如何断言Map包含带有条目的Map

Question

我有一个单元测试,需要检查嵌套的映射值.我可以通过拉出条目并匹配底层来让我的断言工作Map,但我正在寻找一种明确的方式来显示断言正在做什么.这是一个非常简化的测试:

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.hasEntry;

import java.util.HashMap;
import java.util.Map;

import org.junit.Test;

public class MapContainsMapTest {
    @Test
    public void testMapHasMap() {
        Map<String, Object> outerMap = new HashMap<String, Object>();
        Map<String, Object> nestedMap = new HashMap<String, Object>();
        nestedMap.put("foo", "bar");
        outerMap.put("nested", nestedMap);

        // works but murky
        assertThat((Map<String, Object>) outerMap.get("nested"), hasEntry("foo", "bar"));
        // fails but clear
        assertThat(outerMap, hasEntry("nested", hasEntry("foo", "bar")));
    }
}

似乎问题是外部地图正在使用,hasEntry(K key, V value)而我想要使用的是hasEntry(Matcher<? super K> keyMatcher, Matcher<? super V> valueMatcher).我不知道如何强制断言使用第二种形式.

提前致谢.

Answer 1

如果你声明了outerMap，因为Map<String, Map<String, Object>>你不需要丑陋的演员表。像这样：

public class MapContainsMapTest {

    @Test
    public void testMapHasMap() {
        Map<String, Map<String, Object>> outerMap = new HashMap<>();
        Map<String, Object> nestedMap = new HashMap<>();
        nestedMap.put("foo", "bar");
        outerMap.put("nested", nestedMap);

        assertThat(outerMap.get("nested"), hasEntry("foo", "bar"));
    }
}

Answer 2

如果只想将Map<String, Object>值作为值放入，请相应地outerMap调整声明。那你可以做

@Test
public void testMapHasMap() {
    Map<String, Map<String, Object>> outerMap = new HashMap<>();
    Map<String, Object> nestedMap = new HashMap<String, Object>();
    nestedMap.put("foo", "bar");
    outerMap.put("nested", nestedMap);

    Object value = "bar";
    assertThat(outerMap, hasEntry(equalTo("nested"), hasEntry("foo", value)));  
}

Object value = "bar";由于编译原因是必需的。或者，您可以使用

assertThat(outerMap,
   hasEntry(equalTo("nested"), Matchers.<String, Object> hasEntry("foo", "bar")));

Answer 3

我可能会为此扩展一个新的 Matcher，类似的东西（注意，NPE 潜伏）：

class SubMapMatcher extends BaseMatcher<Map<?,?>> {

private Object key;
private Object subMapKey;
private Object subMapValue;

public SubMapMatcher(Object key, Object subMapKey, Object subMapValue) {
    super();
    this.key = key;
    this.subMapKey = subMapKey;
    this.subMapValue = subMapValue;
}

@Override
public boolean matches(Object item) {

    Map<?,?> map = (Map<?,?>)item;

    if (!map.containsKey(key)) {
        return false;
    }

    Object o = map.get(key);

    if (!(o instanceof Map<?,?>)) {
        return false;
    }

    Map<?,?> subMap = (Map<?,?>)o;
    return subMap.containsKey(subMapKey) && subMap.get(subMapKey).equals(subMapValue);
}

@Override
public void describeTo(Description description) {
    description.appendText(String.format("contains %s -> %s : %s", key, subMapKey, subMapValue));
}

public static SubMapMatcher containsSubMapWithKeyValue(String key, String subMapKey, String subMapValue) {
    return new SubMapMatcher(key, subMapKey, subMapValue);
}

}