Hamcrest Matcher

As a follow up to the Hamcrest post I made yesterday, I wanted to post an example of my own Hamcrest matcher implementation. This matcher tests if a string contains a specified number of substrings.
An example usage could be:

    String sql = "select a,b,c from tableA";
    assertThat(sql, hasNumberOfSubstrings(",", 2));

See the source code below. I have been reading up on OSS licenses recently and decided to release this using the same license as Hamcrest – the new BSD license.

I have also attached a jar which includes the associated unit tests, although you will need the hamcrest-unit-test project to compile, which can be downloaded as part of the hamcrest all-in-one jar.

package com.shaunabram.hamcrest;

import java.util.regex.Pattern;
import org.hamcrest.*;

/**
 * Matcher which tests if a string contains a specified number of substrings.
 * 
 * @author sabram
 */
public class HasNumberOfSubstrings extends TypeSafeMatcher {

    private final String substring;
    private final int count;

    public HasNumberOfSubstrings(String substring, int count) {
        this.substring = substring;
        this.count = count;
    }
    
    @Override
    protected boolean matchesSafely(String item) {
        Pattern p = Pattern.compile(substring);
        java.util.regex.Matcher m = p.matcher(item);
        int actualCount = 0;
        while (m.find()) {
            actualCount++;
        }
        if (actualCount == count) return true;
        else return false;
    }

    public void describeTo(Description description) {
        description.appendText("String containing ")
            .appendText(count + " occurences of ")
            .appendText(substring);
        
    }
    
    @Override
    public void describeMismatchSafely(String item, Description mismatchDescription) {
      mismatchDescription.appendValue(count)
                         .appendText(" occurence(s) of ") 
                         .appendValue(substring)
                         .appendText(" in ")
                         .appendText(item);
    }
    
    @Factory
    public static Matcher hasNumberOfSubstrings(String substring, int count) {
        return new HasNumberOfSubstrings(substring, count);
    }
    
}

Tags: Hamcrest, JUnit, Testing, unittesting