Add _.spread tests for the start param.

test/test.js

@@ -18577,11 +18577,15 @@
   QUnit.module('lodash.spread');
 
   (function() {
+    function fn(a, b, c) {
+      return slice.call(arguments);
+    }
+
     QUnit.test('should spread arguments to `func`', function(assert) {
       assert.expect(1);
 
-      var spread = _.spread(add);
+      var spread = _.spread(fn);
-      assert.strictEqual(spread([4, 2]), 6);
+      assert.deepEqual(spread([4, 2]), [4, 2]);
     });
 
     QUnit.test('should accept a falsey `array` argument', function(assert) {
@@ -18611,6 +18615,34 @@
       spread([4, 2], 'ignored');
       assert.deepEqual(args, [4, 2]);
     });
+
+    QUnit.test('should work with `start`', function(assert) {
+      assert.expect(1);
+
+      var spread = _.spread(fn, 1);
+      assert.deepEqual(spread(1, [2, 3, 4]), [1, 2, 3, 4]);
+    });
+
+    QUnit.test('should treat `start` as `0` for negative or `NaN` values', function(assert) {
+      assert.expect(1);
+
+      var values = [-1, NaN, 'a'],
+          expected = lodashStable.map(values, lodashStable.constant([1, 2, 3, 4]));
+
+      var actual = lodashStable.map(values, function(value) {
+        var spread = _.spread(fn, value);
+        return spread([1, 2, 3, 4]);
+      });
+
+      assert.deepEqual(actual, expected);
+    });
+
+    QUnit.test('should coerce `start` to an integer', function(assert) {
+      assert.expect(1);
+
+      var spread = _.spread(fn, 1.6);
+      assert.deepEqual(spread(1, [2, 3]), [1, 2, 3]);
+    });
   }());
 
   /*--------------------------------------------------------------------------*/