java-有时返回字符串且有时返回null时如何使用Assert.assertEquals

Question

This is my first question on StackOverflow and I'm a complete beginner so I apologize if my question is vague

I have a method that will sometimes return a String and sometimes return null.

public String confirmLogo() {
String logo = null;

if(sql.getLogo(ID).equals("Qwerty Logo")
logo += "Qwerty Logo";

return logo;
}

So sometimes "qwerty logo" will be returned and sometimes it will return null.

Then in a test class, I'm trying to confirm that whats returned matched whats expected.

String primaryLogo = getLogoName(ID);
Assert.assert.equals(primaryLogo, example.confirmLogo());

I'm understandably getting NPEs (java.lang.NullPointerException) returned but I was wondering how I can accomplish this or if someone can't point me to an appropriate reference.

Answer 1

Your test should be predictable I would use two different tests to test this, one that expects null and one that doesn't. Use different input parameters to achieve the desired behavior (eg once provide x = "test" , and in other use x = "other" ).

Unless you really have eg a Math.random() in the method :)

Answer 2

You can find a reference for the Assert class here.

When it is exepcted to return null, you can use assertNull. When it isn't, you can use assertNotNull before you assertEquals -- avoiding the NPE.

Answer 3

According to the JavaDoc of Assert.assertEquals() ( http://junit.sourceforge.net/javadoc/org/junit/Assert.html#assertEquals(java.lang.Object,%20java.lang.Object) )

Asserts that two objects are equal. If they are not, an AssertionError without a message is thrown. If expected and actual are null, they are considered equal .

you should never get a NullPointerException from calling Assert.assertEquals() .