due to @ChildResourceFromRequest my unit test cases are getting failed while writing unit testcases for AEM component

hi , all my testcases are getting failed showing runtime exception if I am including @ChildResourceFromRequest in my model class .

Model class : 

package comcore.models.components.content.collections.locations;

import com.adobe.acs.commons.models.injectors.annotation.ChildResourceFromRequest;
import com.core.configurations.GoogleMapAPIConfiguration;
import com.core.decorators.Validatable;
import com.core.models.components.ComponentModel;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.commons.lang3.StringUtils;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.models.annotations.DefaultInjectionStrategy;
import org.apache.sling.models.annotations.Model;
import org.apache.sling.models.annotations.injectorspecific.ChildResource;
import org.apache.sling.models.annotations.injectorspecific.OSGiService;
import org.apache.sling.models.annotations.injectorspecific.ValueMapValue;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.annotation.Nonnull;
import javax.annotation.PostConstruct;
import java.util.List;
import static java.util.Collections.emptyList;

@Model(
    adaptables = SlingHttpServletRequest.class,
    defaultInjectionStrategy = DefaultInjectionStrategy.OPTIONAL)
public class LocationsModel extends ComponentModel implements Validatable {
  private static final Logger log = LoggerFactory.getLogger(LocationsModel.class);
  private static final String CSS_CLASS_NAME = "locations";

  @OSGiService
  private GoogleMapAPIConfiguration mapAPIConfiguration;

  @ValueMapValue
  private String title;

  @ValueMapValue
  private int zoomLevel;
  
  //@ChildResourceFromRequest
  @ChildResource // USING THIS AS ALTERNATIVE BUT NOT SURE IF IT WILL CHANGE THE FUNCTIONALITY
  private final List<LocationItem> locations = emptyList();

  private String locationsJson;
  private String key;

  @PostConstruct
  protected void init() {
    if (mapAPIConfiguration != null) {
      this.key = mapAPIConfiguration.getKey();
    }
/* I NEED TO COMMENT THIS CODE IN ORDER AVOID ERROR
    try {
      this.locationsJson = new ObjectMapper().writeValueAsString(this.locations);
    } catch (Exception ex) {
      log.error("Unable to generate locations to JSON string", ex);
    }
*/


  }

  @Nonnull
  @Override
  public String getCssClassName() {
    return CSS_CLASS_NAME;
  }

  @Override
  public boolean isValid() {
    return StringUtils.isNotEmpty(this.key) && !this.locations.isEmpty();
  }

  public String getTitle() {
    return this.title;
  }

  @Nonnull
  public List<LocationItem> getLocations() {
    return this.locations;
  }

  public String getLocationsJson() {
    return this.locationsJson;
  }

  public int getZoomLevel() {
    return this.zoomLevel;
  }

  public String getKey() {
    return this.key;
  }
}

can you tell me why @ChildResourceFromRequest is not working 

Thank you