Merge pull request #228 from playwright-community/max-expects

feat: Add `max-expects` rule

README.md

@@ -118,8 +118,9 @@ command line option.\
 [suggestions](https://eslint.org/docs/latest/developer-guide/working-with-rules#providing-suggestions).
 
 | ✔  | 🔧  | 💡  | Rule                                                                                                                                                | Description                                                       |
-| :-: | :-: | :-: | --------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------- |
+| :-: | :-: | :-: | --------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------- | --- |
 | ✔  |     |     | [expect-expect](https://github.com/playwright-community/eslint-plugin-playwright/tree/main/docs/rules/expect-expect.md)                             | Enforce assertion to be made in a test body                       |
+| ✔  |     |     | [max-expects](https://github.com/playwright-community/eslint-plugin-playwright/tree/main/docs/rules/max-expects.md)                                 | Enforces a maximum number assertion calls in a test body          |     |
 | ✔  |     |     | [max-nested-describe](https://github.com/playwright-community/eslint-plugin-playwright/tree/main/docs/rules/max-nested-describe.md)                 | Enforces a maximum depth to nested describe calls                 |
 | ✔  | 🔧  |     | [missing-playwright-await](https://github.com/playwright-community/eslint-plugin-playwright/tree/main/docs/rules/missing-playwright-await.md)       | Enforce Playwright APIs to be awaited                             |
 |     |     |     | [no-commented-out-test](https://github.com/playwright-community/eslint-plugin-playwright/tree/main/docs/rules/no-commented-out-test.md)             | Disallow commented out tests                                      |

docs/rules/max-expects.md

@@ -0,0 +1,65 @@
+# Enforces a maximum number assertion calls in a test body (`max-expects`)
+
+As more assertions are made, there is a possible tendency for the test to be
+more likely to mix multiple objectives. To avoid this, this rule reports when
+the maximum number of assertions is exceeded.
+
+## Rule details
+
+This rule enforces a maximum number of `expect()` calls.
+
+The following patterns are considered warnings (with the default option of
+`{ "max": 5 } `):
+
+```js
+test('should not pass', () => {
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+});
+```
+
+The following patterns are **not** considered warnings (with the default option
+of `{ "max": 5 } `):
+
+```js
+test('shout pass');
+
+test('shout pass', () => {});
+
+test.skip('shout pass', () => {});
+
+test('should pass', function () {
+  expect(true).toBeDefined();
+});
+
+test('should pass', () => {
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+  expect(true).toBeDefined();
+});
+```
+
+## Options
+
+```json
+{
+  "playwright/max-expects": [
+    "error",
+    {
+      "max": 5
+    }
+  ]
+}
+```
+
+### `max`
+
+Enforces a maximum number of `expect()`.
+
+This has a default value of `5`.

src/index.ts

@@ -1,5 +1,6 @@
 import globals from 'globals';
 import expectExpect from './rules/expect-expect';
+import maxExpects from './rules/max-expects';
 import maxNestedDescribe from './rules/max-nested-describe';
 import missingPlaywrightAwait from './rules/missing-playwright-await';
 import noCommentedOutTests from './rules/no-commented-out-tests';
@@ -42,6 +43,7 @@ const index = {
   configs: {},
   rules: {
     'expect-expect': expectExpect,
+    'max-expects': maxExpects,
     'max-nested-describe': maxNestedDescribe,
     'missing-playwright-await': missingPlaywrightAwait,
     'no-commented-out-tests': noCommentedOutTests,

src/rules/max-expects.ts

@@ -0,0 +1,72 @@
+import { Rule } from 'eslint';
+import * as ESTree from 'estree';
+import { getExpectType, getParent, isTestCall } from '../utils/ast';
+
+export default {
+  create(context) {
+    const options = {
+      max: 5,
+      ...((context.options?.[0] as Record<string, unknown>) ?? {}),
+    };
+
+    let count = 0;
+
+    const maybeResetCount = (node: ESTree.Node) => {
+      const parent = getParent(node);
+      const isTestFn =
+        parent?.type !== 'CallExpression' || isTestCall(context, parent);
+
+      if (isTestFn) {
+        count = 0;
+      }
+    };
+
+    return {
+      ArrowFunctionExpression: maybeResetCount,
+      'ArrowFunctionExpression:exit': maybeResetCount,
+      CallExpression(node) {
+        if (!getExpectType(context, node)) return;
+
+        count += 1;
+
+        if (count > options.max) {
+          context.report({
+            data: {
+              count: count.toString(),
+              max: options.max.toString(),
+            },
+            messageId: 'exceededMaxAssertion',
+            node,
+          });
+        }
+      },
+      FunctionExpression: maybeResetCount,
+      'FunctionExpression:exit': maybeResetCount,
+    };
+  },
+  meta: {
+    docs: {
+      category: 'Best Practices',
+      description: 'Enforces a maximum number assertion calls in a test body',
+      recommended: false,
+      url: 'https://github.com/playwright-community/eslint-plugin-playwright/tree/main/docs/rules/max-expects.md',
+    },
+    messages: {
+      exceededMaxAssertion:
+        'Too many assertion calls ({{ count }}) - maximum allowed is {{ max }}',
+    },
+    schema: [
+      {
+        additionalProperties: false,
+        properties: {
+          max: {
+            minimum: 1,
+            type: 'integer',
+          },
+        },
+        type: 'object',
+      },
+    ],
+    type: 'suggestion',
+  },
+} as Rule.RuleModule;