function dataUrlToBlob(dataUrl) {
+                const { content, type } = dataUrlToContent(dataUrl);
+                return new Blob([content], { type });
+            }
+
+            for (const element of document.querySelectorAll('y-test')) {
+                setup(element);
+            }
+
+            const iframeWithDataUrl = document.querySelector('#iframe-with-data-url');
+            const iframeWithBlobUrl = document.querySelector('#iframe-with-blob-url');
+            iframeWithBlobUrl.src = URL.createObjectURL(dataUrlToBlob(iframeWithDataUrl.src));
+            for (const iframeWithSrcdoc of document.querySelectorAll('.iframe-with-srcdoc')) {
+                iframeWithSrcdoc.srcdoc = dataUrlToContent(iframeWithDataUrl.src).content;
+            }
+        })();
     </script>
 
 </body>
+
 </html>
diff --git a/test/playwright/visual.spec.js b/test/playwright/visual.spec.js
new file mode 100644
index 00000000..acb12e97
--- /dev/null
+++ b/test/playwright/visual.spec.js
@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2023  Yomitan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+const path = require('path');
+const {test: base, chromium} = require('@playwright/test');
+const root = path.join(__dirname, '..', '..');
+
+export const test = base.extend({
+    context: async ({ }, use) => {
+        const pathToExtension = path.join(root, 'ext');
+        const context = await chromium.launchPersistentContext('', {
+            // headless: false,
+            args: [
+                '--headless=new',
+                `--disable-extensions-except=${pathToExtension}`,
+                `--load-extension=${pathToExtension}`
+            ]
+        });
+        await use(context);
+        await context.close();
+    },
+    extensionId: async ({context}, use) => {
+        let [background] = context.serviceWorkers();
+        if (!background) {
+            background = await context.waitForEvent('serviceworker');
+        }
+
+        const extensionId = background.url().split('/')[2];
+        await use(extensionId);
+    }
+});
+const expect = test.expect;
+
+test('visual', async ({context, page, extensionId}) => {
+    // wait for the on-install welcome.html tab to load, which becomes the foreground tab
+    const welcome = await context.waitForEvent('page');
+    welcome.close(); // close the welcome tab so our main tab becomes the foreground tab -- otherwise, the screenshot can hang
+
+    // open settings
+    await page.goto(`chrome-extension://${extensionId}/settings.html`);
+
+    await expect(page.locator('id=dictionaries')).toBeVisible();
+
+    // get the locator for the disk usage indicator so we can later mask it out of the screenshot
+    const storage_locator = page.locator('.storage-use-finite >> xpath=..');
+
+    // take a simple screenshot of the settings page
+    await expect.soft(page).toHaveScreenshot('settings-fresh.png', {mask: [storage_locator]});
+
+    // load in jmdict_english.zip
+    await page.locator('input[id="dictionary-import-file-input"]').setInputFiles(path.join(root, 'dictionaries/jmdict_english.zip'));
+    await expect(page.locator('id=dictionaries')).toHaveText('Dictionaries (1 installed, 1 enabled)', {timeout: 5 * 60 * 1000});
+
+    // take a screenshot of the settings page with jmdict loaded
+    await expect.soft(page).toHaveScreenshot('settings-jmdict-loaded.png', {mask: [storage_locator]});
+
+    const screenshot = async (doc_number, test_number, el, offset) => {
+        const test_name = 'doc' + doc_number + '-test' + test_number;
+
+        const box = await el.boundingBox();
+
+        // find the popup frame if it exists
+        let popup_frame = page.frames().find((f) => f.url().includes('popup.html'));
+
+        // otherwise prepare for it to be attached
+        let frame_attached;
+        if (popup_frame === undefined) {
+            frame_attached = page.waitForEvent('frameattached');
+        }
+        await page.mouse.move(box.x + offset.x, box.y + offset.y, {steps: 10}); // hover over the test
+        if (popup_frame === undefined) {
+            popup_frame = await frame_attached; // wait for popup to be attached
+        }
+        try {
+            await (await popup_frame.frameElement()).waitForElementState('visible', {timeout: 500});  // some tests don't have a popup, so don't fail if it's not there; TODO: check if the popup is expected to be there
+        } catch (error) {
+            console.log(test_name + ' has no popup');
+        }
+
+        await page.bringToFront(); // bring the page to the foreground so the screenshot doesn't hang; for some reason the frames result in page being in the background
+        await expect.soft(page).toHaveScreenshot(test_name + '.png');
+
+        await page.mouse.click(0, 0); // click away so popup disappears
+        await (await popup_frame.frameElement()).waitForElementState('hidden'); // wait for popup to disappear
+    };
+
+    // Load test-document1.html
+    await page.goto('file://' + path.join(root, 'test/data/html/test-document1.html'));
+    await page.setViewportSize({width: 1000, height: 1800});
+    await page.keyboard.down('Shift');
+    let i = 1;
+    for (const el of await page.locator('div > *:nth-child(1)').elementHandles()) {
+        await screenshot(1, i, el, {x: 6, y: 6});
+        i++;
+    }
+
+    // Load test-document2.html
+    await page.goto('file://' + path.join(root, 'test/data/html/test-document2.html'));
+    await page.setViewportSize({width: 1000, height: 4500});
+    await page.keyboard.down('Shift');
+    i = 1;
+    for (const el of await page.locator('.hovertarget').elementHandles()) {
+        await screenshot(2, i, el, {x: 15, y: 15});
+        i++;
+    }
+});