In this tutorial, you will learn how to create a custom ResultMatcher for MockMvc, to suit your project needs.<\/p>\n\n\n\n
Imagine you are testing an API and the response contains a date. And you want to check if the response date is valid.<\/p>\n\n\n\n
So you have a test assertion that checks for an exact date and time. But for some reason, this result can vary over time. For some reasons:<\/p>\n\n\n\n
Clock<\/code>.<\/li>\n\n\n\n- Or any specific other date manipulation or configuration that your project has.<\/li>\n<\/ul>\n\n\n\n
When you run your tests you get errors like this, you check for the LocalDateTime.now()<\/code> but the result is a few seconds later.<\/p>\n\n\n\nExpected: is "2024-01-11T12:37:03.1"\nbut: was "2024-01-11T12:38:21.1"\n\n<\/pre><\/div>\n\n\nOr you have a time zone issue that makes everything 3 hours behind:<\/p>\n\n\n
\nExpected: is "2023-03-07T20:18:57"\nbut: was "2023-03-07T17:18:57"\n\n<\/pre><\/div>\n\n\nOne solution for that (there are more solutions, maybe some better ones) is to create a custom ResultMatcher. That can check if the result date from an API response is in a range.<\/p>\n\n\n\n
How to use a custom result matcher to fix this issue?<\/h2>\n\n\n\n
If we are checking the MockMvc the code should look like this:<\/p>\n\n\n
\nmvc.perform(get("\/product\/{}",productId).contentType(MediaType.APPLICATION_JSON_UTF8))\n .andExpect(status().isOk())\n .andExpect(jsonPath("$.date", is("2023-03-07T17:18:57")));\n\n<\/pre><\/div>\n\n\nAs we said, the problem with this implementation is that the assertion is by the exact date and time.<\/p>\n\n\n\n
And our time can vary a little bit, so it\u2019ll break our test.<\/p>\n\n\n\n
Writing a custom result matcher will enable you to do custom checks as you need.<\/p>\n\n\n\n
You can write a result matcher that checks if the response date is in a range that you specify.<\/p>\n\n\n\n
Example of a custom result matcher for date range validation:<\/h3>\n\n\n\npublic static ResultMatcher isDateTimeInRange(String path, String startDateStr, String endDateStr) {\n LocalDateTime startDate = LocalDateTime.parse(startDateStr, formatter);\n LocalDateTime endDate = LocalDateTime.parse(endDateStr, formatter);\n return mvcResult -> {\n String contentAsString = mvcResult.getResponse().getContentAsString();\n LocalDateTime checkoutDate = LocalDateTime.parse(JsonPath.read(contentAsString, path), formatter);\n if (!(checkoutDate.isAfter(startDate) && checkoutDate.isBefore(endDate))) {\n throw new AssertionError(String.format("Date: %s is not between %s and %s", checkoutDate, startDate, endDate));\n }\n };\n }\n\n<\/pre><\/div>\n\n\nThis code allows us to send a start and end range and the date format for the date we\u2019re working.<\/p>\n\n\n\n
This will enable us to write our logic to check if the date is in range!<\/p>\n\n\n\n
How to use your custom result matcher in your test<\/h3>\n\n\n\nmvc.perform(get("\/product\/{}",productId).contentType(MediaType.APPLICATION_JSON_UTF8))\n .andExpect(status().isOk())\n .andExpect(isDateTimeInRange("$.date",\n "2019-03-07T13:18:57",\n "2019-03-07T21:18:57",\n "yyyy-MM-dd'T'HH:mm:ss"));\n\n<\/pre><\/div>\n\n\nThis will check if the response date is in the range requested!<\/p>\n\n\n\n
By the way, this is only one example of how to create a custom result matcher.<\/p>\n\n\n\n
Explore the possibilities and create some that suit your needs.<\/p>\n\n\n\n
Happy coding!<\/p>\n\n\n\n
Follow me on social media:<\/p>\n\n\n\n
Willian Moya (@WillianFMoya) \/ X (twitter.com)<\/a><\/p>\n\n\n\n