test: add tests for codePointAt

src/__tests__/codePaintAt.test.js

@@ -0,0 +1,75 @@
+import codePointAt from '../codePointAt';
+
+const testCases = [
+  // String that starts with a BMP symbol
+  { value: 'abc\uD834\uDF06def', at: '', toBe: 0x61 },
+  { value: 'abc\uD834\uDF06def', at: '_', toBe: 0x61 },
+  { value: 'abc\uD834\uDF06def', at: -Infinity, toBe: undefined },
+  { value: 'abc\uD834\uDF06def', at: -1, toBe: undefined },
+  { value: 'abc\uD834\uDF06def', at: -0, toBe: 0x61 },
+  { value: 'abc\uD834\uDF06def', at: 0, toBe: 0x61 },
+  { value: 'abc\uD834\uDF06def', at: 3, toBe: 0x1d306 },
+  { value: 'abc\uD834\uDF06def', at: 4, toBe: 0xdf06 },
+  { value: 'abc\uD834\uDF06def', at: 5, toBe: 0x64 },
+  { value: 'abc\uD834\uDF06def', at: 42, toBe: undefined },
+  { value: 'abc\uD834\uDF06def', at: Infinity, toBe: undefined },
+  { value: 'abc\uD834\uDF06def', at: Infinity, toBe: undefined },
+  { value: 'abc\uD834\uDF06def', at: NaN, toBe: 0x61 },
+  { value: 'abc\uD834\uDF06def', at: false, toBe: 0x61 },
+  { value: 'abc\uD834\uDF06def', at: null, toBe: 0x61 },
+  { value: 'abc\uD834\uDF06def', at: undefined, toBe: 0x61 },
+
+  // String that starts with an astral symbol
+  { value: '\uD834\uDF06def', at: '', toBe: 0x1d306 },
+  { value: '\uD834\uDF06def', at: '1', toBe: 0xdf06 },
+  { value: '\uD834\uDF06def', at: '_', toBe: 0x1d306 },
+  { value: '\uD834\uDF06def', at: -1, toBe: undefined },
+  { value: '\uD834\uDF06def', at: -0, toBe: 0x1d306 },
+  { value: '\uD834\uDF06def', at: 0, toBe: 0x1d306 },
+  { value: '\uD834\uDF06def', at: 1, toBe: 0xdf06 },
+  { value: '\uD834\uDF06def', at: 42, toBe: undefined },
+  { value: '\uD834\uDF06def', at: false, toBe: 0x1d306 },
+  { value: '\uD834\uDF06def', at: null, toBe: 0x1d306 },
+  { value: '\uD834\uDF06def', at: undefined, toBe: 0x1d306 },
+
+  // Lone high surrogates
+  { value: '\uD834abc', at: '', toBe: 0xd834 },
+  { value: '\uD834abc', at: '_', toBe: 0xd834 },
+  { value: '\uD834abc', at: -1, toBe: undefined },
+  { value: '\uD834abc', at: -0, toBe: 0xd834 },
+  { value: '\uD834abc', at: 0, toBe: 0xd834 },
+  { value: '\uD834abc', at: false, toBe: 0xd834 },
+  { value: '\uD834abc', at: NaN, toBe: 0xd834 },
+  { value: '\uD834abc', at: null, toBe: 0xd834 },
+  { value: '\uD834abc', at: undefined, toBe: 0xd834 },
+
+  // Lone low surrogates
+  { value: '\uDF06abc', at: '', toBe: 0xdf06 },
+  { value: '\uDF06abc', at: '_', toBe: 0xdf06 },
+  { value: '\uDF06abc', at: -1, toBe: undefined },
+  { value: '\uDF06abc', at: -0, toBe: 0xdf06 },
+  { value: '\uDF06abc', at: 0, toBe: 0xdf06 },
+  { value: '\uDF06abc', at: false, toBe: 0xdf06 },
+  { value: '\uDF06abc', at: NaN, toBe: 0xdf06 },
+  { value: '\uDF06abc', at: null, toBe: 0xdf06 },
+];
+
+describe('codePointAt (when String.codePointAt exist)', () => {
+  testCases.forEach(testCase => {
+    test(`codePointAt ${testCase.at} of ${testCase.value} should be ${testCase.toBe}`, () => {
+      expect(codePointAt(testCase.value, testCase.at)).toBe(testCase.toBe);
+    });
+  });
+});
+
+describe('codePointAt (when String.codePointAt does not exist)', () => {
+  testCases.forEach(testCase => {
+    test(`codePointAt ${testCase.at} of ${testCase.value} should be ${testCase.toBe}`, () => {
+      const aString = new String(testCase.value);
+
+      aString.codePointAt = undefined;
+
+      expect(codePointAt(aString, testCase.at)).toBe(testCase.toBe);
+    });
+  });
+});