extract substring tool, testCases then updated index file

src/pages/string/extract-substring/extract-substring.service.test.ts

@@ -0,0 +1,57 @@
+import { expect, describe, it } from 'vitest';
+import { extractSubstring } from './service';
+
+describe('extractSubstring', () => {
+    it('should extract a substring from single-line input', () => {
+        const input = 'hello world';
+        const result = extractSubstring(input, 1, 4, false, false);
+        expect(result).toBe('hell');
+    });
+
+    it('should extract and reverse a substring from single-line input', () => {
+        const input = 'hello world';
+        const result = extractSubstring(input, 1, 5, false, true);
+        expect(result).toBe('olleh');
+    });
+
+    it('should extract substrings from multi-line input', () => {
+        const input = 'hello\nworld';
+        const result = extractSubstring(input, 1, 5, true, false);
+        expect(result).toBe('hello\nworld');
+    });
+
+    it('should extract and reverse substrings from multi-line input', () => {
+        const input = 'hello\nworld';
+        const result = extractSubstring(input, 1, 4, true, true);
+        expect(result).toBe('lleh\nlrow');
+    });
+
+    it('should handle empty input', () => {
+        const input = '';
+        const result = extractSubstring(input, 1, 5, false, false);
+        expect(result).toBe('');
+    });
+
+    it('should handle start and length out of bounds', () => {
+        const input = 'hello';
+        const result = extractSubstring(input, 10, 5, false, false);
+        expect(result).toBe('');
+    });
+
+    it('should handle negative start and length', () => {
+        expect(() => extractSubstring('hello', -1, 5, false, false)).toThrow("Start index must be greater than zero.");
+        expect(() => extractSubstring('hello', 1, -5, false, false)).toThrow("Length value must be greater than or equal to zero.");
+    });
+
+    it('should handle zero length', () => {
+        const input = 'hello';
+        const result = extractSubstring(input, 1, 0, false, false);
+        expect(result).toBe('');
+    });
+
+    it('should work', () => {
+        const input = 'je me nomme king\n22 est mon chiffre';
+        const result = extractSubstring(input, 12, 7, true, false);
+        expect(result).toBe(' king\nchiffre');
+    });
+});