updated test case

YYModelTests/YYTestModelMapper.m

@@ -253,4 +253,15 @@
     XCTAssertTrue([[model.mArray firstObject] isKindOfClass:[YYTestPropertyMapperModelAuto class]]);
 }
 
+- (void)testForCodeCoverage {
+    Class cls = NSClassFromString(@"_YYModelPropertyMeta");
+    [cls new];
+    
+    cls = NSClassFromString(@"_YYModelMeta");
+    [cls new];
+    
+    cls = NSClassFromString(@"YYClassInfo");
+    [cls new];
+}
+
 @end