diff --git a/test/stylish-formatter.test.js b/test/stylish-formatter.test.js
index c942946..5f6f92e 100644
--- a/test/stylish-formatter.test.js
+++ b/test/stylish-formatter.test.js
@@ -4,11 +4,15 @@
  * License under MIT
  * ========================================================================== */
 
+import { sep } from 'node:path';
 import stylishFormatter from '../src/stylish-formatter.mjs';
 
 import { cleanFormatterOutput } from './testUtils/cleanOutput.js';
 
-describe('stylishFormatter', () => {
+import colors from 'ansi-colors';
+const { blue, dim, green, red, yellow } = colors;
+
+describe('Stylish built-in formatter', () => {
   let actualTTY;
   let actualColumns;
 
@@ -22,12 +26,10 @@ describe('stylishFormatter', () => {
     process.stdout.columns = actualColumns;
   });
 
-  it('should outputs no errors or warnings', () => {
+  it('should handle results with no warnings or errors gracefully', () => {
     const results = [
-      {
-        source: 'path/to/file.css',
-        warnings: [],
-      },
+      { source: 'path/to/file1.css', warnings: [] },
+      { source: 'path/to/file2.css', warnings: [] }
     ];
 
     const returnValue = { ruleMetadata: {} };
@@ -36,7 +38,7 @@ describe('stylishFormatter', () => {
 
     expect(output).toBe('');
   });
-  it('should outputs no valid files', () => {
+  it('should handle empty results array without throwing errors', () => {
     const results = [];
 
     const returnValue = { ruleMetadata: {} };
@@ -50,19 +52,13 @@ describe('stylishFormatter', () => {
       {
         source: 'path/to/file.css',
         warnings: [
-          {
-            line: 1,
-            column: 1,
-            rule: 'bar',
-            severity: 'error',
-            text: 'Unexpected foo',
-          },
-        ],
-      },
+          { severity: 'error', line: 1, column: 1, text: 'Unexpected foo', rule: 'bar' }
+        ]
+      }
     ];
 
     const expectedOutput = [
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:1  ×  Unexpected foo    bar',
       '',
       '× 1 problem (1 error, 0 warnings)'
@@ -73,45 +69,27 @@ describe('stylishFormatter', () => {
     expect(output).toBe(expectedOutput);
   });
   it('should outputs fixable error and warning counts', () => {
-		const results = [
-			{
-				source: 'path/to/file.css',
-				warnings: [
-					{
-						line: 1,
-						column: 1,
-						rule: 'no-foo',
-						severity: 'error',
-						text: 'Unexpected foo',
-					},
-					{
-						line: 2,
-						column: 1,
-						rule: 'no-bar',
-						severity: 'error',
-						text: 'Unexpected bar',
-					},
-					{
-						line: 3,
-						column: 1,
-						rule: 'no-baz',
-						severity: 'warning',
-						text: 'Unexpected baz',
-					},
-				],
-			},
-		];
-
-		const returnValue = {
-			ruleMetadata: {
-				'no-foo': { fixable: true },
-				'no-bar': { fixable: false },
-				'no-baz': { fixable: true },
-			},
-		};
+    const results = [
+      {
+        source: 'path/to/file.css',
+        warnings: [
+          { severity: 'error', line: 1, column: 1, text: 'Unexpected foo', rule: 'no-foo' },
+          { severity: 'error', line: 2, column: 1, text: 'Unexpected bar', rule: 'no-bar' },
+          { severity: 'warning', line: 3, column: 1, text: 'Unexpected baz', rule: 'no-baz' }
+        ]
+      }
+    ];
+
+    const returnValue = {
+      ruleMetadata: {
+        'no-foo': { fixable: true },
+        'no-bar': { fixable: false },
+        'no-baz': { fixable: true }
+      }
+    };
 
     const expectedOutput = [
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:1  ×  Unexpected foo  o  no-foo',
       '  2:1  ×  Unexpected bar     no-bar',
       '  3:1  ‼  Unexpected baz  o  no-baz',
@@ -120,41 +98,29 @@ describe('stylishFormatter', () => {
       '  1 error and 1 warning potentially fixable with the "fix: true" option.'
     ].join('\n');
 
-		const output = cleanFormatterOutput(stylishFormatter, results, returnValue);
+    const output = cleanFormatterOutput(stylishFormatter, results, returnValue);
 
