fest和assert-j之间的细微差别

Question

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import org.junit.Before;
import org.junit.Test;

class MyMap implements Map<String, Object> {
    private Map<String, Object> theMap = new HashMap<>();

    @Override
    public int size() {
        return theMap.size();
    }

    @Override
    public boolean isEmpty() {
        return theMap.isEmpty();
    }

    @Override
    public boolean containsKey(Object key) {
        return theMap.containsKey(key);
    }

    @Override
    public boolean containsValue(Object value) {
        return theMap.containsValue(value);
    }

    @Override
    public Object get(Object key) {
        return theMap.get(key);
    }

    @Override
    public Object put(String key, Object value) {
        return theMap.put(key, value);
    }

    @Override
    public Object remove(Object key) {
        return theMap.remove(key);
    }

    @Override
    public void putAll(Map<? extends String, ? extends Object> m) {
        theMap.putAll(m);
    }

    @Override
    public void clear() {
        theMap.clear();
    }

    @Override
    public Set<String> keySet() {
        return theMap.keySet();
    }

    @Override
    public Collection<Object> values() {
        return theMap.values();
    }

    @Override
    public Set<java.util.Map.Entry<String, Object>> entrySet() {
        return theMap.entrySet();
    }
}

public class TestMapComparison {
    private Map<String, Object> m1 = new HashMap<>();
    private MyMap m2 = new MyMap();

    @Before
    public void before() {
        m1.put("a", "b");
        m2.put("a", "b");
    }

    // Fails with:
    // java.lang.AssertionError:
    // expected: <'{'a'='b'} (MyMap@6f5fc7ad)'>
    // but was: <'{'a'='b'} (HashMap@3)'>
    @Test
    public void test1_Fest_m1_isEqualTo_m2() {
        org.fest.assertions.api.Assertions.assertThat(m1).isEqualTo(m2);
    }

    @Test // Pass
    public void test2_AssertJ_m1_isEqualTo_m2() {
        org.assertj.core.api.Assertions.assertThat(m1).isEqualTo(m2);
    }

    @Test // Pass
    public void test3_Fest_m2_isEqualTo_m1() {
        org.fest.assertions.api.Assertions.assertThat(m2).isEqualTo(m1);
    }

    // Fails with:
    // java.lang.AssertionError:
    // Expecting: <"{"a"="b"} (MyMap@5aedacd2)">
    // to be equal to:
    // <"{"a"="b"} (HashMap@3)"> but was not.
    @Test
    public void test4_AssertJ_m2_isEqualTo_m1() {
        org.assertj.core.api.Assertions.assertThat(m2).isEqualTo(m1);
    }
}

Answer 1

好吧，错误在您的代码中，如果您测试equals（）的契约，每个库都会发现错误，wich必须是对称的：A等于B iff B等于A。

我会简单地修复您的代码，并很高兴通过迁移发现了bug。我也会改进测试

assertThat(a).isEqualTo(b);
assertThat(b).isEqualTo(a);

以确保合同得到履行。