test: improve test descriptions and remove redundant edge cases

- Clarify test descriptions to be more descriptive and positive
- Remove duplicate tests for undefined/null processor return values
- Clean up test suite while maintaining comprehensive coverage

Author: hex-ci

CLAUDE.md

@@ -0,0 +1,58 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Development Commands
+
+### Testing
+- `npm test` - Run all tests using Jest
+- `npm run test:coverage` - Run tests with coverage report
+- `npx jest --testNamePattern="test name"` - Run a specific test by name pattern
+
+### Project Structure
+
+This is a PostCSS plugin that processes CSS units through a configurable processor function. It's a single-purpose plugin with a focused architecture.
+
+## Core Architecture
+
+The plugin consists of a main entry point (`index.js`) with several key architectural components:
+
+### Main Plugin Function (`module.exports`)
+- Returns a PostCSS plugin object with `postcssPlugin`, `Once`, `Declaration`, and `AtRule` hooks
+- Handles plugin configuration merging with defaults
+- Manages file exclusion logic and unit regex compilation
+
+### Key Processing Components
+
+1. **Unit Detection & Regex (`createUnitRegex`)**
+   - Combines default CSS units with custom units from options
+   - Creates a regex that excludes quoted strings and URLs but matches unit values
+   - Pattern: `"[^"]+"|'[^']+'|url\([^)]+\)|var\([^)]+\)|(\d*\.?\d+)(${unitStr})`
+
+2. **Property List Matching (`createPropListMatcher`)**
+   - Supports wildcards (`*`), exact matches, and negation patterns (`!`)
+   - Handles `startWith`, `endWith`, `contain`, and their negative variants
+   - Returns a function that tests if a CSS property should be processed
+
+3. **Unit Processing (`createUnitReplace`)**
+   - Calls the user-provided processor function with value, unit, node, and root
+   - Handles different processor return types: number, string, or object with value/unit
+   - Applies precision rounding via `toFixed` helper
+
+4. **Selector Blacklisting (`blacklistedSelector`)**
+   - Supports string includes and regex pattern matching
+   - Used to skip processing for specific CSS selectors
+
+### Plugin Hooks
+
+- **`Once`**: Sets up file exclusion logic and initializes the unit replacement function
+- **`Declaration`**: Processes CSS property values, handles replacement vs. cloning
+- **`AtRule`**: Processes media query parameters when `mediaQuery` option is enabled
+
+### Configuration Options
+
+The plugin accepts extensive configuration through the options object, with sensible defaults for all settings. Key options include processor function, unit precision, property filtering, selector blacklisting, and file exclusion patterns.
+
+### Type Safety
+
+TypeScript definitions are provided in `index.d.ts` with comprehensive interface documentation for all configuration options and the processor function signature.

index.test.js

@@ -135,7 +135,7 @@ describe('postcss-unit-processor', () => {
   });
 
   // Test exclude option with function
-  it('should not exclude files when file path is undefined', async () => {
+  it('should process CSS when file path is undefined', async () => {
     const processor = (value, unit) => {
       if (unit === 'px') {
         return { value: value * 2, unit: 'px' };
@@ -148,7 +148,7 @@ describe('postcss-unit-processor', () => {
   });
 
   // Test exclude option with string
-  it('should not exclude files when file path does not match string', async () => {
+  it('should process CSS when file path does not match exclude string', async () => {
     const processor = (value, unit) => {
       if (unit === 'px') {
         return { value: value * 2, unit: 'px' };
@@ -161,7 +161,7 @@ describe('postcss-unit-processor', () => {
   });
 
   // Test exclude option with regex
-  it('should not exclude files when file path does not match regex', async () => {
+  it('should process CSS when file path does not match exclude regex', async () => {
     const processor = (value, unit) => {
       if (unit === 'px') {
         return { value: value * 2, unit: 'px' };
@@ -420,7 +420,7 @@ describe('postcss-unit-processor', () => {
   });
 
   // Test blacklistedSelector function directly by manipulating parent selector
-  it('should handle declaration with non-string parent selector', async () => {
+  it('should handle selector blacklist check with edge cases', async () => {
     const processor = (value, unit) => {
       if (unit === 'px') {
         return { value: value * 2, unit: 'px' };
@@ -521,21 +521,6 @@ describe('postcss-unit-processor', () => {
     );
   });
 
-  // Test processor returning object with undefined value
-  it('should handle processor returning object with undefined value', async () => {
-    const processor = (value, unit) => {
-      if (unit === 'px') {
-        return { value: undefined, unit: 'px' };
-      }
-      return { value, unit };
-    };
-    await testProcess(
-      'div { width: 100px; }',
-      'div { width: 0; }',
-      { processor }
-    );
-  });
-
   // Test processor returning object with falsy unit
   it('should handle processor returning object with falsy unit', async () => {
     const processor = (value, unit) => {
@@ -551,21 +536,6 @@ describe('postcss-unit-processor', () => {
     );
   });
 
-  // Test processor returning object with null unit
-  it('should handle processor returning object with null unit', async () => {
-    const processor = (value, unit) => {
-      if (unit === 'px') {
-        return { value: 50, unit: null };
-      }
-      return { value, unit };
-    };
-    await testProcess(
-      'div { width: 100px; }',
-      'div { width: 50px; }',
-      { processor }
-    );
-  });
-
   // Test processor returning string number
   it('should handle processor returning string number', async () => {
     const processor = (value, unit) => {
@@ -650,12 +620,4 @@ describe('postcss-unit-processor', () => {
     expect(result.warnings()).toHaveLength(0);
   });
 
-  // Test unitProcessor with undefined options (default parameter)
-  it('should handle unitProcessor called with undefined options', async () => {
-    const input = 'div { width: 100px; }';
-    const result = await postcss([unitProcessor(undefined)])
-      .process(input, { from: undefined });
-    expect(result.css).toEqual('div { width: 100px; }');
-    expect(result.warnings()).toHaveLength(0);
-  });
 });