-		expect(output).toBe(expectedOutput);
-	});
+    expect(output).toBe(expectedOutput);
+  });
   it('should outputs fixable error counts', () => {
-		const results = [
-			{
-				source: 'path/to/file.css',
-				warnings: [
-					{
-						line: 1,
-						column: 1,
-						rule: 'no-foo',
-						severity: 'error',
-						text: 'Unexpected foo',
-					},
-					{
-						line: 2,
-						column: 1,
-						rule: 'no-bar',
-						severity: 'error',
-						text: 'Unexpected bar',
-					},
-				],
-			},
-		];
-
-		const returnValue = {
-			ruleMetadata: {
-				'no-foo': { fixable: true },
-			},
-		};
+    const results = [
+      {
+        source: 'path/to/file.css',
+        warnings: [
+          { severity: 'error', line: 1, column: 1, text: 'Unexpected foo', rule: 'no-foo' },
+          { severity: 'error', line: 2, column: 1, text: 'Unexpected bar', rule: 'no-bar' }
+        ]
+      }
+    ];
+
+    const returnValue = {
+      ruleMetadata: {
+        'no-foo': { fixable: true }
+      }
+    };
 
     const expectedOutput = [
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:1  ×  Unexpected foo  o  no-foo',
       '  2:1  ×  Unexpected bar     no-bar',
       '',
@@ -162,41 +128,29 @@ describe('stylishFormatter', () => {
       '  1 error potentially fixable with the "fix: true" option.'
     ].join('\n');
 
-		const output = cleanFormatterOutput(stylishFormatter, results, returnValue);
+    const output = cleanFormatterOutput(stylishFormatter, results, returnValue);
 
-		expect(output).toBe(expectedOutput);
-	});
+    expect(output).toBe(expectedOutput);
+  });
   it('should outputs fixable warning counts', () => {
     const results = [
       {
         source: 'path/to/file.css',
         warnings: [
-          {
-            line: 1,
-            column: 1,
-            rule: 'no-foo',
-            severity: 'error',
-            text: 'Unexpected foo',
-          },
-          {
-            line: 2,
-            column: 1,
-            rule: 'no-bar',
-            severity: 'warning',
-            text: 'Unexpected bar',
-          },
-        ],
-      },
+          { severity: 'error', line: 1, column: 1, text: 'Unexpected foo', rule: 'no-foo' },
+          { severity: 'warning', line: 2, column: 1, text: 'Unexpected bar', rule: 'no-bar' }
+        ]
+      }
     ];
 
     const returnValue = {
       ruleMetadata: {
-        'no-bar': { fixable: true },
-      },
+        'no-bar': { fixable: true }
+      }
     };
 
     const expectedOutput = [
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:1  ×  Unexpected foo     no-foo',
       '  2:1  ‼  Unexpected bar  o  no-bar',
       '',
@@ -213,41 +167,23 @@ describe('stylishFormatter', () => {
       {
         source: 'path/to/file.css',
         warnings: [
-          {
-            line: 1,
-            column: 2,
-            rule: 'no-foo',
-            severity: 'error',
-            text: 'Unexpected foo',
-          },
-          {
-            line: 1,
-            column: 2,
-            rule: 'no-bar',
-            severity: 'warning',
-            text: 'Unexpected bar',
-          },
-          {
-            line: 1,
-            column: 2,
-            rule: 'no-baz',
-            severity: 'warning',
-            text: 'Unexpected baz',
-          },
-        ],
-      },
+          { severity: 'error', line: 1, column: 2, text: 'Unexpected foo', rule: 'no-foo' },
+          { severity: 'warning', line: 1, column: 2, text: 'Unexpected bar', rule: 'no-bar' },
+          { severity: 'warning', line: 1, column: 2, text: 'Unexpected baz', rule: 'no-baz' }
+        ]
+      }
     ];
 
     const returnValue = {
       ruleMetadata: {
         'no-foo': {}, // fixable should exist
         'no-bar': { fixable: 900 }, // fixable should be a boolean
-        'no-baz': { fixable: true },
-      },
+        'no-baz': { fixable: true }
+      }
     };
 
     const expectedOutput = [
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:2  ×  Unexpected foo     no-foo',
       '  1:2  ‼  Unexpected bar     no-bar',
       '  1:2  ‼  Unexpected baz  o  no-baz',
@@ -260,33 +196,51 @@ describe('stylishFormatter', () => {
 
