refactor ♻️: improve code quality and test coverage

- Fix handling of missing groupOrder configuration
- Refactor negative conditions to positive ones with optional chaining
- Add comprehensive tests to achieve total coverage

src/css-rules/custom-order/__tests__/defaults.test.ts

@@ -0,0 +1,115 @@
+import tsParser from '@typescript-eslint/parser';
+import { run } from 'eslint-vitest-rule-tester';
+import customGroupOrderRule from '../rule-definition.js';
+
+run({
+  name: 'vanilla-extract/custom-order/defaults',
+  rule: customGroupOrderRule,
+  languageOptions: {
+    parser: tsParser,
+    parserOptions: {
+      ecmaVersion: 2022,
+      sourceType: 'module',
+    },
+  },
+  valid: [
+    // Test with no options provided - should use defaults
+    `
+      import { style } from '@vanilla-extract/css';
+      const myStyle = style({
+        alignItems: 'center',
+        backgroundColor: 'red',
+        color: 'blue',
+        display: 'flex',
+        margin: '10px',
+        padding: '20px',
+        zIndex: 1
+      });
+    `,
+
+    // Test with empty groupOrder array - should use defaults
+    {
+      code: `
+        import { style } from '@vanilla-extract/css';
+        const myStyle = style({
+          alignItems: 'center',
+          backgroundColor: 'red',
+          color: 'blue',
+          display: 'flex',
+          margin: '10px',
+          padding: '20px',
+          zIndex: 1
+        });
+      `,
+      options: [
+        {
+          groupOrder: [],
+        },
+      ],
+    },
+  ],
+  invalid: [
+    // Test with no options provided - should use alphabetical ordering by default
+    {
+      code: `
+        import { style } from '@vanilla-extract/css';
+        const myStyle = style({
+          zIndex: 1,
+          padding: '20px',
+          margin: '10px',
+          display: 'flex',
+          color: 'blue',
+          backgroundColor: 'red',
+          alignItems: 'center'
+        });
+      `,
+      errors: [{ messageId: 'alphabeticalOrder' }],
+      output: `
+        import { style } from '@vanilla-extract/css';
+        const myStyle = style({
+          alignItems: 'center',
+          backgroundColor: 'red',
+          color: 'blue',
+          display: 'flex',
+          margin: '10px',
+          padding: '20px',
+          zIndex: 1
+        });
+      `,
+    },
+
+    // Test with empty groupOrder array - should use alphabetical ordering by default
+    {
+      code: `
+        import { style } from '@vanilla-extract/css';
+        const myStyle = style({
+          zIndex: 1,
+          padding: '20px',
+          margin: '10px',
+          display: 'flex',
+          color: 'blue',
+          backgroundColor: 'red',
+          alignItems: 'center'
+        });
+      `,
+      options: [
+        {
+          groupOrder: [],
+        },
+      ],
+      errors: [{ messageId: 'alphabeticalOrder' }],
+      output: `
+        import { style } from '@vanilla-extract/css';
+        const myStyle = style({
+          alignItems: 'center',
+          backgroundColor: 'red',
+          color: 'blue',
+          display: 'flex',
+          margin: '10px',
+          padding: '20px',
+          zIndex: 1
+        });
+      `,
+    },
+  ],
+});