Add _.isSymbol tests.

test/test.js

@@ -10066,6 +10066,61 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('lodash.isSymbol');
+
+  (function() {
+    var args = arguments;
+
+    QUnit.test('should return `true` for symbols', function(assert) {
+      assert.expect(2);
+
+      if (Symbol) {
+        assert.strictEqual(_.isSymbol(symbol), true);
+        assert.strictEqual(_.isSymbol(Object(symbol)), true);
+      }
+      else {
+        skipTest(assert, 2);
+      }
+    });
+
+    QUnit.test('should return `false` for non-symbols', function(assert) {
+      assert.expect(12);
+
+      var expected = lodashStable.map(falsey, lodashStable.constant(false));
+
+      var actual = lodashStable.map(falsey, function(value, index) {
+        return index ? _.isSymbol(value) : _.isSymbol();
+      });
+
+      assert.deepEqual(actual, expected);
+
+      assert.strictEqual(_.isSymbol(args), false);
+      assert.strictEqual(_.isSymbol([1, 2, 3]), false);
+      assert.strictEqual(_.isSymbol(true), false);
+      assert.strictEqual(_.isSymbol(new Date), false);
+      assert.strictEqual(_.isSymbol(new Error), false);
+      assert.strictEqual(_.isSymbol(_), false);
+      assert.strictEqual(_.isSymbol(slice), false);
+      assert.strictEqual(_.isSymbol({ '0': 1, 'length': 1 }), false);
+      assert.strictEqual(_.isSymbol(1), false);
+      assert.strictEqual(_.isSymbol(/x/), false);
+      assert.strictEqual(_.isSymbol('a'), false);
+    });
+
+    QUnit.test('should work with symbols from another realm', function(assert) {
+      assert.expect(1);
+
+      if (Symbol && realm.symbol) {
+        assert.strictEqual(_.isSymbol(realm.symbol), true);
+      }
+      else {
+        skipTest(assert);
+      }
+    });
+  }(1, 2, 3));
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('lodash.isTypedArray');
 
   (function() {