     expect(output).toBe(expectedOutput);
   });
+  it('should correctly apply color formatting to error and warning messages', () => {
+    const results = [
+      {
+        source: 'test.css',
+        warnings: [
+          { severity: 'error', line: 1, column: 1, text: 'Error message', rule: 'error-rule' },
+          { severity: 'warning', line: 2, column: 2, text: 'Warning message', rule: 'warning-rule' }
+        ]
+      }
+    ];
+
+    const returnValue = {
+      ruleMetadata: {
+        'error-rule': { fixable: true },
+        'warning-rule': { fixable: true }
+      }
+    };
+
+    const output = stylishFormatter(results, returnValue);
+
+    expect(output).toContain(blue('test.css'));
+    expect(output).toContain(red('✖'));
+    expect(output).toContain(yellow('⚠'));
+    expect(output).toContain(green('♻'));
+    expect(output).toContain(dim('error-rule'));
+    expect(output).toContain(dim('warning-rule'));
+    expect(output).toContain(red('1 error'));
+    expect(output).toContain(yellow('1 warning'));
+    expect(output).toContain(green('"fix: true"'));
+  });
   it('should outputs results with missing ruleMetadata object', () => {
-		const results = [
-			{
-				source: 'path/to/file.css',
-				warnings: [
-					{
-						line: 1,
-						column: 2,
-						rule: 'no-foo',
-						severity: 'error',
-						text: 'Unexpected foo',
-					},
-					{
-						line: 1,
-						column: 2,
-						rule: 'no-bar',
-						severity: 'warning',
-						text: 'Unexpected bar',
-					},
-				],
-			},
-		];
-
-		const returnValue = { ruleMetadata: null };
+    const results = [
+      {
+        source: 'path/to/file.css',
+        warnings: [
+          { severity: 'error', line: 1, column: 2, text: 'Unexpected foo', rule: 'no-foo' },
+          { severity: 'warning', line: 1, column: 2, text: 'Unexpected bar', rule: 'no-bar' }
+        ]
+      }
+    ];
+
+    const returnValue = { ruleMetadata: null };
 
     const expectedOutput = [
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:2  ×  Unexpected foo    no-foo',
       '  1:2  ‼  Unexpected bar    no-bar',
       '',
@@ -302,19 +256,13 @@ describe('stylishFormatter', () => {
       {
         source: 'path/to/file.css',
         warnings: [
-          {
-            line: 1,
-            column: 1,
-            rule: 'bar',
-            severity: 'warning',
-            text: 'Unexpected foo',
-          },
-        ],
+          { severity: 'warning', line: 1, column: 1, text: 'Unexpected foo', rule: 'bar' }
+        ]
       }
     ];
 
     const expectedOutput = [
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:1  ‼  Unexpected foo    bar',
       '',
       '‼ 1 problem (0 errors, 1 warning)'
@@ -329,34 +277,22 @@ describe('stylishFormatter', () => {
       {
         source: 'path/to/file-a.css',
         warnings: [
-          {
-            line: 1,
-            column: 2,
-            rule: 'no-foo',
-            severity: 'error',
-            text: 'Unexpected foo',
-          },
-        ],
+          { severity: 'error', line: 1, column: 2, text: 'Unexpected foo', rule: 'no-foo' }
+        ]
       },
       {
         source: 'path/to/file-b.css',
         warnings: [
-          {
-            line: 1,
-            column: 2,
-            rule: 'no-bar',
-            severity: 'warning',
-            text: 'Unexpected bar',
-          },
-        ],
-      },
+          { severity: 'warning', line: 1, column: 2, text: 'Unexpected bar', rule: 'no-bar' }
+        ]
+      }
     ];
 
     const expectedOutput = [
-      'path/to/file-a.css',
+      `path${sep}to${sep}file-a.css`,
       '  1:2  ×  Unexpected foo    no-foo',
       '',
-      'path/to/file-b.css',
+      `path${sep}to${sep}file-b.css`,
       '  1:2  ‼  Unexpected bar    no-bar',
       '',
       '× 2 problems (1 error, 1 warning)'
@@ -366,24 +302,18 @@ describe('stylishFormatter', () => {
 
     expect(output).toBe(expectedOutput);
   });
-	it('should removes rule name from warning text', () => {
-		const results = [
-			{
-				source: 'path/to/file.css',
-				warnings: [
-					{
-						line: 1,
-						column: 1,
-						rule: 'rule-name',
-						severity: 'warning',
-						text: 'Unexpected foo (rule-name)',
-					},
-				],
-			},
-		];
+  it('should removes rule name from warning text', () => {
+    const results = [
+      {
+        source: 'path/to/file.css',
+        warnings: [
+          { severity: 'warning', line: 1, column: 1, text: 'Unexpected foo (rule-name)', rule: 'rule-name' }
+        ]
+      }
+    ];
 
