Gradle test fails with OutOfMemory when run together BUT passes when run individually

I have tried everything to try at least understand why this is happening even if I can't solve it.

I have the following integration test which is part of a larger test suite of 893 tests:

@SpringBootTest
@ExtendWith(SpringExtension.class)
@AutoConfigureMockMvc
@ActiveProfiles("test")
@Import(OracleTestDbConfig.class)
public class StyleCCIntegrationTest {

    @Autowired
    MockMvc mockMvc;

    @MockBean
    CustomerChoiceRepository customerChoiceRepository;
    private StyleCCTestUtility styleCCTestUtility;
    @Autowired
    ObjectMapper objectMapper;
    @MockBean
    PriceStrategyClient priceStrategyClient;
    @MockBean
    MerchandiseHierarchyService merchandiseHierarchyService;
    @MockBean
    StyleRepository styleRepository;
    @MockBean
    RegionRepository regionRepository;
    @MockBean
    AsyncService asyncService;

    @Nested
    class StyleCCRequest {

        private static final String STYLE_CC_BASE_URL = "/items/styleCCDetails";

        @BeforeEach
        void setup() {
            styleCCTestUtility = new StyleCCTestUtility();
        }

        @Test
        void shouldReturn200WhenValidStyleCCRequestPassed() throws Exception {
            mockDbAndApiInteractionForStyleCC();
            mockMvc.perform(MockMvcRequestBuilders.post(STYLE_CC_BASE_URL)
                    .contentType(MediaType.APPLICATION_JSON)
                    .content(objectMapper.writeValueAsString(styleCCTestUtility
                            .createStyleCCRequestForCCIdForIT())))
                    .andExpect(status().isOk());
        }

        @Test
        void shouldReturnErrorWhenNoCustomerChoiceStyleFound() throws Exception {
            mockDbAndApiInteractionForStyleCCForNoData();
            mockMvc.perform(MockMvcRequestBuilders.post(STYLE_CC_BASE_URL)
                    .contentType(MediaType.APPLICATION_JSON)
                    .content(objectMapper.writeValueAsString(styleCCTestUtility.createStyleCCRequestForCCId())))
                    .andExpect(status().isNotFound()).andReturn();
        }

        @Test
        void shouldReturnErrorWhenApiNotAvailableForStyleCC() throws Exception {
            when(priceStrategyClient.getPriceStrategyIdsByBMC(anyString(), anyString(), anyString()))
                    .thenAnswer(invocation -> {
                        throw new ItemRuntimeException(ItemExceptions.PRICE_STRATEGY_EXCEPTION);
                    });
            mockMvc.perform(MockMvcRequestBuilders.post(STYLE_CC_BASE_URL)
                    .contentType(MediaType.APPLICATION_JSON)
                    .content(objectMapper.writeValueAsString(styleCCTestUtility.createStyleCCRequestForCCId())))
                    .andExpect(status().isNotFound());
        }

        @Test
        void shouldReturnErrorWhenDbNotReachableForStyleCC() throws Exception {
            when(priceStrategyClient.getPriceStrategyIdsByBMC(anyString(), anyString(), anyString()))
                    .thenReturn(styleCCTestUtility.createPriceStrategyIds());
            when(customerChoiceRepository.findByPriceStrategyIdInAndId(any(), any()))
                    .thenAnswer(invocation -> {
                        throw new ItemRuntimeException(ItemExceptions.GENERAL_ERROR);
                    });
            mockMvc.perform(MockMvcRequestBuilders.post(STYLE_CC_BASE_URL)
                    .contentType(MediaType.APPLICATION_JSON)
                    .content(objectMapper.writeValueAsString(styleCCTestUtility.createStyleCCRequestForCCId())))
                    .andExpect(status().isInternalServerError());
        }

        private void mockDbAndApiInteractionForStyleCC() {
            when(customerChoiceRepository
                    .findByPriceStrategyIdInAndId(any(), any()))
                    .thenReturn(styleCCTestUtility.getCustomerChoices());
            when(merchandiseHierarchyService.getHierarchyDesc(any()))
                    .thenReturn(styleCCTestUtility.createHierarchyIds());
            when(styleRepository.findByIdInAndPriceStrategyIdIn(any(), (List<Long>) any()))
                    .thenReturn(styleCCTestUtility.getStyles());
            when(regionRepository.findByPriceStrategyIdAndStyleId(any(), anyString()))
                    .thenReturn(styleCCTestUtility.createRegionList());
            when(priceStrategyClient.getPriceStrategyIdsByBMC(anyString(), anyString(), anyString()))
                    .thenReturn(singletonList(1L));
        }

        private void mockDbAndApiInteractionForStyleCCForNoData() {
            when(priceStrategyClient.getPriceStrategyIdsByBMC(anyString(), anyString(), anyString()))
                    .thenReturn(styleCCTestUtility.createPriceStrategyIds());
            when(customerChoiceRepository
                    .findByPriceStrategyIdInAndId(any(), any())).thenReturn(emptyList());
            when(styleRepository.findByIdInAndPriceStrategyIdIn(any(), (List<Long>) any()))
                    .thenReturn(emptyList());
            when(regionRepository.findByPriceStrategyIdAndStyleId(any(), anyString()))
                    .thenReturn(emptyList());
            when(merchandiseHierarchyService.getHierarchyDesc(any()))
                    .thenReturn(MerchandiseHierarchy.builder().build());
        }
    }
}

When I try to run this test with :

./gradlew clean test

It fails when running test number 193 which is the above test, and it always fails at the same point in the same way saying that:

<==========---> 83% EXECUTING [9m 16s]
> :test > 193 tests completed, 19 failed
> :test > Executing test com.pem.item.integration.StyleCCIntegrationTest
> :test > Executing test com...integration.StyleCCIntegrationTest$StyleCCRequest
Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "pem.item.service.exchange.allocation-79"

Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "pem.item.service.exchange.order-78"

Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "pem.item.service.exchange.planning-88"

Exception: java.lang.OutOfMemoryError thrown from the UncaughtExceptionHandler in thread "pem.item.service.exchange.allocation-89"

But when I run the test individually everything works, as it should, because there is nothing in the test that is really fancy.

I don't know what to do, what else I can change, or even where to look to pinpoint this cause. What can I try next?

Also when this test is hit then my CPU utilisation goes up to 90% for some reason.

The OutOfMemoryError is thrown by the TestEventLogger

2021-12-03T11:44:27.897+0530 [DEBUG] [TestEventLogger]     Exception in thread "pem.item.service.exchange.planning-101" java.lang.OutOfMemoryError: Java heap space