feat(rtts_assert): avoid deep recursion in prettyPrint

modules/rtts_assert/test/rtts_assert_spec.es6

@@ -14,6 +14,33 @@
 
 export function main() {
 
+describe('prettyPrint', () => {
+  class Type {};
+
+  it('should limit the number of printed properties', () => {
+    var o = {};
+    for (var i = 0; i < 100; i++) {
+      o['p_' + i] = i;
+    }
+    try {
+      assert.type(o, Type);
+      throw 'fail!';
+    } catch (e) {
+      expect(e.message.indexOf('p_0')).toBeGreaterThan(-1);
+      expect(e.message.indexOf('...')).toBeGreaterThan(-1);
+      expect(e.message.indexOf('p_20')).toBe(-1);
+    }
+  });
+
+  it('should limit the depth of printed properties', () => {
+    var o = {l1: {l2: {l3: {l4: {l5: {l6: 'deep'}}}}}};
+
+    expect(() => {
+      assert.type(o, Type);
+    }).toThrowError('Expected an instance of Type, got {l1: {l2: {l3: {l4: [...]}}}}!');
+  });
+});
+
 // ## Basic Type Check
 // By default, `instanceof` is used to check the type.
 //