     const expectedOutput = [
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:1  ‼  Unexpected foo    rule-name',
       '',
       '‼ 1 problem (0 errors, 1 warning)'
@@ -392,27 +322,21 @@ describe('stylishFormatter', () => {
     const output = cleanFormatterOutput(stylishFormatter, results);
 
     expect(output).toBe(expectedOutput);
-	});
-	it('should outputs warnings without stdout `TTY`', () => {
-		process.stdout.isTTY = false;
-
-		const results = [
-			{
-				source: 'path/to/file.css',
-				warnings: [
-					{
-						line: 1,
-						column: 1,
-						rule: 'bar',
-						severity: 'error',
-						text: 'Unexpected foo',
-					},
-				],
-			},
-		];
+  });
+  it('should outputs warnings without stdout `TTY`', () => {
+    process.stdout.isTTY = false;
+
+    const results = [
+      {
+        source: 'path/to/file.css',
+        warnings: [
+          { severity: 'error', line: 1, column: 1, text: 'Unexpected foo', rule: 'bar' }
+        ]
+      }
+    ];
 
     const expectedOutput = [
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:1  ×  Unexpected foo    bar',
       '',
       '× 1 problem (1 error, 0 warnings)'
@@ -421,7 +345,7 @@ describe('stylishFormatter', () => {
     const output = cleanFormatterOutput(stylishFormatter, results);
 
     expect(output).toBe(expectedOutput);
-	});
+  });
   it('should condenses deprecations and invalid option warnings', () => {
     const results = [
       {
@@ -429,31 +353,31 @@ describe('stylishFormatter', () => {
         deprecations: [
           {
             text: 'Deprecated foo.',
-            reference: 'bar',
-          },
+            reference: 'bar'
+          }
         ],
         invalidOptionWarnings: [
           {
-            text: 'Unexpected option for baz',
-          },
+            text: 'Unexpected option for baz'
+          }
         ],
-        warnings: [],
+        warnings: []
       },
       {
         source: 'path/to/file2.css',
         deprecations: [
           {
             text: 'Deprecated foo.',
-            reference: 'bar',
-          },
+            reference: 'bar'
+          }
         ],
         invalidOptionWarnings: [
           {
-            text: 'Unexpected option for baz',
-          },
+            text: 'Unexpected option for baz'
+          }
         ],
-        warnings: [],
-      },
+        warnings: []
+      }
     ];
 
     const expectedOutput = [
@@ -474,47 +398,35 @@ describe('stylishFormatter', () => {
         deprecations: [
           {
             text: 'Deprecated foo.',
-            reference: 'bar',
-          },
+            reference: 'bar'
+          }
         ],
         invalidOptionWarnings: [
           {
-            text: 'Unexpected option for baz',
-          },
+            text: 'Unexpected option for baz'
+          }
         ],
         warnings: [
-          {
-            line: 1,
-            column: 1,
-            rule: 'bar',
-            severity: 'warning',
-            text: 'Unexpected foo',
-          },
-        ],
+          { severity: 'warning', line: 1, column: 1, text: 'Unexpected foo', rule: 'bar' }
+        ]
       },
       {
         source: 'path/to/file2.css',
         deprecations: [
           {
             text: 'Deprecated foo.',
-            reference: 'bar',
-          },
+            reference: 'bar'
+          }
         ],
         invalidOptionWarnings: [
           {
-            text: 'Unexpected option for baz',
-          },
+            text: 'Unexpected option for baz'
+          }
         ],
         warnings: [
-          {
-            line: 1,
-            column: 1,
-            rule: 'bar',
-            severity: 'warning',
-            text: 'Unexpected foo',
-          },
-        ],
-      },
+          { severity: 'warning', line: 1, column: 1, text: 'Unexpected foo', rule: 'bar' }
+        ]
+      }
     ];
 
