Recently I was working on a legacy Java project without any unit tests. Just to get started I wanted to write some unit tests, so I could understand better what was happening in the code. But the code wasn't created to be easily unit tested. Therefore I had to resort to some Reflection API code to set the value of a static property of a class that was used in the code under test. Because the property is static we must pass null as an argument for the Reflection API Field.set() method.
package com.mrhaki.java;
public class MainTest {
@org.junit.Test
public void main_success() {
...
mockThreadLocal();
...
assertEquals("mrhaki", Holder.getValue());
}
private void mockThreadLocal() {
ThreadLocal mockThreadLocal = new ThreadLocal<String>();
mockThreadLocal.set("mrhaki");
Field threadLocalField = Holder.class.getDeclaredField("valueThreadLocal");
threadLocalField.setAccessible(true);
threadLocalField.set(null, mockThreadLocal);
}
}
package com.mrhaki.java;
public class Holder {
private static ThreadLocal<String> valueThreadLocal = new ThreadLocal<String>();
public static String getValue() {
return valueThreadLocal.get();
}
}
