Round Infinity with a precision argument returns Infinity (#4272)

* Round Infinity with a precision argument returns Infinity

* Also making sure this is true for -Infinity
* Tested with _.round(), _.floor() and _.ceil()

* Switch to using isFinite to check if number should be rounded

* Add tests for rounding NaN now that there is an isFinite check

test/test.js

@@ -19810,6 +19810,74 @@
 
       assert.deepEqual(actual, expected);
     });
+
+    QUnit.test('`_.' + methodName + '` should return `Infinity` given `Infinity` regardless of `precision`', function(assert) {
+      assert.expect(6);
+
+      var actual = func(Infinity);
+      assert.strictEqual(actual, Infinity);
+
+      actual = func(Infinity, 0)
+      assert.strictEqual(actual, Infinity);
+
+      actual = func(Infinity, 2)
+      assert.strictEqual(actual, Infinity);
+
+      actual = func(Infinity, -2)
+      assert.strictEqual(actual, Infinity);
+
+      actual = func(Infinity, 2);
+      assert.strictEqual(actual, isFloor ? Infinity : Infinity);
+
+      actual = func(Infinity, 2);
+      assert.strictEqual(actual, isCeil ? Infinity : Infinity);
+    });
+
+    QUnit.test('`_.' + methodName + '` should return `-Infinity` given `-Infinity` regardless of `precision`', function(assert) {
+      assert.expect(6);
+
+      var actual = func(-Infinity);
+      assert.strictEqual(actual, -Infinity);
+
+      actual = func(-Infinity, 0)
+      assert.strictEqual(actual, -Infinity);
+
+      actual = func(-Infinity, 2)
+      assert.strictEqual(actual, -Infinity);
+
+      actual = func(-Infinity, -2)
+      assert.strictEqual(actual, -Infinity);
+
+      actual = func(-Infinity, 2);
+      assert.strictEqual(actual, isFloor ? -Infinity : -Infinity);
+
+      actual = func(-Infinity, 2);
+      assert.strictEqual(actual, isCeil ? -Infinity : -Infinity);
+    });
+
+    QUnit.test('`_.' + methodName + '` should return `NaN` given `NaN` regardless of `precision`', function(assert) {
+      assert.expect(6);
+
+      var actual = func(NaN)
+      assert.deepEqual(actual, NaN);
+
+      actual = func(NaN, 0)
+      assert.deepEqual(actual, NaN);
+
+      actual = func(NaN, 2)
+      assert.deepEqual(actual, NaN);
+
+      actual = func(NaN, -2)
+      assert.deepEqual(actual, NaN);
+
+      actual = func(NaN, 2);
+      assert.deepEqual(actual, isFloor ? NaN : NaN);
+
+      actual = func(NaN, 2);
+      assert.deepEqual(actual, isCeil ? NaN : NaN);
+    });
+
+
   });
 
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