     const expectedOutput = [
@@ -523,10 +435,10 @@ describe('stylishFormatter', () => {
       'Deprecation warnings:',
       ' - Deprecated foo. See: bar',
       '',
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:1  ‼  Unexpected foo    bar',
       '',
-      'path/to/file2.css',
+      `path${sep}to${sep}file2.css`,
       '  1:1  ‼  Unexpected foo    bar',
       '',
       '‼ 2 problems (0 errors, 2 warnings)'
@@ -541,32 +453,26 @@ describe('stylishFormatter', () => {
       {
         source: 'path/to/file.css',
         warnings: [],
-        ignored: true,
-      },
+        ignored: true
+      }
     ];
 
     const output = cleanFormatterOutput(stylishFormatter, results);
 
     expect(output).toBe('');
   });
-	it('should handles empty messages', () => {
-		const results = [
-			{
-				source: 'path/to/file.css',
-				warnings: [
-					{
-						line: 1,
-						column: 1,
-						rule: 'bar',
-						severity: 'error',
-						text: '',
-					},
-				],
-			},
-		];
+  it('should handles empty messages', () => {
+    const results = [
+      {
+        source: 'path/to/file.css',
+        warnings: [
+          { severity: 'error', line: 1, column: 1, text: '', rule: 'bar' }
+        ]
+      }
+    ];
 
     const expectedOutput = [
-      'path/to/file.css',
+      `path${sep}to${sep}file.css`,
       '  1:1  ×      bar',
       '',
       '× 1 problem (1 error, 0 warnings)'
@@ -576,4 +482,46 @@ describe('stylishFormatter', () => {
 
     expect(output).toBe(expectedOutput);
   });
+  it('should correctly pluralize "problem" based on the total count', () => {
+    const results = [
+      {
+        source: 'file1.css',
+        warnings: [
+          { severity: 'error', line: 1, column: 1, text: 'Error 1', rule: 'error-rule-1' }
+        ]
+      },
+      {
+        source: 'file2.css',
+        warnings: [
+          { severity: 'warning', line: 1, column: 1, text: 'Warning 1', rule: 'warning-rule-1' },
+          { severity: 'error', line: 2, column: 2, text: 'Error 2', rule: 'error-rule-2' }
+        ]
+      }
+    ];
+
+    const returnValue = {
+      ruleMetadata: {
+        'error-rule-1': { },
+        'warning-rule-1': { },
+        'error-rule-2': { }
+      }
+    };
+
+    const output = cleanFormatterOutput(stylishFormatter, results, returnValue);
+
+    expect(output).toContain('3 problems (2 errors, 1 warning)');
+
+    const singleResult = [
+      {
+        source: 'file1.css',
+        warnings: [
+          { severity: 'error', line: 1, column: 1, text: 'Error 1', rule: 'error-rule-1' }
+        ]
+      }
+    ];
+
+    const singleOutput = cleanFormatterOutput(stylishFormatter, singleResult, returnValue);
+
+    expect(singleOutput).toContain('1 problem (1 error, 0 warnings)');
+  });
 });
diff --git a/test/testUtils/cleanOutput.js b/test/testUtils/cleanOutput.js
index 0b2f2c3..17d8a37 100644
--- a/test/testUtils/cleanOutput.js
+++ b/test/testUtils/cleanOutput.js
@@ -16,8 +16,10 @@ symbolConversions.set('✖', '×');
 symbolConversions.set('♻', 'o');
 
 /**
- * @param {string} output
- * @returns {string}
+ * Cleans and transforms the output string by removing ANSI styling and replacing certain symbols.
+ *
+ * @param {string} output - The original output string to be cleaned.
+ * @returns {string} The cleaned and transformed output string.
  */
 function getCleanOutput(output) {
   let cleanOutput = unstyle(output).trim();
@@ -30,10 +32,12 @@ function getCleanOutput(output) {
 }
 
 /**
- * @param {import('stylelint').Formatter} formatter
- * @param {import('stylelint').LintResult[]} results
- * @param {Pick<import('stylelint').LinterResult, 'ruleMetadata'>} [returnValue]
- * @returns {string}
+ * Cleans and formats the output of a Stylelint formatter.
+ *
+ * @param {import('stylelint').Formatter} formatter - The Stylelint formatter function to be used.
+ * @param {import('stylelint').LintResult[]} results - An array of Stylelint lint results to be formatted.
+ * @param {Pick<import('stylelint').LinterResult, 'ruleMetadata'>} [returnValue={ ruleMetadata: {} }] - Optional return value with rule metadata.
+ * @returns {string} The cleaned and formatted output string.
  */
 export function cleanFormatterOutput(formatter, results, returnValue = { ruleMetadata: {} }) {
   return getCleanOutput(formatter(results, returnValue));