test: add regression tests for normalization of smooth curves

src/tests/normalize_curves.test.ts

@@ -1,40 +1,85 @@
 import { describe, test, expect } from '@jest/globals';
 import { SVGPathData } from '../index.js';
 
+function testNormalizeST(path: string) {
+  const pathData = new SVGPathData(path).normalizeST();
+  return pathData.encode();
+}
+
 describe('normalization of curves', () => {
   test("should ignore everything which isn't S s T t", () => {
     expect(
-      new SVGPathData(
-        'm20,30c0 0 10 20 15 30q10 20 15 30h10v10a10 10 5 1 0 10 10z',
-      )
-        .normalizeST()
-        .encode(),
-    ).toEqual(
-      new SVGPathData(
+      testNormalizeST(
         'm20,30c0 0 10 20 15 30q10 20 15 30h10v10a10 10 5 1 0 10 10z',
-      ).encode(),
-    );
+      ),
+    ).toEqual('m20 30c0 0 10 20 15 30q10 20 15 30h10v10a10 10 5 1 0 10 10z');
   });
 
   test("should take the previous point as the curve parameter if the previous curve isn't of the same type", () => {
-    expect(
-      new SVGPathData('M 10 10 h 100 s 10 20 15 30 t 20 15')
-        .normalizeST()
-        .encode(),
-    ).toEqual(
-      new SVGPathData('M 10 10 h 100 c 0 0 10 20 15 30 q 0 0 20 15').encode(),
+    expect(testNormalizeST('M 10 10 h 100 s 10 20 15 30 t 20 15')).toEqual(
+      'M10 10h100c0 0 10 20 15 30q0 0 20 15',
     );
   });
 
   test('should mirror the previous control point', () => {
+    expect(testNormalizeST('M 10 10 s 10 20 15 30 S 90 80 100 100')).toEqual(
+      'M10 10c0 0 10 20 15 30C30 50 90 80 100 100',
+    );
+  });
+
+  test('should handle multiple consecutive smooth cubic curves', () => {
+    expect(
+      testNormalizeST(
+        'M 10 10 C 20 20 30 30 40 40 S 60 60 70 70 S 90 90 100 100',
+      ),
+    ).toEqual('M10 10C20 20 30 30 40 40C50 50 60 60 70 70C80 80 90 90 100 100');
+  });
+
+  test('should handle multiple consecutive smooth quadratic curves', () => {
+    expect(testNormalizeST('M 10 10 Q 20 30 30 40 T 50 60 T 70 80')).toEqual(
+      'M10 10Q20 30 30 40Q40 50 50 60Q60 70 70 80',
+    );
+  });
+
+  test('should handle mixed absolute and relative smooth curves', () => {
     expect(
-      new SVGPathData('M 10 10 s 10 20 15 30 S 90 80 100 100')
-        .normalizeST()
-        .encode(),
+      testNormalizeST('M 10 10 C 20 30 30 40 40 50 s 30 40 40 50'),
+    ).toEqual('M10 10C20 30 30 40 40 50c10 10 30 40 40 50');
+
+    expect(testNormalizeST('M 10 10 Q 20 30 30 40 t 40 50')).toEqual(
+      'M10 10Q20 30 30 40q10 10 40 50',
+    );
+  });
+
+  test('should correctly reflect control points at inflection points', () => {
+    expect(
+      testNormalizeST('M 10 10 C 40 10 60 40 60 60 S 10 90 10 60'),
+    ).toEqual('M10 10C40 10 60 40 60 60C60 80 10 90 10 60');
+  });
+
+  test('should handle relative coordinates with large values', () => {
+    expect(
+      testNormalizeST('m 10 10 c 50 0 100 50 100 100 s -50 100 -100 100'),
+    ).toEqual('m10 10c50 0 100 50 100 100c0 50 -50 100 -100 100');
+  });
+
+  test('should correctly handle reflection in complex paths', () => {
+    expect(
+      testNormalizeST(
+        'M 20 20 C 40 40 60 40 80 20 S 120 0 140 20 C 160 40 160 60 140 80 s -40 0 -60 -20',
+      ),
     ).toEqual(
-      new SVGPathData(
-        'M 10 10 c 0 0 10 20 15 30 C 30 50 90 80 100 100',
-      ).encode(),
+      'M20 20C40 40 60 40 80 20C100 0 120 0 140 20C160 40 160 60 140 80c-20 20 -40 0 -60 -20',
+    );
+  });
+
+  test('should handle smooth curves after non-curve commands', () => {
+    expect(testNormalizeST('M 10 10 L 50 50 S 70 80 90 90')).toEqual(
+      'M10 10L50 50C50 50 70 80 90 90',
+    );
+
+    expect(testNormalizeST('M 10 10 H 50 T 90 50')).toEqual(
+      'M10 10H50Q50 10 90 50',
     );
   });
 });