LibJS: Implement get Intl.Collator.prototype.compare

Userland/Libraries/LibJS/Tests/builtins/Intl/Collator/Collator.prototype.compare.js

@@ -0,0 +1,41 @@
+describe("correct behavior", () => {
+    test("length is 2", () => {
+        expect(new Intl.Collator().compare).toHaveLength(2);
+    });
+
+    test("basic functionality", () => {
+        const collator = new Intl.Collator();
+        expect(collator.compare("", "")).toBe(0);
+        expect(collator.compare("a", "a")).toBe(0);
+        expect(collator.compare("6", "6")).toBe(0);
+
+        function compareBoth(a, b) {
+            const aTob = collator.compare(a, b);
+            const bToa = collator.compare(b, a);
+
+            expect(aTob > 0).toBeTrue();
+            expect(aTob).toBe(-bToa);
+        }
+
+        compareBoth("a", "");
+        compareBoth("1", "");
+        compareBoth("a", "A");
+        compareBoth("7", "3");
+        compareBoth("0000", "0");
+
+        expect(collator.compare("undefined")).toBe(0);
+        expect(collator.compare("undefined", undefined)).toBe(0);
+
+        expect(collator.compare("null", null)).toBe(0);
+        expect(collator.compare("null", undefined)).not.toBe(0);
+        expect(collator.compare("null") < 0).toBeTrue();
+    });
+
+    test("UTF-16", () => {
+        const collator = new Intl.Collator();
+        const string = "😀😀";
+        expect(collator.compare(string, "😀😀")).toBe(0);
+        expect(collator.compare(string, "\ud83d") > 0);
+        expect(collator.compare(string, "😀😀s") < 0);
+    });
+});