Make Hamcrest to match a key or value in a Map

[albert kao]

I wrote this test program for Hamcrest and Map to use Hamcrest Matchers.

This program use Hamcrest as standalone (does not use JUnit).

Why none of the output is true (matched)?

How to modify this test program so that a key or value in a Map is matched (output is true)?

import java.util.Map;

import java.util.stream.Collectors;

import java.util.stream.Stream;

import org.hamcrest.Matchers;

import org.hamcrest.collection.IsMapContaining;

public class TestMap {

public static void main(String[] args) {

Map<String, Integer> map = Stream.of(new Object[][] { 

{ "data1", 1 }, 

{ "data2", 2 }, 

}).collect(Collectors.toMap(data -> (String) data[0], data -> (Integer) data[1]));

for (Map.Entry<String, Integer> entry : map.entrySet()) {

System.out.println("Matchers.hasKey(\"data1\") " + Matchers.hasKey("data1").matches("data1"));

System.out.println("Matchers.hasValue(1) " + Matchers.hasValue(1).matches(1));

System.out.println("IsMapContaining.hasKey(\"data1\") " + IsMapContaining.hasKey("data1").matches("data1"));

System.out.println("IsMapContaining.hasValue(1) " + IsMapContaining.hasValue(1).matches(1));

System.out.println("IsMapContaining.hasEntry(entry.getKey(), entry.getValue()) " + IsMapContaining.hasEntry(entry.getKey(), entry.getValue()));

}

}

}

The output is:

Matchers.hasKey("data1") false

Matchers.hasValue(1) false

IsMapContaining.hasKey("data1") false

IsMapContaining.hasValue(1) false

IsMapContaining.hasEntry(entry.getKey(), entry.getValue()) map containing ["data2"-><2>]

Matchers.hasKey("data1") false

Matchers.hasValue(1) false

IsMapContaining.hasKey("data1") false

IsMapContaining.hasValue(1) false

IsMapContaining.hasEntry(entry.getKey(), entry.getValue()) map containing ["data1"-><1>]

[Steve Freeman]

I’m not sure I understand your code, but it looks like you’re trying to match a value rather than a map.

For example, I think the first check should be 

System.out.println("Matchers.hasKey(\"data1\") " + Matchers.hasKey("data1").matches(map));

In practice this would be used as:

assertThat(map, hasKey(“data1”));

which is how it is intended to read.