Java MockMvc Test and Match Json String

isIn is not for comparing strings, but arrays.

You can compare JSON as Map, with jackson-databind and Google Guava:

import static org.assertj.core.api.Assertions.assertThat;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.collect.Maps;
import java.util.List;
import java.util.Map;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.annotation.IfProfileValue;
import org.springframework.test.context.ActiveProfiles;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.MvcResult;

@SpringBootTest(classes = TestApplication.class)
@ActiveProfiles("dev")
@AutoConfigureMockMvc

public class SwStatusCheckTest {

    @Autowired
    private MockMvc mvc;

    @IfProfileValue(name = "spring.profiles.active", values = { "dev" })
    @Test
    @DisplayName("GET Method /SwCheckStatus check success")
    public void testStatusSuccess() throws Exception {

        MvcResult result = mvc.perform(get("/status/SwCheckStatus"))
            .andDo(print())
            .andExpect(status().isOk())
            .andReturn();
        //.andExpect(content().json("{\"services\":[\"OutboundMessageService\"]}", true));

        ObjectMapper mapper = new ObjectMapper();

        List<? extends Map<String, Object>> actualJson = mapper.readValue(result.getResponse().getContentAsString(),
            List.class);

        Map<String, Object> expected = Map.of("instanceName", "", "read", 1, "swProduct", "Area 1", "swProductModule",
            "Regular 1");

        boolean contains = false;
        for (Map<String, Object> a : actualJson) {
            boolean res = Maps.difference(a, expected).areEqual();
            if (res) {
                contains = true;
                break;
            }
        }
        assertThat(contains).isTrue();
    }
}

If I'm reading your question right as well as the image you posted, the problem is either the expected/actual Strings or the condition (assertion) defined in the test. The "actual" String value is an array of several elements, the "expected" is an array of only one element. Since the array of just one element is NOT contained in the array of several elements, it won't work.

If the code is changed such that the "expected" value you're looking for is written as JUST the object (without its enclosing array)

{ ... your object here ... }

Then the expected "isIn" actual assertion should work.